*luasnip.txt*             For NVIM v0.8.0             Last change: 2024 May 24

==============================================================================
Table of Contents                                  *luasnip-table-of-contents*

1. Basics                                                     |luasnip-basics|
  - Jump-Index                                     |luasnip-basics-jump-index|
  - Adding Snippets                           |luasnip-basics-adding-snippets|
  - Snippet Insertion                       |luasnip-basics-snippet-insertion|
2. Node                                                         |luasnip-node|
  - Api                                                     |luasnip-node-api|
3. Snippets                                                 |luasnip-snippets|
  - Data                                               |luasnip-snippets-data|
4. TextNode                                                 |luasnip-textnode|
5. InsertNode                                             |luasnip-insertnode|
6. FunctionNode                                         |luasnip-functionnode|
7. Node Reference                                     |luasnip-node-reference|
8. ChoiceNode                                             |luasnip-choicenode|
9. SnippetNode                                           |luasnip-snippetnode|
10. IndentSnippetNode                              |luasnip-indentsnippetnode|
11. DynamicNode                                          |luasnip-dynamicnode|
12. RestoreNode                                          |luasnip-restorenode|
13. Key Indexer                                          |luasnip-key-indexer|
14. Absolute Indexer                                |luasnip-absolute-indexer|
15. MultiSnippet                                        |luasnip-multisnippet|
16. Extras                                                    |luasnip-extras|
  - Lambda                                             |luasnip-extras-lambda|
  - Match                                               |luasnip-extras-match|
  - Repeat                                             |luasnip-extras-repeat|
  - Partial                                           |luasnip-extras-partial|
  - Nonempty                                         |luasnip-extras-nonempty|
  - Dynamic Lambda                             |luasnip-extras-dynamic-lambda|
  - FMT                                                   |luasnip-extras-fmt|
  - Conditions                                     |luasnip-extras-conditions|
  - On The Fly-Snippets                   |luasnip-extras-on-the-fly-snippets|
  - select_choice                               |luasnip-extras-select_choice|
  - Filetype-Functions                     |luasnip-extras-filetype-functions|
  - Postfix-Snippet                           |luasnip-extras-postfix-snippet|
  - Treesitter-Postfix-Snippet     |luasnip-extras-treesitter-postfix-snippet|
  - Snippet List                                 |luasnip-extras-snippet-list|
  - Snippet Location                         |luasnip-extras-snippet-location|
17. Extend Decorator                                |luasnip-extend-decorator|
18. LSP-Snippets                                        |luasnip-lsp-snippets|
  - Snipmate Parser                     |luasnip-lsp-snippets-snipmate-parser|
  - Transformations                     |luasnip-lsp-snippets-transformations|
19. Variables                                              |luasnip-variables|
  - Environment Namespaces          |luasnip-variables-environment-namespaces|
  - LSP-Variables                            |luasnip-variables-lsp-variables|
20. Loaders                                                  |luasnip-loaders|
  - Snippet-specific filetypes    |luasnip-loaders-snippet-specific-filetypes|
  - VS-Code                                          |luasnip-loaders-vs-code|
  - SNIPMATE                                        |luasnip-loaders-snipmate|
  - Lua                                                  |luasnip-loaders-lua|
  - edit_snippets                              |luasnip-loaders-edit_snippets|
21. SnippetProxy                                        |luasnip-snippetproxy|
22. ext_opts                                                |luasnip-ext_opts|
23. Docstrings                                            |luasnip-docstrings|
24. Docstring-Cache                                  |luasnip-docstring-cache|
25. Events                                                    |luasnip-events|
26. Cleanup                                                  |luasnip-cleanup|
27. Logging                                                  |luasnip-logging|
28. Source                                                    |luasnip-source|
29. Config-Options                                    |luasnip-config-options|
30. Troubleshooting                                  |luasnip-troubleshooting|
  - Adding Snippets                  |luasnip-troubleshooting-adding-snippets|
31. API                                                          |luasnip-api|
>
                __                       ____
               /\ \                     /\  _`\           __
               \ \ \      __  __     __ \ \,\L\_\    ___ /\_\  _____
                \ \ \  __/\ \/\ \  /'__`\\/_\__ \  /' _ `\/\ \/\ '__`\
                 \ \ \L\ \ \ \_\ \/\ \L\.\_/\ \L\ \/\ \/\ \ \ \ \ \L\ \
                  \ \____/\ \____/\ \__/.\_\ `\____\ \_\ \_\ \_\ \ ,__/
                   \/___/  \/___/  \/__/\/_/\/_____/\/_/\/_/\/_/\ \ \/
                                                                 \ \_\
                                                                  \/_/
<

LuaSnip is a snippet engine written entirely in Lua. It has some great features
like inserting text (`luasnip-function-node`) or nodes (`luasnip-dynamic-node`)
based on user input, parsing LSP syntax and switching nodes
(`luasnip-choice-node`). For basic setup like mappings and installing, check
the README.

All code snippets in this help assume the following:

>lua
    local ls = require("luasnip")
    local s = ls.snippet
    local sn = ls.snippet_node
    local isn = ls.indent_snippet_node
    local t = ls.text_node
    local i = ls.insert_node
    local f = ls.function_node
    local c = ls.choice_node
    local d = ls.dynamic_node
    local r = ls.restore_node
    local events = require("luasnip.util.events")
    local ai = require("luasnip.nodes.absolute_indexer")
    local extras = require("luasnip.extras")
    local l = extras.lambda
    local rep = extras.rep
    local p = extras.partial
    local m = extras.match
    local n = extras.nonempty
    local dl = extras.dynamic_lambda
    local fmt = require("luasnip.extras.fmt").fmt
    local fmta = require("luasnip.extras.fmt").fmta
    local conds = require("luasnip.extras.expand_conditions")
    local postfix = require("luasnip.extras.postfix").postfix
    local types = require("luasnip.util.types")
    local parse = require("luasnip.util.parser").parse_snippet
    local ms = ls.multi_snippet
    local k = require("luasnip.nodes.key_indexer").new_key
<

As noted in the |luasnip-loaders-lua|-section:


  By default, the names from `luasnip.config.snip_env`
  <https://github.com/L3MON4D3/LuaSnip/blob/master/lua/luasnip/config.lua#L22-L48>
  will be used, but it’s possible to customize them by setting `snip_env` in
  `setup`.
Furthermore, note that while this document assumes you have defined `ls` to be
`require("luasnip")`, it is **not** provided in the default set of variables.


==============================================================================
1. Basics                                                     *luasnip-basics*

In LuaSnip, snippets are made up of `nodes`. These can contain either

- static text (`textNode`)
- text that can be edited (`insertNode`)
- text that can be generated from the contents of other nodes (`functionNode`)
- other nodes
    - `choiceNode`: allows choosing between two nodes (which might contain more
        nodes)
    - `restoreNode`: store and restore input to nodes
- or nodes that can be generated based on input (`dynamicNode`).

Snippets are always created using the `s(trigger:string,
nodes:table)`-function. It is explained in more detail in |luasnip-snippets|,
but the gist is that it creates a snippet that contains the nodes specified in
`nodes`, which will be inserted into a buffer if the text before the cursor
matches `trigger` when `ls.expand` is called.


JUMP-INDEX                                         *luasnip-basics-jump-index*

Nodes that can be jumped to (`insertNode`, `choiceNode`, `dynamicNode`,
`restoreNode`, `snippetNode`) all require a "jump-index" so luasnip knows the
order in which these nodes are supposed to be visited ("jumped to").

>lua
    s("trig", {
        i(1), t"text", i(2), t"text again", i(3)
    })
<

These indices don’t "run" through the entire snippet, like they do in
textmate-snippets (`"$1 ${2: $3 $4}"`), they restart at 1 in each nested
snippetNode:

>lua
    s("trig", {
        i(1), t" ", sn(2, {
            t" ", i(1), t" ", i(2)
        })
    })
<

(roughly equivalent to the given textmate-snippet).


ADDING SNIPPETS                               *luasnip-basics-adding-snippets*

The snippets for a given filetype have to be added to luasnip via
`ls.add_snippets(filetype, snippets)`. Snippets that should be accessible
globally (in all filetypes) have to be added to the special filetype `all`.

>lua
    ls.add_snippets("all", {
        s("ternary", {
            -- equivalent to "${1:cond} ? ${2:then} : ${3:else}"
            i(1, "cond"), t(" ? "), i(2, "then"), t(" : "), i(3, "else")
        })
    })
<

It is possible to make snippets from one filetype available to another using
`ls.filetype_extend`, more info on that in the section |luasnip-api|.


SNIPPET INSERTION                           *luasnip-basics-snippet-insertion*

When a new snippet is expanded, it can be connected with the snippets that have
already been expanded in the buffer in various ways. First of all, Luasnip
distinguishes between root-snippets and child-snippets. The latter are nested
inside other snippets, so when jumping through a snippet, one may also traverse
the child-snippets expanded inside it, more or less as if the child just
contains more nodes of the parent. Root-snippets are of course characterised by
not being child-snippets. When expanding a new snippet, it becomes a child of
the snippet whose region it is expanded inside, and a root if it is not inside
any snippet’s region. If it is inside another snippet, the specific node it
is inside is determined, and the snippet then nested inside that node.

- If that node is interactive (for example, an `insertNode`), the new snippet
    will be traversed when the node is visited, as long as the
    configuration-option `link_children` is enabled. If it is not enabled, it is
    possible to jump from the snippet to the node, but not the other way around.
- If that node is not interactive, the snippet will be linked to the currently
    active node, also such that it will not be jumped to again once it is left.
    This is to prevent jumping large distances across the buffer as much as
    possible. There may still be one large jump from the snippet back to the
    current node it is nested inside, but that seems hard to avoid.
    Thus, one should design snippets such that the regions where other snippets
    may be expanded are inside `insertNodes`.

If the snippet is not a child, but a root, it can be linked up with the roots
immediately adjacent to it by enabling `link_roots` in `setup`. Since by
default only one root is remembered, one should also set `keep_roots` if
`link_roots` is enabled. The two are separate options, since roots that are not
linked can still be reached by `ls.activate_node()`. This setup (remember
roots, but don’t jump to them) is useful for a super-tab like mapping
(`<Tab>` and jump on the same key), where one would like to still enter
previous roots. Since there would almost always be more jumps if the roots are
linked, regular `<Tab>` would not work almost all the time, and thus
`link_roots` has to stay disabled.


==============================================================================
2. Node                                                         *luasnip-node*

Every node accepts, as its last parameter, an optional table of arguments.
There are some common ones (which are listed here), and some that only apply to
some nodes (`user_args` for function/dynamicNode). These `opts` are only
mentioned if they accept options that are not common to all nodes.

Common opts:

- `node_ext_opts` and `merge_node_ext_opts`: Control `ext_opts` (most likely
    highlighting) of the node. Described in detail in |luasnip-ext_opts|
- `key`: The node can be reffered to by this key. Useful for either |luasnip-key-indexer| or for finding the node at runtime (See
    |luasnip-snippets-api|), for example inside a `dynamicNode`. The keys
    do not have to be unique across the entire lifetime of the snippet, but at any
    point in time, the snippet may contain each key only once. This means it is
    fine to return a keyed node from a `dynamicNode`, because even if it will be
    generated multiple times, those will not be valid at the same time.
- `node_callbacks`: Define event-callbacks for this node (see
    |luasnip-events|).
    Accepts a table that maps an event, e.g. `events.enter` to the callback
    (essentially the same as `callbacks` passed to `s`, only that there is no
    first mapping from jump-index to the table of callbacks).


API                                                         *luasnip-node-api*

- `get_jump_index()`: this method returns the jump-index of a node. If a node
    doesn’t have a jump-index, this method returns `nil` instead.
- `get_buf_position(opts) -> {from_position, to_position}`:
    Determines the range of the buffer occupied by this node. `from`- and
    `to_position` are `row,column`-tuples, `0,0`-indexed (first line is 0, first
    column is 0) and end-inclusive (see |api-indexing|, this is extmarks
    indexing).
    - `opts`: `table|nil`, options, valid keys are:
        - `raw`: `bool`, default `true`. This can be used to switch between
            byte-columns (`raw=true`) and visual columns (`raw=false`). This makes a
            difference if the line contains characters represented by multiple bytes
            in UTF, for example `ÿ`.


==============================================================================
3. Snippets                                                 *luasnip-snippets*

The most direct way to define snippets is `s`:

>lua
    s({trig="trigger"}, {})
<

(This snippet is useless beyond serving as a minimal example)

`s(context, nodes, opts) -> snippet`

- `context`: Either table or a string. Passing a string is equivalent to passing
    >lua
        {
          trig = context
        }
    <
    The following keys are valid:
    - `trig`: string, the trigger of the snippet. If the text in front of (to the
        left of) the cursor when `ls.expand()` is called matches it, the snippet will
        be expanded. By default, "matches" means the text in front of the cursor
        matches the trigger exactly, this behaviour can be modified through
        `trigEngine`
    - `name`: string, can be used by e.g. `nvim-compe` to identify the snippet.
    - `desc` (or `dscr`): string, description of the snippet, -separated or table for
        multiple lines.
    - `wordTrig`: boolean, if true, the snippet is only expanded if the word
        (`[%w_]+`) before the cursor matches the trigger entirely. True by default.
    - `regTrig`: boolean, whether the trigger should be interpreted as a lua pattern.
        False by default. Consider setting `trigEngine` to `"pattern"` instead, it is
        more expressive, and in line with other settings.
    - `trigEngine`: (function|string), determines how `trig` is interpreted, and what
        it means for it to "match" the text in front of the cursor. This behaviour can
        be completely customized by passing a function, but the predefined ones, which
        are accessible by passing their identifier, should suffice in most cases:
        - `"plain"`: the default-behaviour, the trigger has to match the text before
            the cursor exactly.
        - `"pattern"`: the trigger is interpreted as a lua-pattern, and is a match if
            `trig .. "$"` matches the line up to the cursor. Capture-groups will be
            accessible as `snippet.captures`.
        - `"ecma"`: the trigger is interpreted as an ECMAscript-regex, and is a
            match if `trig .. "$"` matches the line up to the cursor. Capture-groups
            will be accessible as `snippet.captures`.
            This `trigEngine` requires `jsregexp` (see
            |luasnip-lsp-snippets-transformations|) to be installed, if it
            is not, this engine will behave like `"plain"`.
        - `"vim"`: the trigger is interpreted as a vim-regex, and is a match if
            `trig .. "$"` matches the line up to the cursor. As with the other
            regex/pattern-engines, captures will be available as `snippet.captures`,
            but there is one caveat: the matching is done using `matchlist`, so for
            now empty-string submatches will be interpreted as unmatched, and the
            corresponding `snippet.capture[i]` will be `nil` (this will most likely
            change, don’t rely on this behavior).
        Besides these predefined engines, it is also possible to create new ones:
        Instead of a string, pass a function which satisfies `trigEngine(trigger, opts)
        -> (matcher(line_to_cursor, trigger) -> whole_match, captures)` (ie. the
        function receives `trig` and `trigEngineOpts` can, for example, precompile a
        regex, and then returns a function responsible for determining whether the
        current cursor-position (represented by the line up to the cursor) matches the
        trigger (it is passed again here so engines which don’t do any
        trigger-specific work (like compilation) can just return a static `matcher`),
        and what the capture-groups are). The `lua`-engine, for example, can be
        implemented like this:
        >lua
            local function matcher(line_to_cursor, trigger)
                -- look for match which ends at the cursor.
                -- put all results into a list, there might be many capture-groups.
                local find_res = { line_to_cursor:find(trigger .. "$") }
            
                if #find_res > 0 then
                    -- if there is a match, determine matching string, and the
                    -- capture-groups.
                    local captures = {}
                    -- find_res[1] is `from`, find_res[2] is `to` (which we already know
                    -- anyway).
                    local from = find_res[1]
                    local match = line_to_cursor:sub(from, #line_to_cursor)
                    -- collect capture-groups.
                    for i = 3, #find_res do
                        captures[i - 2] = find_res[i]
                    end
                    return match, captures
                else
                    return nil
                end
            end
            
            local function engine(trigger)
                -- don't do any special work here, can't precompile lua-pattern.
                return matcher
            end
        <
        The predefined engines are defined in `trig_engines.lua`
        <https://github.com/L3MON4D3/LuaSnip/blob/master/lua/luasnip/nodes/util/trig_engines.lua>,
        read it for more examples.
    - `trigEngineOpts`: `table<string, any>`, options for the used trigEngine. The
        valid options are:
        - `max_len`: number, upper bound on the length of the trigger.
            If this is set, the `line_to_cursor` will be truncated (from the cursor of
            course) to `max_len` characters before performing the match.
            This is implemented because feeding long `line_to_cursor` into eg. the
            pattern-trigEngine will hurt performance quite a bit (see issue
            Luasnip#1103).
            This option is implemented for all `trigEngines`.
    - `docstring`: string, textual representation of the snippet, specified like
        `desc`. Overrides docstrings loaded from json.
    - `docTrig`: string, used as `line_to_cursor` during docstring-generation. This
        might be relevant if the snippet relies on specific values in the
        capture-groups (for example, numbers, which won’t work with the default
        `$CAPTURESN` used during docstring-generation)
    - `hidden`: boolean, hint for completion-engines. If set, the snippet should not
        show up when querying snippets.
    - `priority`: positive number, Priority of the snippet, 1000 by default. Snippets
        with high priority will be matched to a trigger before those with a lower one.
        The priority for multiple snippets can also be set in `add_snippets`.
    - `snippetType`: string, should be either `snippet` or `autosnippet` (ATTENTION:
        singular form is used), decides whether this snippet has to be triggered by
        `ls.expand()` or whether is triggered automatically (don’t forget to set
        `ls.config.setup({ enable_autosnippets = true })` if you want to use this
        feature). If unset it depends on how the snippet is added of which type the
        snippet will be.
    - `resolveExpandParams`: `fn(snippet, line_to_cursor, matched_trigger, captures)
        -> table|nil`, where
        - `snippet`: `Snippet`, the expanding snippet object
        - `line_to_cursor`: `string`, the line up to the cursor.
        - `matched_trigger`: `string`, the fully matched trigger (can be retrieved
            from `line_to_cursor`, but we already have that info here :D)
        - `captures`: `captures` as returned by `trigEngine`.
        This function will be evaluated in `Snippet:matches()` to decide whether the
        snippet can be expanded or not. Returns a table if the snippet can be expanded,
        `nil` if can not. The returned table can contain any of these fields:
        - `trigger`: `string`, the fully matched trigger.
        - `captures`: `table`, this list could update the capture-groups from
            parameter in snippet expansion.
            Both `trigger` and `captures` can override the values returned via
            `trigEngine`.
        - `clear_region`: `{ "from": {<row>, <column>}, "to": {<row>, <column>} }`,
            both (0, 0)-indexed, the region where text has to be cleared before
            inserting the snippet.
        - `env_override`: `map string->(string[]|string)`, override or extend
            the snippet’s environment (`snip.env`)
        If any of these is `nil`, the default is used (`trigger` and `captures` as
        returned by `trigEngine`, `clear_region` such that exactly the trigger is
        deleted, no overridden environment-variables).
        A good example for the usage of `resolveExpandParams` can be found in the
        implementation of `postfix`
        <https://github.com/L3MON4D3/LuaSnip/blob/master/lua/luasnip/extras/postfix.lua>.
    - `condition`: `fn(line_to_cursor, matched_trigger, captures) -> bool`, where
        - `line_to_cursor`: `string`, the line up to the cursor.
        - `matched_trigger`: `string`, the fully matched trigger (can be retrieved
            from `line_to_cursor`, but we already have that info here :D)
        - `captures`: if the trigger is pattern, this list contains the
            capture-groups. Again, could be computed from `line_to_cursor`, but we
            already did so.
    - `show_condition`: `f(line_to_cursor) -> bool`.
        - `line_to_cursor`: `string`, the line up to the cursor.
        This function is (should be) evaluated by completion engines, indicating
        whether the snippet should be included in current completion candidates.
        Defaults to a function returning `true`. This is different from `condition`
        because `condition` is evaluated by LuaSnip on snippet expansion (and thus has
        access to the matched trigger and captures), while `show_condition` is (should
        be) evaluated by the completion engines when scanning for available snippet
        candidates.
    - `filetype`: `string`, the filetype of the snippet. This overrides the filetype
        the snippet is added (via `add_snippet`) as.
- `nodes`: A single node or a list of nodes. The nodes that make up the snippet.
- `opts`: A table with the following valid keys:
    - `callbacks`: Contains functions that are called upon entering/leaving a node of
        this snippet. For example: to print text upon entering the _second_ node of a
        snippet, `callbacks` should be set as follows:
        >lua
            {
                -- position of the node, not the jump-index!!
                -- s("trig", {t"first node", t"second node", i(1, "third node")}).
                [2] = {
                    [events.enter] = function(node, _event_args) print("2!") end
                }
            }
        <
        To register a callback for the snippets’ own events, the key `[-1]` may be
        used. More info on events in |luasnip-events|
    - `child_ext_opts`, `merge_child_ext_opts`: Control `ext_opts` applied to the
        children of this snippet. More info on those in the |luasnip-ext_opts|-section.

The `opts`-table, as described here, can also be passed to e.g. `snippetNode`
and `indentSnippetNode`. It is also possible to set `condition` and
`show_condition` (described in the documentation of the `context`-table) from
`opts`. They should, however, not be set from both.


DATA                                                   *luasnip-snippets-data*

Snippets contain some interesting tables during runtime:

- `snippet.env`: Contains variables used in the LSP-protocol, for example
    `TM_CURRENT_LINE` or `TM_FILENAME`. It’s possible to add customized variables
    here too, check |luasnip-variables-environment-namespaces|
- `snippet.captures`: If the snippet was triggered by a pattern (`regTrig`), and
    the pattern contained capture-groups, they can be retrieved here.
- `snippet.trigger`: The string that triggered this snippet. Again, only
    interesting if the snippet was triggered through `regTrig`, for getting the
    full match.

These variables/tables primarily come in handy in `dynamic/functionNodes`,
where the snippet can be accessed through the immediate parent
(`parent.snippet`), which is passed to the function. (in most cases `parent ==
parent.snippet`, but the `parent` of the dynamicNode is not always the
surrounding snippet, it could be a `snippetNode`).

## Api

- `invalidate()`: call this method to effectively remove the snippet. The
    snippet will no longer be able to expand via `expand` or `expand_auto`. It
    will also be hidden from lists (at least if the plugin creating the list
    respects the `hidden`-key), but it might be necessary to call
    `ls.refresh_notify(ft)` after invalidating snippets.
- `get_keyed_node(key)`: Returns the currently visible node associated with
    `key`.


==============================================================================
4. TextNode                                                 *luasnip-textnode*

The most simple kind of node; just text.

>lua
    s("trigger", { t("Wow! Text!") })
<

This snippet expands to

>
        Wow! Text!⎵
<

where ⎵ is the cursor.

Multiline strings can be defined by passing a table of lines rather than a
string:

>lua
    s("trigger", {
        t({"Wow! Text!", "And another line."})
    })
<

`t(text, node_opts)`:

- `text`: `string` or `string[]`
- `node_opts`: `table`, see |luasnip-node|


==============================================================================
5. InsertNode                                             *luasnip-insertnode*

These Nodes contain editable text and can be jumped to- and from (e.g.
traditional placeholders and tabstops, like `$1` in textmate-snippets).

The functionality is best demonstrated with an example:

>lua
    s("trigger", {
        t({"After expanding, the cursor is here ->"}), i(1),
        t({"", "After jumping forward once, cursor is here ->"}), i(2),
        t({"", "After jumping once more, the snippet is exited there ->"}), i(0),
    })
<

The Insert Nodes are visited in order `1,2,3,..,n,0`. (The jump-index 0 also
_has_ to belong to an `insertNode`!) So the order of InsertNode-jumps is as
follows:

1. After expansion, the cursor is at InsertNode 1,
2. after jumping forward once at InsertNode 2,
3. and after jumping forward again at InsertNode 0.

If no 0-th InsertNode is found in a snippet, one is automatically inserted
after all other nodes.

The jump-order doesn’t have to follow the "textual" order of the nodes:

>lua
    s("trigger", {
        t({"After jumping forward once, cursor is here ->"}), i(2),
        t({"", "After expanding, the cursor is here ->"}), i(1),
        t({"", "After jumping once more, the snippet is exited there ->"}), i(0),
    })
<

The above snippet will behave as follows:

1. After expansion, we will be at InsertNode 1.
2. After jumping forward, we will be at InsertNode 2.
3. After jumping forward again, we will be at InsertNode 0.

An **important** (because here Luasnip differs from other snippet engines)
detail is that the jump-indices restart at 1 in nested snippets:

>lua
    s("trigger", {
        i(1, "First jump"),
        t(" :: "),
        sn(2, {
            i(1, "Second jump"),
            t" : ",
            i(2, "Third jump")
        })
    })
<

as opposed to e.g. the textmate syntax, where tabstops are snippet-global:

>snippet
    ${1:First jump} :: ${2: ${3:Third jump} : ${4:Fourth jump}}
<

(this is not exactly the same snippet of course, but as close as possible) (the
restart-rule only applies when defining snippets in lua, the above
textmate-snippet will expand correctly when parsed).

`i(jump_index, text, node_opts)`

- `jump_index`: `number`, this determines when this node will be jumped to (see
    |luasnip-basics-jump-index|).
- `text`: `string|string[]`, a single string for just one line, a list with >1
    entries for multiple lines.
    This text will be SELECTed when the `insertNode` is jumped into.
- `node_opts`: `table`, described in |luasnip-node|

If the `jump_index` is `0`, replacing its’ `text` will leave it outside the
`insertNode` (for reasons, check out Luasnip#110).


==============================================================================
6. FunctionNode                                         *luasnip-functionnode*

Function Nodes insert text based on the content of other nodes using a
user-defined function:

>lua
    local function fn(
      args,     -- text from i(2) in this example i.e. { { "456" } }
      parent,   -- parent snippet or parent node
      user_args -- user_args from opts.user_args 
    )
       return '[' .. args[1][1] .. user_args .. ']'
    end
    
    s("trig", {
      i(1), t '<-i(1) ',
      f(fn,  -- callback (args, parent, user_args) -> string
        {2}, -- node indice(s) whose text is passed to fn, i.e. i(2)
        { user_args = { "user_args_value" }} -- opts
      ),
      t ' i(2)->', i(2), t '<-i(2) i(0)->', i(0)
    })
<

`f(fn, argnode_references, node_opts)`: - `fn`: `function(argnode_text, parent,
user_args1,...,user_argsn) -> text` - `argnode_text`: `string[][]`, the text
currently contained in the argnodes (e.g. `{{line1}, {line1, line2}}`). The
snippet indent will be removed from all lines following the first.

- `parent`: The immediate parent of the `functionNode`. It is included here as it
    allows easy access to some information that could be useful in functionNodes
    (see |luasnip-snippets-data| for some examples). Many snippets access the
    surrounding snippet just as `parent`, but if the `functionNode` is nested
    within a `snippetNode`, the immediate parent is a `snippetNode`, not the
    surrounding snippet (only the surrounding snippet contains data like `env` or
    `captures`).
- `user_args`: The `user_args` passed in `opts`. Note that there may be multiple
    user_args (e.g. `user_args1, ..., user_argsn`).

`fn` shall return a string, which will be inserted as is, or a table of strings
for multiline strings, where all lines following the first will be prefixed
with the snippets’ indentation.

- `argnode_references`: `node_reference[]|node_refernce|nil`. Either no, a
    single, or multiple |luasnip-node-reference|s. Changing any of these will
    trigger a re-evaluation of `fn`, and insertion of the updated text. If no node
    reference is passed, the `functionNode` is evaluated once upon expansion.
- `node_opts`: `table`, see |luasnip-node|. One additional key is supported:
    - `user_args`: `any[]`, these will be passed to `fn` as `user_arg1`-`user_argn`.
        These make it easier to reuse similar functions, for example a functionNode
        that wraps some text in different delimiters (`()`, `[]`, …).
        >lua
            local function reused_func(_,_, user_arg1)
                return user_arg1
            end
            
            s("trig", {
                f(reused_func, {}, {
                    user_args = {"text"}
                }),
                f(reused_func, {}, {
                    user_args = {"different text"}
                }),
            })
        <

**Examples**:

- Use captures from the regex trigger using a functionNode:
    >lua
        s({trig = "b(%d)", regTrig = true},
          f(function(args, snip) return
              "Captured Text: " .. snip.captures[1] .. "." end, {})
        )
    <
- `argnodes_text` during function evaluation:
    >lua
        s("trig", {
          i(1, "text_of_first"),
          i(2, {"first_line_of_second", "second_line_of_second"}),
          f(function(args, snip)
              --here
          -- order is 2,1, not 1,2!!
          end, {2, 1} )})
    <
    At `--here`, `args` would look as follows (provided no text was changed after
    expansion):
    >lua
        args = {
          {"first_line_of_second", "second_line_of_second"},
          {"text_of_first"}
        }
    <
- |luasnip-absolute-indexer|:
    >lua
        s("trig", {
          i(1, "text_of_first"),
          i(2, {"first_line_of_second", "second_line_of_second"}),
          f(function(args, snip)
              -- just concat first lines of both.
              return args[1][1] .. args[2][1]
          end, {ai[2], ai[1]} )})
    <

If the function only performs simple operations on text, consider using the
`lambda` from `luasnip.extras` (See |luasnip-extras-lambda|)


==============================================================================
7. Node Reference                                     *luasnip-node-reference*

Node references are used to refer to other nodes in various parts of
luasnip’s API. For example, argnodes in functionNode, dynamicNode or lambda
are node references. These references can be either of:

- `number`: the jump-index of the node.
    This will be resolved relative to the parent of the node this is passed to.
    (So, only nodes with the same parent can be referenced. This is very easy to
    grasp, but also limiting)
- `key_indexer`: the key of the node, if it is present. This will come in
    handy if the node that is being referred to is not in the same
    snippet/snippetNode as the one the node reference is passed to.
    Also, it is the proper way to refer to a non-interactive node (a
    functionNode, for example)
- `absolute_indexer`: the absolute position of the node. Just like
    `key_indexer`, it allows addressing non-sibling nodes, but is a bit more
    awkward to handle since a path from root to node has to be determined,
    whereas `key_indexer` just needs the key to match.
    Due to this, `key_indexer` should be generally preferred.
    (More information in |luasnip-absolute-indexer|).
- `node`: just the node. Usage of this is discouraged since it can lead to
    subtle errors (for example, if the node passed here is captured in a closure
    and therefore not copied with the remaining tables in the snippet; there’s a
    big comment about just this in commit 8bfbd61).


==============================================================================
8. ChoiceNode                                             *luasnip-choicenode*

ChoiceNodes allow choosing between multiple nodes.

>lua
     s("trig", c(1, {
        t("Ugh boring, a text node"),
        i(nil, "At least I can edit something now..."),
        f(function(args) return "Still only counts as text!!" end, {})
     }))
<

`c(jump_index, choices, node_opts)`

- `jump_index`: `number`, since choiceNodes can be jumped to, they need a
    jump-index (Info in |luasnip-basics-jump-index|).
- `choices`: `node[]|node`, the choices. The first will be initialliy active.
    A list of nodes will be turned into a `snippetNode`.
- `node_opts`: `table`. `choiceNode` supports the keys common to all nodes
    described in |luasnip-node|, and one additional key:
    - `restore_cursor`: `false` by default. If it is set, and the node that was being
        edited also appears in the switched to choice (can be the case if a
        `restoreNode` is present in both choice) the cursor is restored relative to
        that node. The default is `false` as enabling might lead to decreased
        performance. It’s possible to override the default by wrapping the
        `choiceNode` constructor in another function that sets `opts.restore_cursor` to
        `true` and then using that to construct `choiceNode`s:
        >lua
            local function restore_cursor_choice(pos, choices, opts)
                if opts then
                    opts.restore_cursor = true
                else
                    opts = {restore_cursor = true}
                end
                return c(pos, choices, opts)
            end
        <

Jumpable nodes that normally expect an index as their first parameter don’t
need one inside a choiceNode; their jump-index is the same as the
choiceNodes’.

As it is only possible (for now) to change choices from within the choiceNode,
make sure that all of the choices have some place for the cursor to stop at!

This means that in `sn(nil, {...nodes...})` `nodes` has to contain e.g. an
`i(1)`, otherwise luasnip will just "jump through" the nodes, making it
impossible to change the choice.

>lua
    c(1, {
        t"some text", -- textNodes are just stopped at.
        i(nil, "some text"), -- likewise.
        sn(nil, {t"some text"}) -- this will not work!
        sn(nil, {i(1), t"some text"}) -- this will.
    })
<

The active choice for a choiceNode can be changed by either calling one of
`ls.change_choice(1)` (forwards) or `ls.change_choice(-1)` (backwards), or by
calling `ls.set_choice(choice_indx)`.

One way to easily interact with choiceNodes is binding `change_choice(1/-1)` to
keys:

>lua
    -- set keybinds for both INSERT and VISUAL.
    vim.api.nvim_set_keymap("i", "<C-n>", "<Plug>luasnip-next-choice", {})
    vim.api.nvim_set_keymap("s", "<C-n>", "<Plug>luasnip-next-choice", {})
    vim.api.nvim_set_keymap("i", "<C-p>", "<Plug>luasnip-prev-choice", {})
    vim.api.nvim_set_keymap("s", "<C-p>", "<Plug>luasnip-prev-choice", {})
<

Apart from this, there is also a picker (see |luasnip-select_choice| where no
cycling is necessary and any choice can be selected right away, via
`vim.ui.select`.


==============================================================================
9. SnippetNode                                           *luasnip-snippetnode*

SnippetNodes directly insert their contents into the surrounding snippet. This
is useful for `choiceNode`s, which only accept one child, or `dynamicNode`s,
where nodes are created at runtime and inserted as a `snippetNode`.

Their syntax is similar to `s`, however, where snippets require a table
specifying when to expand, `snippetNode`s, similar to `insertNode`s, expect a
jump-index.

>lua
     s("trig", sn(1, {
        t("basically just text "),
        i(1, "And an insertNode.")
     }))
<

`sn(jump_index, nodes, node_opts)`

- `jump_index`: `number`, the usual |luasnip-jump-index|.
- `nodes`: `node[]|node`, just like for `s`.
    Note that `snippetNode`s don’t accept an `i(0)`, so the jump-indices of the nodes
    inside them have to be in `1,2,...,n`.
- `node_opts`: `table`: again, the keys common to all nodes (documented in
    |luasnip-node|) are supported, but also
    - `callbacks`,
    - `child_ext_opts` and
    - `merge_child_ext_opts`,
    which are further explained in |luasnip-snippets|.


==============================================================================
10. IndentSnippetNode                              *luasnip-indentsnippetnode*

By default, all nodes are indented at least as deep as the trigger. With these
nodes it’s possible to override that behaviour:

>lua
    s("isn", {
        isn(1, {
            t({"This is indented as deep as the trigger",
            "and this is at the beginning of the next line"})
        }, "")
    })
<

(Note the empty string passed to isn).

Indent is only applied after linebreaks, so it’s not possible to remove
indent on the line where the snippet was triggered using `ISN` (That is
possible via regex triggers where the entire line before the trigger is
matched).

Another nice use case for `ISN` is inserting text, e.g. `//` or some other
comment string before the nodes of the snippet:

>lua
    s("isn2", {
        isn(1, t({"//This is", "A multiline", "comment"}), "$PARENT_INDENT//")
    })
<

Here the `//` before `This is` is important, once again, because indent is only
applied after linebreaks.

To enable such usage, `$PARENT_INDENT` in the indentstring is replaced by the
parent’s indent.

`isn(jump_index, nodes, indentstring, node_opts)`

All of these parameters except `indentstring` are exactly the same as in
|luasnip-snippetnode|.

- `indentstring`: `string`, will be used to indent the nodes inside this
    `snippetNode`.
    All occurences of `"$PARENT_INDENT"` are replaced with the actual indent of
    the parent.


==============================================================================
11. DynamicNode                                          *luasnip-dynamicnode*

Very similar to functionNode, but returns a snippetNode instead of just text,
which makes them very powerful as parts of the snippet can be changed based on
user input.

`d(jump_index, function, node-references, opts)`:

- `jump_index`: `number`, just like all jumpable nodes, its’ position in the
    jump-list (|luasnip-basics-jump-index|).
- `function`: `fn(args, parent, old_state, user_args) -> snippetNode` This
    function is called when the argnodes’ text changes. It should generate and
    return (wrapped inside a `snippetNode`) nodes, which will be inserted at the
    dynamicNode’s place. `args`, `parent` and `user_args` are also explained in
    |luasnip-functionnode|
    - `args`: `table of text` (`{{"node1line1", "node1line2"}, {"node2line1"}}`)
        from nodes the `dynamicNode` depends on.
    - `parent`: the immediate parent of the `dynamicNode`.
    - `old_state`: a user-defined table. This table may contain anything; its
        intended usage is to preserve information from the previously generated
        `snippetNode`. If the `dynamicNode` depends on other nodes, it may be
        reconstructed, which means all user input (text inserted in `insertNodes`,
        changed choices) to the previous `dynamicNode` is lost.
        The `old_state` table must be stored in `snippetNode` returned by
        the function (`snippetNode.old_state`).
        The second example below illustrates the usage of `old_state`.
    - `user_args`: passed through from `dynamicNode`-opts; may have more than one
        argument.
- `node_references`: `node_reference[]|node_references|nil`,
    |luasnip-node-references| to the nodes the dynamicNode depends on: if any of
    these trigger an update (for example, if the text inside them changes), the
    `dynamicNode`s’ function will be executed, and the result inserted at the
    `dynamicNode`s place. (`dynamicNode` behaves exactly the same as `functionNode`
    in this regard).
- `opts`: In addition to the common |luasnip-node|-keys, there is, again,
    - `user_args`, which is described in |luasnip-functionnode|.

**Examples**:

This `dynamicNode` inserts an `insertNode` which copies the text inside the
first `insertNode`.

>lua
    s("trig", {
        t"text: ", i(1), t{"", "copy: "},
        d(2, function(args)
                -- the returned snippetNode doesn't need a position; it's inserted
                -- "inside" the dynamicNode.
                return sn(nil, {
                    -- jump-indices are local to each snippetNode, so restart at 1.
                    i(1, args[1])
                })
            end,
        {1})
    })
<

This snippet makes use of `old_state` to count the number of updates.

To store/restore values generated by the `dynamicNode` or entered into
`insert/choiceNode`, consider using the shortly-introduced `restoreNode`
instead of `old_state`.

>lua
    local function count(_, _, old_state)
        old_state = old_state or {
            updates = 0
        }
    
        old_state.updates = old_state.updates + 1
    
        local snip = sn(nil, {
            t(tostring(old_state.updates))
        })
    
        snip.old_state = old_state
        return snip
    end
    
    ls.add_snippets("all",
        s("trig", {
            i(1, "change to update"),
            d(2, count, {1})
        })
    )
<

As with `functionNode`, `user_args` can be used to reuse similar `dynamicNode`-
functions.


==============================================================================
12. RestoreNode                                          *luasnip-restorenode*

This node can store and restore a snippetNode as is. This includes changed
choices and changed text. Its’ usage is best demonstrated by an example:

>lua
    s("paren_change", {
        c(1, {
            sn(nil, { t("("), r(1, "user_text"), t(")") }),
            sn(nil, { t("["), r(1, "user_text"), t("]") }),
            sn(nil, { t("{"), r(1, "user_text"), t("}") }),
        }),
    }, {
        stored = {
            -- key passed to restoreNodes.
            ["user_text"] = i(1, "default_text")
        }
    })
<

Here the text entered into `user_text` is preserved upon changing choice.

`r(jump_index, key, nodes, node_opts)`:

- `jump_index`, when to jump to this node.
- `key`, `string`: `restoreNode`s with the same key share their content.
- `nodes`, `node[]|node`: the content of the `restoreNode`.
    Can either be a single node, or a table of nodes (both of which will be
    wrapped inside a `snippetNode`, except if the single node already is a
    `snippetNode`).
    The content for a given key may be defined multiple times, but if the
    contents differ, it’s undefined which will actually be used.
    If a key’s content is defined in a `dynamicNode`, it will not be initially
    used for `restoreNodes` outside that `dynamicNode`. A way around this
    limitation is defining the content in the `restoreNode` outside the
    `dynamicNode`.

The content for a key may also be defined in the `opts`-parameter of the
snippet-constructor, as seen in the example above. The `stored`-table accepts
the same values as the `nodes`-parameter passed to `r`. If no content is
defined for a key, it defaults to the empty `insertNode`.

An important-to-know limitation of `restoreNode` is that, for a given key, only
one may be visible at a time. See this issue
<https://github.com/L3MON4D3/LuaSnip/issues/234> for details.

The `restoreNode` is especially useful for storing input across updates of a
`dynamicNode`. Consider this:

>lua
    local function simple_restore(args, _)
        return sn(nil, {i(1, args[1]), i(2, "user_text")})
    end
    
    s("rest", {
        i(1, "preset"), t{"",""},
        d(2, simple_restore, 1)
    })
<

Every time the `i(1)` in the outer snippet is changed, the text inside the
`dynamicNode` is reset to `"user_text"`. This can be prevented by using a
`restoreNode`:

>lua
    local function simple_restore(args, _)
        return sn(nil, {i(1, args[1]), r(2, "dyn", i(nil, "user_text"))})
    end
    
    s("rest", {
        i(1, "preset"), t{"",""},
        d(2, simple_restore, 1)
    })
<

Now the entered text is stored.

`restoreNode`s indent is not influenced by `indentSnippetNodes` right now. If
that really bothers you feel free to open an issue.


==============================================================================
13. Key Indexer                                          *luasnip-key-indexer*

A very flexible way of referencing nodes (|luasnip-node-reference|). While the
straightforward way of addressing nodes via their |luasnip-jump-index| suffices
in most cases, a `dynamic/functionNode` can only depend on nodes in the same
snippet(Node), its siblings (since the index is interpreted as relative to
their parent). Accessing a node with a different parent is thus not possible.
Secondly, and less relevant, only nodes that actually have a jump-index can be
referred to (a `functionNode`, for example, cannot be depended on). Both of
these restrictions are lifted with `key_indexer`: It allows addressing nodes by
their key, which can be set when the node is constructed, and is wholly
independent of the nodes’ position in the snippet, thus enabling descriptive
labeling.

The following snippets demonstrate the issue and the solution by using
`key_indexer`:

First, the addressed problem of referring to nodes outside the `functionNode`s
parent:

>lua
    s("trig", {
        i(1), c(2, {
            sn(nil, {
                t"cannot access the argnode :(",
                f(function(args)
                    return args[1]
                end, {???}) -- can't refer to i(1), since it isn't a sibling of `f`.
            }),
            t"sample_text"
        })
    })
<

And the solution: first give the node we want to refer to a key, and then pass
the same to the `functionNode`.

>lua
    s("trig", {
        i(1, "", {key = "i1-key"}), c(2, {
            sn(nil, { i(1),
                t"can access the argnode :)",
                f(function(args)
                    return args[1]
                end, k("i1-key") )
            }),
            t"sample_text"
        })
    })
<


==============================================================================
14. Absolute Indexer                                *luasnip-absolute-indexer*

`absolute_indexer` allows accessing nodes by their unique jump-index path from
the snippet-root. This makes it almost as powerful as |luasnip-key-indexer|,
but again removes the possibility of referring to non-jumpable nodes and makes
it all a bit more error-prone since the jump-index paths are hard to follow,
and (unfortunately) have to be a bit verbose (see the long example of
`absolute_indexer`-positions below). Consider just using |luasnip-key-indexer|
instead.

(The solution-snippet from |luasnip-key-indexer|, but using `ai` instead.)

>lua
    s("trig", {
        i(1), c(2, {
            sn(nil, { i(1),
                t"can access the argnode :)",
                f(function(args)
                    return args[1]
                end, ai(1) )
            }),
            t"sample_text"
        })
    })
<

There are some quirks in addressing nodes:

>lua
    s("trig", {
        i(2), -- ai[2]: indices based on jump-index, not position.
        sn(1, { -- ai[1]
            i(1), -- ai[1][1]
            t"lel", -- not addressable.
            i(2) -- ai[1][2]
        }),
        c(3, { -- ai[3]
            i(nil), -- ai[3][1]
            t"lel", -- ai[3][2]: choices are always addressable.
        }),
        d(4, function() -- ai[4]
            return sn(nil, { -- ai[4][0]
                i(1), -- ai[4][0][1]
            })
        end, {}),
        r(5, "restore_key", -- ai[5]
            i(1) -- ai[5][0][1]: restoreNodes always store snippetNodes.
        ),
        r(6, "restore_key_2", -- ai[6]
            sn(nil, { -- ai[6][0]
                i(1) -- ai[6][0][1]
            })
        )
    })
<

Note specifically that the index of a dynamicNode differs from that of the
generated snippetNode, and that restoreNodes (internally) always store a
snippetNode, so even if the restoreNode only contains one node, that node has
to be accessed as `ai[restoreNodeIndx][0][1]`.

`absolute_indexer`s’ can be constructed in different ways:

- `ai[1][2][3]`
- `ai(1, 2, 3)`
- `ai{1, 2, 3}`

are all the same node.


==============================================================================
15. MultiSnippet                                        *luasnip-multisnippet*

There are situations where it might be comfortable to access a snippet in
different ways. For example, one might want to enable auto-triggering in
regions where the snippets usage is common, while leaving it manual-only in
others. This is where `ms` should be used: A single snippet can be associated
with multiple `context`s (the `context`-table determines the conditions under
which a snippet may be triggered). This has the advantage (compared with just
registering copies) that all `context`s are backed by a single snippet, and not
multiple, and it’s (at least should be :D) more comfortable to use.

`ms(contexts, nodes, opts) -> addable`:

- `contexts`: table containing list of `contexts`, and some keywords.
    `context` are described in |luasnip-snippets|, here they may also be tables
    or strings.
    So far, there is only one valid keyword:
    - `common`: Accepts yet another context.
        The options in `common` are applied to (but don’t override) the other
        contexts specified in `contexts`.
- `nodes`: List of nodes, exactly like in |luasnip-snippets|.
- `opts`: Table, options for this function:
    - `common_opts`: The snippet-options (see also |luasnip-snippets|) applied
        to the snippet generated from `nodes`.

The returned object is an `addable`, something which can be passed to
`add_snippets`, or returned from the lua-loader.

**Examples**:

>lua
    ls.add_snippets("all", {
        ms({"a", "b"}, {t"a or b"})
    })
<

>lua
    ls.add_snippets("all", {
        ms({
            common = {snippetType = "autosnippet"},
            "a",
            "b"
        }, {
            t"a or b (but autotriggered!!)"
        })
    })
<

>lua
    ls.add_snippets("all", {
        ms({
            common = {snippetType = "autosnippet"},
            {trig = "a", snippetType = "snippet"},
            "b",
            {trig = "c", condition = function(line_to_cursor)
                return line_to_cursor == ""
            end}
        }, {
            t"a or b (but autotriggered!!)"
        })
    })
<


==============================================================================
16. Extras                                                    *luasnip-extras*


LAMBDA                                                 *luasnip-extras-lambda*

A shortcut for `functionNode`s that only do very basic string manipulation.

`l(lambda, argnodes)`:

- `lambda`: An object created by applying string-operations to `l._n`, objects
    representing the `n`th argnode.
    For example:
    - `l._1:gsub("a", "e")` replaces all occurences of "a" in the text of the
        first argnode with "e", or
    - `l._1 .. l._2` concatenates text of the first and second argnode.
        If an argnode contains multiple lines of text, they are concatenated with
        `"\n"` prior to any operation.
- `argnodes`, a |luasnip-node-reference|, just like in function- and
    dynamicNode.

There are many examples for `lambda` in `Examples/snippets.lua`


MATCH                                                   *luasnip-extras-match*

`match` can insert text based on a predicate (again, a shorthand for
`functionNode`).

`match(argnodes, condition, then, else)`:

- `argnode`: A single |luasnip-node-reference|. May not be nil, or
    a table.
- `condition` may be either of
    - `string`: interpreted as a lua pattern. Matched on the `\n`-joined (in case
        it’s multiline) text of the first argnode (`args[1]:match(condition)`).
    - `function`: `fn(args, snip) -> bool`: takes the same parameters as the
        `functionNode`-function, any value other than nil or false is interpreted
        as a match.
    - `lambda`: `l._n` is the `\n`-joined text of the nth argnode.
        Useful if string manipulations have to be performed before the string is matched.
        Should end with `match`, but any other truthy result will be interpreted
        as matching.
- `then` is inserted if the condition matches,
- `else` if it does not.

Both `then` and `else` can be either text, lambda or function (with the same
parameters as specified above). `then`’s default-value depends on the
`condition`:

- `pattern`: Simply the return value from the `match`, e.g. the entire match,
    or, if there were capture groups, the first capture group.
- `function`: the return value of the function if it is either a string, or a
    table (if there is no `then`, the function cannot return a table containing
    something other than strings).
- `lambda`: Simply the first value returned by the lambda.

Examples:

- `match(n, "^ABC$", "A")`.
- `match(n, lambda._1:match(lambda._1:reverse()), "PALINDROME")`
    >lua
        s("trig", {
          i(1), t":",
          i(2), t"::",
          m({1, 2}, l._1:match("^"..l._2.."$"), l._1:gsub("a", "e"))
        })
    <
- >lua
            s("extras1", {
              i(1), t { "", "" }, m(1, "^ABC$", "A")
            })
    <
    Inserts "A" if the node with jump-index `n` matches "ABC" exactly, nothing
    otherwise.
- >lua
          s("extras2", {
            i(1, "INPUT"), t { "", "" }, m(1, l._1:match(l._1:reverse()), "PALINDROME")
          })
    <
    Inserts `"PALINDROME"` if i(1) contains a palindrome.
- >lua
          s("extras3", {
            i(1), t { "", "" }, i(2), t { "", "" },
            m({ 1, 2 }, l._1:match("^" .. l._2 .. "$"), l._1:gsub("a", "e"))
          })
    <
    This inserts the text of the node with jump-index 1, with all occurences of `a`
    replaced with `e`, if the second insertNode matches the first exactly.


REPEAT                                                 *luasnip-extras-repeat*

Inserts the text of the passed node.

`rep(node_reference)` - `node_reference`, a single |luasnip-node-reference|.

>lua
    s("extras4", { i(1), t { "", "" }, extras.rep(1) })
<


PARTIAL                                               *luasnip-extras-partial*

Evaluates a function on expand and inserts its value.

`partial(fn, params...)` - `fn`: any function - `params`: varargs, any, will be
passed to `fn`.

For example `partial(os.date, "%Y")` inserts the current year on expansion.

>lua
    s("extras5", { extras.partial(os.date, "%Y") })
<


NONEMPTY                                             *luasnip-extras-nonempty*

Inserts text if the referenced node doesn’t contain any text.

`nonempty(node_reference, not_empty, empty)`:

- `node_reference`, a single |luasnip-node-reference|.
- `not_empty`, `string`: inserted if the node is not empty.
- `empty`, `string`: inserted if the node is empty.

>lua
    s("extras6", { i(1, ""), t { "", "" }, extras.nonempty(1, "not empty!", "empty!") })
<


DYNAMIC LAMBDA                                 *luasnip-extras-dynamic-lambda*

Pretty much the same as lambda, but it inserts the resulting text as an
insertNode, and, as such, it can be quickly overridden.

`dynamic_lambda(jump_indx, lambda, node_references)` - `jump_indx`, as usual,
the jump-indx.

The remaining arguments carry over from lambda.

>lua
    s("extras7", { i(1), t { "", "" }, extras.dynamic_lambda(2, l._1 .. l._1, 1) })
<


FMT                                                       *luasnip-extras-fmt*

Authoring snippets can be quite clunky, especially since every second node is
probably a `textNode`, inserting a small number of characters between two more
complicated nodes.

`fmt` can be used to define snippets in a much more readable way. This is
achieved by borrowing (as the name implies) from `format`-functionality (our
syntax is very similar to python’s
<https://docs.python.org/3/library/stdtypes.html#str.format>).

`fmt` accepts a string and a table of nodes. Each occurrence of a delimiter
pair in the string is replaced by one node from the table, while text outside
the delimiters is turned into textNodes.

Simple example:

>lua
    ls.add_snippets("all", {
      -- important! fmt does not return a snippet, it returns a table of nodes.
      s("example1", fmt("just an {iNode1}", {
        iNode1 = i(1, "example")
      })),
      s("example2", fmt([[
      if {} then
        {}
      end
      ]], {
        -- i(1) is at nodes[1], i(2) at nodes[2].
        i(1, "not now"), i(2, "when")
      })),
      s("example3", fmt([[
      if <> then
        <>
      end
      ]], {
        -- i(1) is at nodes[1], i(2) at nodes[2].
        i(1, "not now"), i(2, "when")
      }, {
        delimiters = "<>"
      })),
      s("example4", fmt([[
      repeat {a} with the same key {a}
      ]], {
        a = i(1, "this will be repeat")
      }, {
        repeat_duplicates = true
      }))
    })
<

One important detail here is that the position of the delimiters does not, in
any way, correspond to the jump-index of the nodes!

`fmt(format:string, nodes:table of nodes, opts:table|nil) -> table of nodes`

- `format`: a string. Occurences of `{<somekey>}` ( `{}` are customizable; more
    on that later) are replaced with `content[<somekey>]` (which should be a
    node), while surrounding text becomes `textNode`s.
    To escape a delimiter, repeat it (`"{{"`).
    If no key is given (`{}`) are numbered automatically:
    `"{} ? {} : {}"` becomes `"{1} ? {2} : {3}"`, while
    `"{} ? {3} : {}"` becomes `"{1} ? {3} : {4}"` (the count restarts at each
    numbered placeholder).
    If a key appears more than once in `format`, the node in
    `content[<duplicate_key>]` is inserted for the first, and copies of it for
    subsequent occurences.
- `nodes`: just a table of nodes.
- `opts`: optional arguments:
    - `delimiters`: string, two characters. Change `{}` to some other pair, e.g.
        `"<>"`.
    - `strict`: Warn about unused nodes (default true).
    - `trim_empty`: remove empty (`"%s*"`) first and last line in `format`. Useful
        when passing multiline strings via `[[]]` (default true).
    - `dedent`: remove indent common to all lines in `format`. Again, makes
        passing multiline-strings a bit nicer (default true).
    - `repeat_duplicates`: repeat nodes when a key is reused instead of copying
        the node if it has a jump-index, refer to |luasnip-basics-jump-index| to
        know which nodes have a jump-index (default false).

There is also `require("luasnip.extras.fmt").fmta`. This only differs from
`fmt` by using angle brackets (`<>`) as the default delimiter.


CONDITIONS                                         *luasnip-extras-conditions*

This module (`luasnip.extras.condition`) contains functions that can be passed
to a snippet’s `condition` or `show_condition`. These are grouped accordingly
into `luasnip.extras.conditions.expand` and `luasnip.extras.conditions.show`:

**expand**:

- `line_begin`: only expand if the cursor is at the beginning of the line.

**show**:

- `line_end`: only expand at the end of the line.
- `has_selected_text`: only expand if there’s selected text stored after pressing
    `store_selection_keys`.

Additionally, `expand` contains all conditions provided by `show`.


CONDITION OBJECTS ~

`luasnip.extras.conditions` also contains condition objects. These can, just
like functions, be passed to `condition` or `show_condition`, but can also be
combined with each other into logical expressions:

- `-c1 -> not c1`
- `c1 * c2 -> c1 and c2`
- `c1 + c2 -> c1 or c2`
- `c1 - c2 -> c1 and not c2`: This is similar to set differences:
    `A \ B = {a in A | a not in B}`. This makes `-(a + b) = -a - b` an identity
    representing de Morgan’s law: `not (a or b) = not a and not b`. However,
    since boolean algebra lacks an additive inverse, `a + (-b) = a - b` does not
    hold. Thus, this is NOT the same as `c1 + (-c2)`.
- `c1 ^ c2 -> c1 xor(!=) c2`
- `c1 % c2 -> c1 xnor(==) c2`: This decision may seem weird, considering how
    there is an overload for the `==`-operator. Unfortunately, it’s not possible
    to use this for our purposes (some info
    here <https://github.com/L3MON4D3/LuaSnip/pull/612#issuecomment-1264487743>),
    so we decided to make use of a more obscure symbol (which will hopefully avoid
    false assumptions about its meaning).

This makes logical combinations of conditions very readable. Compare

>lua
    condition = conditions.expand.line_end + conditions.expand.line_begin
<

with the more verbose

>lua
    condition = function(...) return conditions.expand.line_end(...) or conditions.expand.line_begin(...) end
<

The conditions provided in `show` and `expand` are already condition objects.
To create new ones, use
`require("luasnip.extras.conditions").make_condition(condition_fn)`


ON THE FLY-SNIPPETS                       *luasnip-extras-on-the-fly-snippets*

Sometimes it’s desirable to create snippets tailored for exactly the current
situation. For example inserting repetitive, but just slightly different
invocations of some function, or supplying data in some schema.

On-the-fly snippets enable exactly this use case: they can be quickly created
and expanded with as little disruption as possible.

Since they should mainly fast to write and don’t necessarily need all bells
and whistles, they don’t make use of lsp/textmate-syntax, but a more
simplistic one:

- `$anytext` denotes a placeholder (`insertNode`) with text "anytext". The text
    also serves as a unique key: if there are multiple placeholders with the same
    key, only the first will be editable, the others will just mirror it.
- … That’s it. `$` can be escaped by preceding it with a second `$`, all other
    symbols will be interpreted literally.

There is currently only one way to expand on-the-fly snippets:
`require('luasnip.extras.otf').on_the_fly("<some-register>")` will interpret
whatever text is in the register `<some-register>` as a snippet, and expand it
immediately. The idea behind this mechanism is that it enables a very immediate
way of supplying and retrieving (expanding) the snippet: write the snippet-body
into the buffer, cut/yank it into some register, and call
`on_the_fly("<register>")` to expand the snippet.

Here’s one set of example keybindings:

>vim
    " in the first call: passing the register is optional since `on_the_fly`
    " defaults to the unnamed register, which will always contain the previously cut
    " text.
    vnoremap <c-f>  "ec<cmd>lua require('luasnip.extras.otf').on_the_fly("e")<cr>
    inoremap <c-f>  <cmd>lua require('luasnip.extras.otf').on_the_fly("e")<cr>
<

Obviously, `<c-f>` is arbritary and can be changed to any other key combo.
Another interesting application is allowing multiple on-the-fly snippets at the
same time by retrieving snippets from multiple registers:

>vim
    " For register a
    vnoremap <c-f>a  "ac<cmd>lua require('luasnip.extras.otf').on_the_fly()<cr>
    inoremap <c-f>a  <cmd>lua require('luasnip.extras.otf').on_the_fly("a")<cr>
    
    
    " For register b
    vnoremap <c-f>a  "bc<cmd>:lua require('luasnip.extras.otf').on_the_fly()<cr>
    inoremap <c-f>b  <cmd>lua require('luasnip.extras.otf').on_the_fly("b")<cr>
<


SELECT_CHOICE                                   *luasnip-extras-select_choice*

It’s possible to leverage `vim.ui.select` for selecting a choice directly,
without cycling through the available choices. All that is needed for this is
calling `require("luasnip.extras.select_choice")`, most likely via some
keybind, e.g.

>vim
    inoremap <c-u> <cmd>lua require("luasnip.extras.select_choice")()<cr>
<

while inside a choiceNode. The `opts.kind` hint for `vim.ui.select` will be set
to `luasnip`.


FILETYPE-FUNCTIONS                         *luasnip-extras-filetype-functions*

Contains some utility functions that can be passed to the `ft_func` or
`load_ft_func`-settings.

- `from_filetype`: the default for `ft_func`. Simply returns the filetype(s) of
    the buffer.
- `from_cursor_pos`: uses treesitter to determine the filetype at the cursor.
    With that, it’s possible to expand snippets in injected regions, as long as
    the treesitter parser supports them. If this is used in conjuction with
    `lazy_load`, extra care must be taken that all the filetypes that can be
    expanded in a given buffer are also returned by `load_ft_func` (otherwise their
    snippets may not be loaded). This can easily be achieved with `extend_load_ft`.
- `extend_load_ft`: `fn(extend_ft:map) -> fn` A simple solution to the problem
    described above is loading more filetypes than just that of the target buffer
    when `lazy_load`ing. This can be done ergonomically via `extend_load_ft`:
    calling it with a table where the keys are filetypes, and the values are the
    filetypes that should be loaded additionaly returns a function that can be
    passed to `load_ft_func` and takes care of extending the filetypes properly.
    >lua
        ls.setup({
          load_ft_func =
              -- Also load both lua and json when a markdown-file is opened,
              -- javascript for html.
              -- Other filetypes just load themselves.
              require("luasnip.extras.filetype_functions").extend_load_ft({
                  markdown = {"lua", "json"},
                  html = {"javascript"}
              })
        })
    <


POSTFIX-SNIPPET                               *luasnip-extras-postfix-snippet*

Postfix snippets, famously used in rust analyzer
<https://rust-analyzer.github.io/> and various IDEs, are a type of snippet
which alters text before the snippet’s trigger. While these can be
implemented using regTrig snippets, this helper makes the process easier in
most cases.

The simplest example, which surrounds the text preceeding the `.br` with
brackets `[]`, looks like:

>lua
    postfix(".br", {
        f(function(_, parent)
            return "[" .. parent.snippet.env.POSTFIX_MATCH .. "]"
        end, {}),
    })
<

and is triggered with `xxx.br` and expands to `[xxx]`.

Note the `parent.snippet.env.POSTFIX_MATCH` in the function node. This is
additional field generated by the postfix snippet. This field is generated by
extracting the text matched (using a configurable matching string, see below)
from before the trigger. In the case above, the field would equal `"xxx"`. This
is also usable within dynamic nodes.

This field can also be used within lambdas and dynamic nodes.

>lua
    postfix(".br", {
        l("[" .. l.POSTFIX_MATCH .. "]"),
    })
<

>lua
    postfix(".brd", {
        d(1, function (_, parent)
            return sn(nil, {t("[" .. parent.env.POSTFIX_MATCH .. "]")})
        end)
    })
<

The arguments to `postfix` are identical to the arguments to `s` but with a few
extra options.

The first argument can be either a string or a table. If it is a string, that
string will act as the trigger, and if it is a table it has the same valid keys
as the table in the same position for `s` except:

- `wordTrig`: This key will be ignored if passed in, as it must always be
    false for postfix snippets.
- `match_pattern`: The pattern that the line before the trigger is matched
    against. The default match pattern is `"[%w%.%_%-]+$"`. Note the `$`. This
    matches since only the line _up until_ the beginning of the trigger is
    matched against the pattern, which makes the character immediately
    preceeding the trigger match as the end of the string.

Some other match strings, including the default, are available from the postfix
module. `require("luasnip.extras.postfix).matches`:

- `default`: `[%w%.%_%-%"%']+$`
- `line`: `^.+$`

The second argument is identical to the second argument for `s`, that is, a
table of nodes.

The optional third argument is the same as the third (`opts`) argument to the
`s` function, but with one difference:

The postfix snippet works using a callback on the pre_expand event of the
snippet. If you pass a callback on the pre_expand event (structure example
below) it will get run after the builtin callback.

>lua
    {
        callbacks = {
        [-1] = {
            [events.pre_expand] = function(snippet, event_args)
            -- function body to match before the dot
            -- goes here
            end
            }
        }
    }
<


TREESITTER-POSTFIX-SNIPPET         *luasnip-extras-treesitter-postfix-snippet*

Instead of triggering a postfix-snippet when some pattern matches in front of
the trigger, it might be useful to match if some specific treesitter-nodes
surround/are in front of the trigger. While this functionality can also be
implemented by a cusutom `resolveExpandParams`, this helper simplifies the
common cases.

This matching of treesitter-nodes can be done either

- by providing a query and the name of the capture that should be in front of
    the trigger (in most cases, the complete match, but requiring specific nodes
    before/after the matched node may be useful as well), or
- by providing a function that manually walks the node-tree, and returns the
    node in front of the trigger on success (for increased flexibility).

A simple example, which surrounds the previous node’s text preceeding the
`.mv` with `std::move()` in cpp files, looks like:

>lua
    local treesitter_postfix = require("luasnip.extras.treesitter_postfix").treesitter_postfix
    
    treesitter_postfix({
        trig = ".mv",
        matchTSNode = {
            query = [[
                [
                  (call_expression)
                  (identifier)
                  (template_function)
                  (subscript_expression)
                  (field_expression)
                  (user_defined_literal)
                ] @prefix
            ]]
            query_lang = "cpp"
        },
    },{
        f(function(_, parent)
            local node_content = table.concat(parent.snippet.env.LS_TSMATCH, '\n')
            local replaced_content = ("std::move(%s)"):format(node_content)
            return vim.split(ret_str, "\n", { trimempty = false })
        end)
    })
<

`LS_TSMATCH` is the treesitter-postfix equivalent to `POSTFIX_MATCH`, and is
populated with the match (in this case the text of a treesitter-node) in front
of the trigger.

The arguments to `treesitter_postfix` are identical to the arguments to `s` but
with a few extra options.

The first argument has to be a table, which defines at least `trig` and
`matchTSNode`. All keys from the regular `s` may be set here (except for
`wordTrig`, which will be ignored), and additionally the following:

- `reparseBuffer`, `string?`: Sometimes the trigger may interfere with
    treesitter recognizing queries correctly. With this option, the trigger may
    either be removed from the live-buffer (`"live"`), from a copy of the buffer
    (`"copy"`), or not at all (`nil`).
- `matchTSNode`: How to determine whether there is a matching node in front of
    the cursor. There are two options:
    - `fun(parser: LuaSnip.extra.TSParser, pos: { [1]: number, [2]: number }): LuaSnip.extra.NamedTSMatch?, TSNode?   Manually determine whether there is a matching node that ends just before`pos`(the beginning of the trigger).     Return`nil,nil`if there is no match, otherwise first return a table   mapping names to nodes (the text, position and type of these will be   provided via`snip.env`), and second the node that is the matched node.
    - `LuaSnip.extra.MatchTSNodeOpts`, which represents a query and provides all
        captures of the matched pattern in `NamedTSMatch`. It contains the following
        options:
        - `query`, `string`: The query, in textual form.
        - `query_name`, `string`: The name of the runtime-query to be used (passed
            to `query.get()`), defaults to `"luasnip"` (so one could create a
            file which only contains queries used by luasnip, like
            `$CONFDIR/queries/<lang>/luasnip.scm`, which might make sense to define
            general concepts independent of a single snippet).
            `query` and `query_name` are mutually exclusive, only one of both shall be
            defined.
        - `query_lang`, `string`: The language of the query. This is the only
            required parameter to this function, since there’s no sufficiently
            straightforward way to determine the language of the query for us.
            Consider using `extend_override` to define a `ts_postfix`-function that
            automatically fills in the language for the filetype of the snippet-file.
        - `match_captures`, `string|string[]`: The capture(s) to use for determining
            the actual prefix (so the node that should be immediately in front of the
            trigger). This defaults to just `"prefix"`.
        - `select`, `string?|fun(): LuaSnip.extra.MatchSelector`: Since there may be
            multiple matching captures in front of the cursor, there has to be some
            way to select the node that will actually be used.
            If this is a string, it has to be one of "any", "shortest", or "longest",
            which mean that any, the shortest, or the longest match is used.
            If it is a function, it must return a table with two fields, `record` and
            `retrieve`. `record` is called with a TSMatch and a potential node for the
            ts-match, and may return `true` to abort the selection-procedure.
            `retrieve` must return either a TSMatch-TSNode-tuple (which is used as the
            match) or `nil`, to signify that there is no match.
            `lua/luasnip/extras/_treesitter.lua` contains the table
            `builtin_tsnode_selectors`, which contains the implementations for
            any/shortest/longest, which can be used as examples for more complicated
            custom-selectors.

The text of the matched node can be accessed as `snip.env.LS_TSMATCH`. The text
of the nodes returned as `NamedTSMatch` can be accessed as
`snip.env.LS_TSCAPTURE_<node-name-in-caps>`, and their range and type as
`snip.env.LS_TSDATA.<node-name-NOT-in-caps>.range/type` (where range is a tuple
of row-col-tuples, both 0-indexed).

For a query like

>scm
    (function_declaration
      name: (identifier) @fname
      parameters: (parameters) @params
      body: (block) @body
    ) @prefix
<

matched against

>lua
    function add(a, b)
        return a + b
    end
<

`snip.env` would contain:

- `LS_TSMATCH`: `{ "function add(a, b)", "\treturn a + b", "end" }`
- `LS_TSDATA`:
    >lua
        {
          body = {
            range = { { 1, 1 }, { 1, 13 } },
            type = "block"
          },
          fname = {
            range = { { 0, 9 }, { 0, 12 } },
            type = "identifier"
          },
          params = {
            range = { { 0, 12 }, { 0, 18 } },
            type = "parameters"
          },
          prefix = {
            range = { { 0, 0 }, { 2, 3 } },
            type = "function_declaration"
          }
        }
    <
- `LS_TSCAPTURE_FNAME`: `{ "add" }`
- `LS_TSCAPTURE_PARAMS`: `{ "(a, b)" }`
- `LS_TSCAPTURE_BODY`: `{ "return a + b" }`
- `LS_TSCAPTURE_PREFIX`: `{ "function add(a, b)", "\treturn a + b", "end" }`

(note that all variables containing text of nodes are string-arrays, one entry
for each line)

There is one important caveat when accessing `LS_TSDATA` in
function/dynamicNodes: It won’t contain the values as specified here while
generating docstrings (in fact, it won’t even be a table). Since docstrings
have to be generated without any runtime-information, we just have to provide
dummy-data in `env`, which will be some kind of string related to the name of
the env-variable. Since the structure of `LS_TSDATA` obviously does not fit
that model, we can’t really handle it in a nice way (at least yet). So, for
now, best include a check like `local static_evaluation = type(env.LS_TSDATA)
== "string"`, and behave accordingly if `static_evaluation` is true (for
example, return some value tailored for displaying it in a docstring).

One more example, which actually uses a few captures:

>lua
    ts_post({
        matchTSNode = {
            query = [[
                (function_declaration
                  name: (identifier) @fname
                  parameters: (parameters) @params
                  body: (block) @body
                ) @prefix
            ]],
            query_lang = "lua",
        },
        trig = ".var"
    }, fmt([[
        local {} = function{}
            {}
        end
    ]], {
        l(l.LS_TSCAPTURE_FNAME),
        l(l.LS_TSCAPTURE_PARAMS),
        l(l.LS_TSCAPTURE_BODY),
    }))
<

The module `luasnip.extras.treesitter_postfix` contains a few functions that
may be useful for creating more efficient ts-postfix-snippets. Nested in
`builtin.tsnode_matcher` are:

- `fun find_topmost_types(types: string[]): MatchTSNodeFunc`: Generates
    a `LuaSnip.extra.MatchTSNodeFunc` which returns the last parent whose type
    is in `types`.
- `fun find_first_types(types: string[]): MatchTSNodeFunc`: Similar to
    `find_topmost_types`, only this one matches the first parent whose type is in
    types.
- `find_nth_parent(n: number): MatchTSNodeFunc`: Simply matches the `n`-th
    parent of the innermost node infront of the trigger.

With `find_topmost_types`, the first example can be implemented more
efficiently (without needing a whole query):

>lua
    local postfix_builtin = require("luasnip.extras.treesitter_postfix").builtin
    
    ls.add_snippets("all", {
        ts_post({
            matchTSNode = postfix_builtin.tsnode_matcher.find_topmost_types({
                "call_expression",
                "identifier",
                "template_function",
                "subscript_expression",
                "field_expression",
                "user_defined_literal"
            }),
            trig = ".mv"
        }, {
            l(l_str.format("std::move(%s)", l.LS_TSMATCH))
        })
    }, {key = "asdf"})
<


SNIPPET LIST                                     *luasnip-extras-snippet-list*

>lua
    local sl = require("luasnip.extras.snippet_list")
<

Makes an `open` function available to use to open currently available snippets
in a different buffer/window/tab.

`sl.open(opts:table|nil)`

- `opts`: optional arguments:
    - `snip_info`: `snip_info(snippet) -> table representation of snippet`
    - `printer`: `printer(snippets:table) -> any`
    - `display`: `display(snippets:any)`

Benefits include: syntax highlighting, searching, and customizability.

Simple Example:

>lua
    sl.open()
<

Customization Examples:

>lua
    -- making our own snip_info
    local function snip_info(snippet)
        return { name = snippet.name }
    end
    
    -- using it
    sl.open({snip_info = snip_info})
<

>lua
    -- making our own printer
    local function printer(snippets)
        local res = ""
    
        for ft, snips in pairs(snippets) do
            res = res .. ft .. "\n"
            for _, snip in pairs(snips) do
                res = res .. "    " .. "Name: " .. snip.name .. "\n"
                res = res .. "    " .. "Desc: " .. snip.description[1] .. "\n"
                res = res .. "    " .. "Trigger: " .. snip.trigger .. "\n"
                res = res .. "    ----" .. "\n"
            end
        end
    
        return res
    end
    
    
    -- using it
    sl.open({printer = printer})
<

>lua
    -- making our own display
    local function display(printer_result)
        -- right vertical split
        vim.cmd("botright vnew")
    
        -- get buf and win handle
        local buf = vim.api.nvim_get_current_buf()
        local win = vim.api.nvim_get_current_win()
    
        -- setting window and buffer options
        vim.api.nvim_win_set_option(win, "foldmethod", "manual")
        vim.api.nvim_buf_set_option(buf, "filetype", "javascript")
    
        vim.api.nvim_buf_set_option(buf, "buftype", "nofile")
        vim.api.nvim_buf_set_option(buf, "bufhidden", "wipe")
        vim.api.nvim_buf_set_option(buf, "buflisted", false)
    
        vim.api.nvim_buf_set_name(buf, "Custom Display buf " .. buf)
    
        -- dump snippets
        local replacement = vim.split(printer_result)
        vim.api.nvim_buf_set_lines(buf, 0, 0, false, replacement)
    end
    
    -- using it
    sl.open({display = display})
<

There is a **caveat** with implementing your own printer and/or display
function. The **default** behavior for the printer function is to return a
string representation of the snippets. The display function uses the results
from the printer function, therefore by **default** the display function is
expecting that result to be a string.

However, this doesn’t have to be the case. For example, you can implement
your own printer function that returns a table representation of the snippets
**but** you would have to then implement your own display function or some
other function in order to return the result as a string.

An `options` table, which has some core functionality that can be used to
customize 'common' settings, is provided.

- `sl.options`: options table:
    - `display`: `display(opts:table|nil) -> function(printer_result:string)`

You can see from the example above that making a custom display is a fairly
involved process. What if you just wanted to change a buffer option like the
name or just the filetype? This is where `sl.options.display` comes in. It
allows you to customize buffer and window options while keeping the default
behavior.

`sl.options.display(opts:table|nil) -> function(printer_result:string)`

- `opts`: optional arguments:
    - `win_opts`: `table which has a {window_option = value} form`
    - `buf_opts`: `table which has a {buffer_option = value} form`
    - `get_name`: `get_name(buf) -> string`

Let’s recreate the custom display example above:

>lua
    -- keeping the default display behavior but modifying window/buffer
    local modified_default_display = sl.options.display({
            buf_opts = {filetype = "javascript"},
            win_opts = {foldmethod = "manual"},
            get_name = function(buf) return "Custom Display buf " .. buf end
        })
    
    -- using it
    sl.open({display = modified_default_display})
<


SNIPPET LOCATION                             *luasnip-extras-snippet-location*

This module can consume a snippets |luasnip-source|, more specifically, jump to
the location referred by it. This is primarily implemented for snippet which
got their source from one of the loaders, but might also work for snippets
where the source was set manually.

`require("luasnip.extras.snip_location")`:

- `snip_location.jump_to_snippet(snip, opts)`
    Jump to the definition of `snip`.
    - `snip`: a snippet with attached source-data.
    - `opts`: `nil|table`, optional arguments, valid keys are:
        - `hl_duration_ms`: `number`, duration for which the definition should be highlighted,
            in milliseconds. 0 disables the highlight.
        - `edit_fn`: `function(file)`, this function will be called with the file
            the snippet is located in, and is responsible for jumping to it.
            We assume that after it has returned, the current buffer contains `file`.
- `snip_location.jump_to_active_snippet(opts)`
    Jump to definition of active snippet.
    - `opts`: `nil|table`, accepts the same keys as the `opts`-parameter of
        `jump_to_snippet`.


==============================================================================
17. Extend Decorator                                *luasnip-extend-decorator*

Most of luasnip’s functions have some arguments to control their behaviour.
Examples include `s`, where `wordTrig`, `regTrig`, … can be set in the first
argument to the function, or `fmt`, where the delimiter can be set in the third
argument. This is all good and well, but if these functions are often used with
non-default settings, it can become cumbersome to always explicitly set them.

This is where the `extend_decorator` comes in: it can be used to create
decorated functions which always extend the arguments passed directly with
other previously defined ones.

An example:

>lua
    local fmt = require("luasnip.extras.fmt").fmt
    
    fmt("{}", {i(1)}) -- -> list of nodes, containing just the i(1).
    
    -- when authoring snippets for some filetype where `{` and `}` are common, they
    -- would always have to be escaped in the format-string. It might be preferable
    -- to use other delimiters, like `<` and `>`.
    
    fmt("<>", {i(1)}, {delimiters = "<>"}) -- -> same as above.
    
    -- but it's quite annoying to always pass the `{delimiters = "<>"}`.
    
    -- with extend_decorator:
    local fmt_angle = ls.extend_decorator.apply(fmt, {delimiters = "<>"})
    fmt_angle("<>", {i(1)}) -- -> same as above.
    
    -- the same also works with other functions provided by luasnip, for example all
    -- node/snippet-constructors and `parse_snippet`.
<

`extend_decorator.apply(fn, ...)` requires that `fn` is previously registered
via `extend_decorator.register`. (This is not limited to LuaSnip’s functions;
although, for usage outside of LuaSnip, best copy the source file:
`/lua/luasnip/util/extend_decorator.lua`).

`register(fn, ...)`:

- `fn`: the function.
- `...`: any number of tables. Each specifies how to extend an argument of `fn`.
    The tables accept:
    - arg_indx, `number` (required): the position of the parameter to override.
    - extend, `fn(arg, extend_value) -> effective_arg` (optional): this function
        is used to extend the args passed to the decorated function.
        It defaults to a function which just extends the the arg-table with the
        extend table (accepts `nil`).
        This extend behaviour is adaptable to accomodate `s`, where the first
        argument may be string or table.

`apply(fn, ...) -> decorated_fn`:

- `fn`: the function to decorate.
- `...`: The values to extend with. These should match the descriptions passed
    in `register` (the argument first passed to `register` will be extended with
    the first value passed here).

One more example for registering a new function:

>lua
    local function somefn(arg1, arg2, opts1, opts2)
        -- not important
    end
    
    -- note the reversed arg_indx!!
    extend_decorator.register(somefn, {arg_indx=4}, {arg_indx=3})
    local extended = extend_decorator.apply(somefn,
        {key = "opts2 is extended with this"},
        {key = "and opts1 with this"})
    extended(...)
<


==============================================================================
18. LSP-Snippets                                        *luasnip-lsp-snippets*

LuaSnip is capable of parsing LSP-style snippets using
`ls.parser.parse_snippet(context, snippet_string, opts)`:

>lua
    ls.parser.parse_snippet({trig = "lsp"}, "$1 is ${2|hard,easy,challenging|}")
<

`context` can be: - `string|table`: treated like the first argument to `ls.s`,
`parse_snippet` returns a snippet. - `number`: `parse_snippet` returns a
snippetNode, with the position `context`. - `nil`: `parse_snippet` returns a
flat table of nodes. This can be used like `fmt`.

Nested placeholders(`"${1:this is ${2:nested}}"`) will be turned into
choiceNodes with: - the given snippet(`"this is ${1:nested}"`) and - an empty
insertNode

This behaviour can be modified by changing `parser_nested_assembler` in
`ls.setup()`.

LuaSnip will also modify some snippets that it is incapable of representing
accurately:

- if the `$0` is a placeholder with something other than just text inside
- if the `$0` is a choice
- if the `$0` is not an immediate child of the snippet (it could be inside a
    placeholder: `"${1: $0 }"`)

To remedy those incompatibilities, the invalid `$0` will be replaced with a
tabstop/placeholder/choice which will be visited just before the new `$0`. This
new `$0` will be inserted at the (textually) earliest valid position behind the
invalid `$0`.

`opts` can contain the following keys: - `trim_empty`: boolean, remove empty
lines from the snippet. Default true. - `dedent`: boolean, remove common indent
from the snippet’s lines. Default true.

Both `trim_empty` and `dedent` will be disabled for snippets parsed via
`ls.lsp_expand`: it might prevent correct expansion of snippets sent by lsp.


SNIPMATE PARSER                         *luasnip-lsp-snippets-snipmate-parser*

It is furthermore possible to parse SnipMate snippets (this includes support
for vimscript-evaluation!!)

SnipMate snippets need to be parsed with a different function,
`ls.parser.parse_snipmate`:

>lua
    ls.parser.parse_snipmate("year", "The year is `strftime('%Y')`")
<

`parse_snipmate` accepts the same arguments as `parse_snippet`, only the
snippet body is parsed differently.


TRANSFORMATIONS                         *luasnip-lsp-snippets-transformations*

To apply Variable/Placeholder-transformations
<https://code.visualstudio.com/docs/editor/userdefinedsnippets#_variable-transforms>,
luasnip needs to apply ECMAScript regexes. This is implemented by relying on
`jsregexp` <https://github.com/kmarius/jsregexp>.

The easiest (but potentially error-prone) way to install it is by calling `make
install_jsregexp` in the repo root.

This process can be automated by `packer.nvim`:

>lua
    use { "L3MON4D3/LuaSnip", run = "make install_jsregexp" }
<

If this fails, first open an issue :P, and then try installing the
`jsregexp`-luarock. This is also possible via `packer.nvim`, although actual
usage may require a small workaround, see here
<https://github.com/wbthomason/packer.nvim/issues/593> or here
<https://github.com/wbthomason/packer.nvim/issues/358>.

Alternatively, `jsregexp` can be cloned locally, `make`d, and the resulting
`jsregexp.so` placed in some place where nvim can find it (probably
`~/.config/nvim/lua/`).

If `jsregexp` is not available, transformations are replaced by a simple copy.


==============================================================================
19. Variables                                              *luasnip-variables*

All `TM_something`-variables are supported with two additions: `LS_SELECT_RAW`
and `LS_SELECT_DEDENT`. These were introduced because `TM_SELECTED_TEXT` is
designed to be compatible with VSCode’s behavior, which can be
counterintuitive when the snippet can be expanded at places other than the
point where selection started (or when doing transformations on selected text).
Besides those we also provide `LS_TRIGGER` which contains the trigger of the
snippet, and `LS_CAPTURE_n` (where n is a positive integer) that contains the
n-th capture when using a regex with capture groups as `trig` in the snippet
definition.

All variables can be used outside of lsp-parsed snippets as their values are
stored in a snippets’ `snip.env`-table:

>lua
    s("selected_text", f(function(args, snip)
      local res, env = {}, snip.env
      table.insert(res, "Selected Text (current line is " .. env.TM_LINE_NUMBER .. "):")
      for _, ele in ipairs(env.LS_SELECT_RAW) do table.insert(res, ele) end
      return res
    end, {}))
<

To use any `*SELECT*` variable, the `store_selection_keys` must be set via
`require("luasnip").config.setup({store_selection_keys="<Tab>"})`. In this
case, hitting `<Tab>` while in visual mode will populate the `*SELECT*`-vars
for the next snippet and then clear them.


ENVIRONMENT NAMESPACES              *luasnip-variables-environment-namespaces*

You can also add your own variables by using the `ls.env_namespace(name, opts)`
where:

- `name`: `string` the names the namespace, can’t contain the character “_”
- `opts` is a table containing (in every case `EnvVal` is the same as `string|list[string]`:
    - `vars`: `(fn(name:string)->EnvVal) | map[string, EnvVal]`
        Is a function that receives a string and returns a value for the var with that name
        or a table from var name to a value
        (in this case, if the value is a function it will be executed lazily once per snippet expansion).
    - `init`: `fn(info: table)->map[string, EnvVal]` Returns
        a table of variables that will set to the environment of the snippet on expansion,
        use this for vars that have to be calculated in that moment or that depend on each other.
        The `info` table argument contains `pos` (0-based position of the cursor on expansion),
        the `trigger` of the snippet and the `captures` list.
    - `eager`: `list[string]` names of variables that will be taken from `vars` and appended eagerly (like those in init)
    - `multiline_vars`: `(fn(name:string)->bool)|map[sting, bool]|bool|string[]` Says if certain vars are a table or just a string,
        can be a function that get’s the name of the var and returns true if the var is a key,
        a list of vars that are tables or a boolean for the full namespace, it’s false by default. Refer to
        issue#510 <https://github.com/L3MON4D3/LuaSnip/issues/510#issuecomment-1209333698> for more information.

The four fields of `opts` are optional but you need to provide either `init` or
`vars`, and `eager` can’t be without `vars`. Also, you can’t use namespaces
that override default vars.

A simple example to make it more clear:

>lua
    local function random_lang()
        return ({"LUA", "VIML", "VIML9"})[math.floor(math.random()/2 + 1.5)]
    end
    
    ls.env_namespace("MY", {vars={ NAME="LuaSnip",  LANG=random_lang }})
    
    -- then you can use  $MY_NAME and $MY_LANG in your snippets
    
    ls.env_namespace("SYS", {vars=os.getenv, eager={"HOME"}})
    
    -- then you can use  $SYS_HOME which was eagerly initialized but also $SYS_USER (or any other system environment var) in your snippets
    
    lsp.env_namespace("POS", {init=function(info) return {VAL=vim.inspect(info.pos)} end})
    
    -- then you can use  $POS_VAL in your snippets
    
    s("custom_env", d(1, function(args, parent)
      local env = parent.snippet.env
      return sn(nil, t {
        "NAME: " .. env.MY_NAME,
        "LANG: " .. env.MY_LANG,
        "HOME: " .. env.SYS_HOME,
        "USER: " .. env.SYS_USER,
        "VAL: " .. env.POS_VAL
      })
    end, {}))
<


LSP-VARIABLES                                *luasnip-variables-lsp-variables*

All variables, even ones added via `env_namespace`, can be accessed in LSP
snippets as `$VAR_NAME`.

The lsp-spec states:

------------------------------------------------------------------------------
With `$name` or `${name:default}` you can insert the value of a variable. When
a variable isn’t set, its default or the empty string is inserted. When a
variable is unknown (that is, its name isn’t defined) the name of the
variable is inserted and it is transformed into a placeholder.

------------------------------------------------------------------------------
The above necessiates a differentiation between `unknown` and `unset`
variables:

For LuaSnip, a variable `VARNAME` is `unknown` when `env.VARNAME` returns `nil`
and `unset` if it returns an empty string.

Consider this when adding env-variables which might be used in LSP snippets.


==============================================================================
20. Loaders                                                  *luasnip-loaders*

Luasnip is capable of loading snippets from different formats, including both
the well-established VSCode and SnipMate format, as well as plain Lua files for
snippets written in Lua.

All loaders (except the vscode-standalone-loader) share a similar interface:
`require("luasnip.loaders.from_{vscode,snipmate,lua}").{lazy_,}load(opts:table|nil)`

where `opts` can contain the following keys:

- `paths`: List of paths to load. Can be a table, or a single
    comma-separated string.
    The paths may begin with `~/` or `./` to indicate that the path is
    relative to your `$HOME` or to the directory where your `$MYVIMRC` resides
    (useful to add your snippets).
    If not set, `runtimepath` is searched for
    directories that contain snippets. This procedure differs slightly for
    each loader:
    - `lua`: the snippet-library has to be in a directory named
        `"luasnippets"`.
    - `snipmate`: similar to lua, but the directory has to be `"snippets"`.
    - `vscode`: any directory in `runtimepath` that contains a
        `package.json` contributing snippets.
- `lazy_paths`: behaves essentially like `paths`, with two exceptions: if it is
    `nil`, it does not default to `runtimepath`, and the paths listed here do not
    need to exist, and will be loaded on creation.
    LuaSnip will do its best to determine the path that this should resolve to,
    but since the resolving we do is not very sophisticated it may produce
    incorrect paths. Definitely check the log if snippets are not loaded as
    expected.
- `exclude`: List of languages to exclude, empty by default.
- `include`: List of languages to include, includes everything by default.
- `{override,default}_priority`: These keys are passed straight to the
    `add_snippets`-calls (documented in |luasnip-api|) and can therefore change the
    priority of snippets loaded from some colletion (or, in combination with
    `{in,ex}clude`, only some of its snippets).
- `fs_event_providers`: `table<string, boolean>?`, specifies which mechanisms
    should be used to watch files for updates/creation.
    If `autocmd` is set to `true`, a `BufWritePost`-hook watches files of this
    collection, if `libuv` is set, the file-watcher-api exposed by libuv is used
    to watch for updates.
    Use `libuv` if you want snippets to update from other neovim-instances, and
    `autocmd` if the collection resides on a filesystem where the libuv-watchers
    may not work correctly. Or, of course, just enable both :D
    By default, only `autocmd` is enabled.

While `load` will immediately load the snippets, `lazy_load` will defer loading
until the snippets are actually needed (whenever a new buffer is created, or
the filetype is changed luasnip actually loads `lazy_load`ed snippets for the
filetypes associated with this buffer. This association can be changed by
customizing `load_ft_func` in `setup`: the option takes a function that, passed
a `bufnr`, returns the filetypes that should be loaded (`fn(bufnr) -> filetypes
(string[])`)).

All of the loaders support reloading, so simply editing any file contributing
snippets will reload its snippets (according to `fs_event_providers` in the
instance where the file was edited, or in other instances as well).

As an alternative (or addition) to automatic reloading, luasnip can also
process manual updates to files: Call
`require("luasnip.loaders").reload_file(path)` to reload the file at `path`.
This may be useful when the collection is controlled by some other plugin, or
when enabling the other reload-mechanisms is for some reason undesirable
(performance? minimalism?).

For easy editing of these files, LuaSnip provides a `vim.ui.select`-based
dialog (|luasnip-loaders-edit_snippets|) where first the filetype, and then the
file can be selected.


SNIPPET-SPECIFIC FILETYPES        *luasnip-loaders-snippet-specific-filetypes*

Some loaders (vscode,lua) support giving snippets generated in some file their
own filetype (vscode via `scope`, lua via the underlying `filetype`-option for
snippets). These snippet-specific filetypes are not considered when determining
which files to `lazy_load` for some filetype, this is exclusively determined by
the `language` associated with a file in vscodes’ `package.json`, and the
file/directory-name in lua.

- This can be resolved relatively easily in vscode, where the `language`
    advertised in `package.json` can just be a superset of the `scope`s in the file.
- Another simplistic solution is to set the language to `all` (in lua, it might
    make sense to create a directory `luasnippets/all/*.lua` to group these files
    together).
- Another approach is to modify `load_ft_func` to load a custom filetype if the
    snippets should be activated, and store the snippets in a file for that
    filetype. This can be used to group snippets by e.g. framework, and load them
    once a file belonging to such a framework is edited.

**Example**: `react.lua`

>lua
    return {
        s({filetype = "css", trig = ...}, ...),
        s({filetype = "html", trig = ...}, ...),
        s({filetype = "js", trig = ...}, ...),
    }
<

`luasnip_config.lua`

>lua
    load_ft_func = function(bufnr)
        if "<bufnr-in-react-framework>" then
            -- will load `react.lua` for this buffer
            return {"react"}
        else
            return require("luasnip.extras.filetype_functions").from_filetype_load
        end
    end
<

See the |luasnip-troubleshooting-adding-snippets-loaders| section if one is
having issues adding snippets via loaders.


VS-CODE                                              *luasnip-loaders-vs-code*

As a reference on the structure of these snippet libraries, see
`friendly-snippets` <https://github.com/rafamadriz/friendly-snippets>.

We support a small extension: snippets can contain LuaSnip-specific options in
the `luasnip`-table:

>json
    "example1": {
        "prefix": "options",
        "body": [
            "whoa! :O"
        ],
        "luasnip": {
            "priority": 2000,
            "autotrigger": true,
            "wordTrig": false
        }
    }
<

Files with the extension `jsonc` will be parsed as `jsonc`, json with comments
<https://code.visualstudio.com/docs/languages/json#_json-with-comments>, while
`*.json` are parsed with a regular `json` parser, where comments are
disallowed. (the json-parser is a bit faster, so don’t default to `jsonc` if
it’s not necessary).

**Example**:

`~/.config/nvim/my_snippets/package.json`:

>json
    {
        "name": "example-snippets",
        "contributes": {
            "snippets": [
                {
                    "language": [
                        "all"
                    ],
                    "path": "./snippets/all.json"
                },
                {
                    "language": [
                        "lua"
                    ],
                    "path": "./lua.json"
                }
            ]
        }
    }
<

`~/.config/nvim/my_snippets/snippets/all.json`:

>json
    {
        "snip1": {
            "prefix": "all1",
            "body": [
                "expands? jumps? $1 $2 !"
            ]
        },
        "snip2": {
            "prefix": "all2",
            "body": [
                "multi $1",
                "line $2",
                "snippet$0"
            ]
        }
    }
<

`~/.config/nvim/my_snippets/lua.json`:

>json
    {
        "snip1": {
            "prefix": "lua",
            "body": [
                "lualualua"
            ]
        }
    }
<

This collection can be loaded with any of

>lua
    -- don't pass any arguments, luasnip will find the collection because it is
    -- (probably) in rtp.
    require("luasnip.loaders.from_vscode").lazy_load()
    -- specify the full path...
    require("luasnip.loaders.from_vscode").lazy_load({paths = "~/.config/nvim/my_snippets"})
    -- or relative to the directory of $MYVIMRC
    require("luasnip.loaders.from_vscode").load({paths = "./my_snippets"})
<


STANDALONE ~

Beside snippet-libraries provided by packages, vscode also supports another
format which can be used for project-local snippets, or user-defined snippets,
`.code-snippets`.

The layout of these files is almost identical to that of the package-provided
snippets, but there is one additional field supported in the
snippet-definitions, `scope`, with which the filetype of the snippet can be
set. If `scope` is not set, the snippet will be added to the global filetype
(`all`).

`require("luasnip.loaders.from_vscode").load_standalone(opts)`

- `opts`: `table`, can contain the following keys:
    - `path`: `string`, Path to the `*.code-snippets`-file that should be loaded.
        Just like the paths in `load`, this one can begin with a `"~/"` to be
        relative to `$HOME`, and a `"./"` to be relative to the
        neovim-config-directory.
    - `{override,default}_priority`: These keys are passed straight to the
        `add_snippets`-calls (documented in |luasnip-api|) and can be used to change
        the priority of the loaded snippets.
    - `lazy`: `boolean`, if it is set, the file does not have to exist when
        `load_standalone` is called, and it will be loaded on creation.
        `false` by default.

**Example**: `a.code-snippets`:

>jsonc
    {
        // a comment, since `.code-snippets` may contain jsonc.
        "c/cpp-snippet": {
            "prefix": [
                "trigger1",
                "trigger2"
            ],
            "body": [
                "this is $1",
                "my snippet $2"
            ],
            "description": "A description of the snippet.",
            "scope": "c,cpp"
        },
        "python-snippet": {
            "prefix": "trig",
            "body": [
                "this is $1",
                "a different snippet $2"
            ],
            "description": "Another snippet-description.",
            "scope": "python"
        },
        "global snippet": {
            "prefix": "trigg",
            "body": [
                "this is $1",
                "the last snippet $2"
            ],
            "description": "One last snippet-description.",
        }
    }
<

This file can be loaded by calling

>lua
    require("luasnip.loaders.from_vscode").load_standalone({path = "a.code-snippets"})
<


SNIPMATE                                            *luasnip-loaders-snipmate*

Luasnip does not support the full snipmate format: Only `./{ft}.snippets` and
`./{ft}/*.snippets` will be loaded. See honza/vim-snippets
<https://github.com/honza/vim-snippets> for lots of examples.

Like VSCode, the SnipMate format is also extended to make use of some of
LuaSnip’s more advanced capabilities:

>snippets
    priority 2000
    autosnippet options
        whoa :O
<

**Example**:

`~/.config/nvim/snippets/c.snippets`:

>snippets
    # this is a comment
    snippet c c-snippet
        c!
<

`~/.config/nvim/snippets/cpp.snippets`:

>snippets
    extends c
    
    snippet cpp cpp-snippet
        cpp!
<

This can, again, be loaded with any of

>lua
    require("luasnip.loaders.from_snipmate").load()
    -- specify the full path...
    require("luasnip.loaders.from_snipmate").lazy_load({paths = "~/.config/nvim/snippets"})
    -- or relative to the directory of $MYVIMRC
    require("luasnip.loaders.from_snipmate").lazy_load({paths = "./snippets"})
<

Stuff to watch out for:

- Using both `extends <ft2>` in `<ft1>.snippets` and
    `ls.filetype_extend("<ft1>", {"<ft2>"})` leads to duplicate snippets.
- `${VISUAL}` will be replaced by `$TM_SELECTED_TEXT` to make the snippets
    compatible with LuaSnip
- We do not implement eval using ` (backtick). This may be implemented in the
    future.


LUA                                                      *luasnip-loaders-lua*

Instead of adding all snippets via `add_snippets`, it’s possible to store
them in separate files and load all of those. The file-structure here is
exactly the supported snipmate-structure, e.g. `<ft>.lua` or `<ft>/*.lua` to
add snippets for the filetype `<ft>`.

There are two ways to add snippets:

- the files may return two lists of snippets, the snippets in the first are all
    added as regular snippets, while the snippets in the second will be added as
    autosnippets (both are the defaults, if a snippet defines a different
    `snippetType`, that will have preference)
- snippets can also be appended to the global (only for these files - they are
    not visible anywhere else) tables `ls_file_snippets` and
    `ls_file_autosnippets`. This can be combined with a custom `snip_env` to define
    and add snippets with one function call:
    >lua
        ls.setup({
          snip_env = {
              s = function(...)
                  local snip = ls.s(...)
                  -- we can't just access the global `ls_file_snippets`, since it will be
                  -- resolved in the environment of the scope in which it was defined.
                  table.insert(getfenv(2).ls_file_snippets, snip)
              end,
              parse = function(...)
                  local snip = ls.parser.parse_snippet(...)
                  table.insert(getfenv(2).ls_file_snippets, snip)
              end,
              -- remaining definitions.
              ...
          },
          ...
        })
    <
    This is more flexible than the previous approach since the snippets don’t
    have to be collected; they just have to be defined using the above `s` and
    `parse`.

As defining all of the snippet constructors (`s`, `c`, `t`, …) in every file
is rather cumbersome, LuaSnip will bring some globals into scope for executing
these files. By default, the names from `luasnip.config.snip_env`
<https://github.com/L3MON4D3/LuaSnip/blob/master/lua/luasnip/config.lua#L22-L48>
will be used, but it’s possible to customize them by setting `snip_env` in
`setup`.

**Example**:

`~/snippets/all.lua`:

>lua
    return {
        s("trig", t("loaded!!"))
    }
<

`~/snippets/c.lua`:

>lua
    return {
        s("ctrig", t("also loaded!!"))
    }, {
        s("autotrig", t("autotriggered, if enabled"))
    }
<

Load via

>lua
    require("luasnip.loaders.from_lua").load({paths = "~/snippets"})
<


RELOADING WHEN EDITING REQUIRE’D FILES ~

While the lua-snippet-files will be reloaded on edit, this does not
automatically happen if a file the snippet-file depends on (eg. via `require`)
is changed. Since this still may still be desirable, there are two functions
exposed when a file is loaded by the lua-loader: `ls_tracked_dofile` and
`ls_tracked_dopackage`. They perform like `dofile` and (almost like) `require`,
but both register the loaded file internally as a dependency of the
snippet-file, so it can be reloaded when the loaded file is edited. As stated,
`ls_tracked_dofile` behaves exactly like `dofile`, but does the dependency-work
as well. `ls_tracked_dopackage` mimics `require` in that it does not take a
path, but a module-name like `"luasnip.loaders.from_lua"`, and then searches
the `runtimepath/lua`-directories, and path and cpath for the module. Unlike
`require`, the file will not be cached, since that would complicate the
reload-on-edit-behaviour.


EDIT_SNIPPETS                                  *luasnip-loaders-edit_snippets*

To easily edit snippets for the current session, the files loaded by any loader
can be quickly edited via
`require("luasnip.loaders").edit_snippet_files(opts:table|nil)`

When called, it will open a `vim.ui.select`-dialog to select first a filetype,
and then (if there are multiple) the associated file to edit.

`opts` contains four settings:

- `ft_filter`: `fn(filetype:string) -> bool` Optionally filter initially listed
    filetypes. `true` -> filetype will be listed, `false` -> not listed. Accepts
    all filetypes by default.
- `format`: `fn(file:string, source_name:string) -> string|nil` `file` is simply
    the path to the file, `source_name` is one of `"lua"`, `"snipmate"` or
    `"vscode"`. If a string is returned, it is used as the title of the item, `nil`
    on the other hand will filter out this item. The default simply replaces some
    long strings (packer-path and config-path) in `file` with shorter, symbolic
    names (`"$PLUGINS"`, `"$CONFIG"`), but this can be extended to
    - filter files from some specific source/path
    - more aggressively shorten paths using symbolic names, e.g.
        `"$FRIENDLY_SNIPPETS"`. Example: hide the `*.lua` snippet files, and shorten
        the path with `$LuaSnip`:
        >lua
            require "luasnip.loaders" .edit_snippet_files {
              format = function(file, source_name)
                if source_name == "lua" then return nil
                else return file:gsub("/root/.config/nvim/luasnippets", "$LuaSnip")
                end
              end
            }
        <
- `edit`: `fn(file:string)` This function is supposed to open the file for
    editing. The default is a simple `vim.cmd("edit " .. file)` (replace the
    current buffer), but one could open the file in a split, a tab, or a floating
    window, for example.
- `extend`: `fn(ft:string, ft_paths:string[]) -> (string,string)[]` This function
    can be used to create additional choices for the file-selection.
    - `ft`: The filetype snippet-files are queried for.
    - `ft_paths`: list of paths to the known snippet files.
    The function should return a list of `(string,string)`-tuples. The first of
    each pair is the label that will appear in the selection-prompt, and the second
    is the path that will be passed to the `edit()` function if that item was
    selected.
    This can be used to create a new snippet file for the current filetype:
    >lua
        require("luasnip.loaders").edit_snippet_files {
        extend = function(ft, paths)
          if #paths == 0 then
            return {
              { "$CONFIG/" .. ft .. ".snippets",
                string.format("%s/%s.snippets", <PERSONAL_SNIPPETS_FOLDER>, ft) }
            }
          end
        
          return {}
        end
        }
    <

One comfortable way to call this function is registering it as a command:

>vim
    command! LuaSnipEdit :lua require("luasnip.loaders").edit_snippet_files()
<


==============================================================================
21. SnippetProxy                                        *luasnip-snippetproxy*

`SnippetProxy` is used internally to alleviate the upfront cost of loading
snippets from e.g. a SnipMate library or a VSCode package. This is achieved by
only parsing the snippet on expansion, not immediately after reading it from
some file. `SnippetProxy` may also be used from Lua directly to get the same
benefits:

This will parse the snippet on startup:

>lua
    ls.parser.parse_snippet("trig", "a snippet $1!")
<

while this will parse the snippet upon expansion:

>lua
    local sp = require("luasnip.nodes.snippetProxy")
    sp("trig", "a snippet $1")
<

`sp(context, body, opts) -> snippetProxy`

- `context`: exactly the same as the first argument passed to `ls.s`.
- `body`: the snippet body.
- `opts`: accepts the same `opts` as `ls.s`, with some additions:
    - `parse_fn`: the function for parsing the snippet. Defaults to
        `ls.parser.parse_snippet` (the parser for LSP snippets), an alternative is
        the parser for SnipMate snippets (`ls.parser.parse_snipmate`).


==============================================================================
22. ext_opts                                                *luasnip-ext_opts*

`ext_opts` can be used to set the `opts` (see `nvim_buf_set_extmark`) of the
extmarks used for marking node positions, either globally, per snippet or per
node. This means that they allow highlighting the text inside of nodes, or
adding virtual text to the line the node begins on.

This is an example for the `node_ext_opts` used to set `ext_opts` of single
nodes:

>lua
    local ext_opts = {
        -- these ext_opts are applied when the node is active (e.g. it has been
        -- jumped into, and not out yet).
        active = 
        -- this is the table actually passed to `nvim_buf_set_extmark`.
        {
            -- highlight the text inside the node red.
            hl_group = "GruvboxRed"
        },
        -- these ext_opts are applied when the node is not active, but
        -- the snippet still is.
        passive = {
            -- add virtual text on the line of the node, behind all text.
            virt_text = {{"virtual text!!", "GruvboxBlue"}}
        },
        -- visited or unvisited are applied when a node was/was not jumped into.
        visited = {
            hl_group = "GruvboxBlue"
        },
        unvisited = {
            hl_group = "GruvboxGreen"
        },
        -- and these are applied when both the node and the snippet are inactive.
        snippet_passive = {}
    }
    
    s("trig", {
        i(1, "text1", {
            node_ext_opts = ext_opts
        }),
        i(2, "text2", {
            node_ext_opts = ext_opts
        })
    })
<

In the above example, the text inside the insertNodes is higlighted in green if
they were not yet visited, in blue once they were, and red while they are. The
virtual text "virtual text!!" is visible as long as the snippet is active.

To make defining `ext_opts` less verbose, more specific states inherit from
less specific ones:

- `passive` inherits from `snippet_passive`
- `visited` and `unvisited` from `passive`
- `active` from `visited`

To disable a key from a less specific state, it has to be explicitly set to its
default, e.g. to disable highlighting inherited from `passive` when the node
is `active`, `hl_group` should be set to `None`.

------------------------------------------------------------------------------
As stated earlier, these `ext_opts` can also be applied globally or for an
entire snippet. For this, it’s necessary to specify which kind of node a
given set of `ext_opts` should be applied to:

>lua
    local types = require("luasnip.util.types")
    
    ls.setup({
        ext_opts = {
            [types.insertNode] = {
                active = {...},
                visited = {...},
                passive = {...},
                snippet_passive = {...}
            },
            [types.choiceNode] = {
                active = {...},
                unvisited = {...}
            },
            [types.snippet] = {
                passive = {...}
            }
        }
    })
<

The above applies the given `ext_opts` to all nodes of these types, in all
snippets.

>lua
    local types = require("luasnip.util.types")
    
    s("trig", { i(1, "text1"), i(2, "text2") }, {
        child_ext_opts = {
            [types.insertNode] = {
                passive = {
                    hl_group = "GruvboxAqua"
                }
            }
        }
    })
<

However, the `ext_opts` here are only applied to the `insertNodes` inside this
snippet.

------------------------------------------------------------------------------
By default, the `ext_opts` actually used for a node are created by extending
the `node_ext_opts` with the `effective_child_ext_opts[node.type]` of the
parent, which are in turn the parent’s `child_ext_opts` extended with the
global `ext_opts` (those set `ls.setup`).

It’s possible to prevent both of these merges by passing
`merge_node/child_ext_opts=false` to the snippet/node-opts:

>lua
    ls.setup({
        ext_opts = {
            [types.insertNode] = {
                active = {...}
            }
        }
    })
    
    s("trig", {
        i(1, "text1", {
            node_ext_opts = {
                active = {...}
            },
            merge_node_ext_opts = false
        }),
        i(2, "text2")
    }, {
        child_ext_opts = {
            [types.insertNode] = {
                passive = {...}
            }
        },
        merge_child_ext_opts = false
    })
<

------------------------------------------------------------------------------
The `hl_group` of the global `ext_opts` can also be set via standard highlight
groups:

>lua
    vim.cmd("hi link LuasnipInsertNodePassive GruvboxRed")
    vim.cmd("hi link LuasnipSnippetPassive GruvboxBlue")
    
    -- needs to be called for resolving the effective ext_opts.
    ls.setup({})
<

The names for the used highlight groups are
`"Luasnip<node>{Passive,Active,SnippetPassive}"`, where `<node>` can be any
kind of node in PascalCase (or "Snippet").

------------------------------------------------------------------------------
One problem that might arise when nested nodes are highlighted is that the
highlight of inner nodes should be visible, e.g. above that of nodes they are
nested inside.

This can be controlled using the `priority`-key in `ext_opts`. In
`nvim_buf_set_extmark`, that value is an absolute value, but here it is
relative to some base-priority, which is increased for each nesting level of
snippet(Nodes)s.

Both the initial base-priority and its’ increase and can be controlled using
`ext_base_prio` and `ext_prio_increase`:

>lua
    ls.setup({
        ext_opts = {
            [types.insertNode] = {
                active = {
                    hl_group = "GruvboxBlue",
                    -- the priorities should be \in [0, ext_prio_increase).
                    priority = 1
                }
            },
            [types.choiceNode] = {
                active = {
                    hl_group = "GruvboxRed"
                    -- priority defaults to 0
                }
            }
        }
        ext_base_prio = 200,
        ext_prio_increase = 2
    })
<

Here the highlight of an insertNode nested directly inside a choiceNode is
always visible on top of it.


==============================================================================
23. Docstrings                                            *luasnip-docstrings*

Snippet docstrings can be queried using `snippet:get_docstring()`. The function
evaluates the snippet as if it was expanded regularly, which can be problematic
if e.g. a dynamicNode in the snippet relies on inputs other than the argument
nodes. `snip.env` and `snip.captures` are populated with the names of the
queried variable and the index of the capture respectively
(`snip.env.TM_SELECTED_TEXT` -> `'$TM_SELECTED_TEXT'`, `snip.captures[1]` ->
`'$CAPTURES1'`). Although this leads to more expressive docstrings, it can
cause errors in functions that e.g. rely on a capture being a number:

>lua
    s({trig = "(%d)", regTrig = true}, {
        f(function(args, snip)
            return string.rep("repeatme ", tonumber(snip.captures[1]))
        end, {})
    })
<

This snippet works fine because `snippet.captures[1]` is always a number.
During docstring generation, however, `snippet.captures[1]` is `'$CAPTURES1'`,
which will cause an error in the functionNode. Issues with `snippet.captures`
can be prevented by specifying `docTrig` during snippet-definition:

>lua
    s({trig = "(%d)", regTrig = true, docTrig = "3"}, {
        f(function(args, snip)
            return string.rep("repeatme ", tonumber(snip.captures[1]))
        end, {})
    })
<

`snippet.captures` and `snippet.trigger` will be populated as if actually
triggered with `3`.

Other issues will have to be handled manually by checking the contents of e.g.
`snip.env` or predefining the docstring for the snippet:

>lua
    s({trig = "(%d)", regTrig = true, docstring = "repeatmerepeatmerepeatme"}, {
        f(function(args, snip)
            return string.rep("repeatme ", tonumber(snip.captures[1]))
        end, {})
    })
<

Refer to #515 <https://github.com/L3MON4D3/LuaSnip/pull/515> for a better
example to understand `docTrig` and `docstring`.


==============================================================================
24. Docstring-Cache                                  *luasnip-docstring-cache*

Although generation of docstrings is pretty fast, it’s preferable to not redo
it as long as the snippets haven’t changed. Using
`ls.store_snippet_docstrings(snippets)` and its counterpart
`ls.load_snippet_docstrings(snippets)`, they may be serialized from or
deserialized into the snippets. Both functions accept a table structsured like
this: `{ft1={snippets}, ft2={snippets}}`. Such a table containing all snippets
can be obtained via `ls.get_snippets()`. `load` should be called before any of
the `loader`-functions as snippets loaded from VSCode style packages already
have their `docstring` set (`docstrings` wouldn’t be overwritten, but
there’d be unnecessary calls).

The cache is located at `stdpath("cache")/luasnip/docstrings.json` (probably
`~/.cache/nvim/luasnip/docstrings.json`).


==============================================================================
25. Events                                                    *luasnip-events*

Events can be used to react to some action inside snippets. These callbacks can
be defined per snippet (`callbacks`-key in snippet constructor), per-node by
passing them as `node_callbacks` in `node_opts`, or globally (autocommand).

`callbacks`: `fn(node[, event_args]) -> event_res` All callbacks receive the
`node` associated with the event and event-specific optional arguments,
`event_args`. `event_res` is only used in one event, `pre_expand`, where some
properties of the snippet can be changed. If multiple callbacks return
`event_res`, we only guarantee that one of them will be effective, not all of
them.

`autocommand`: Luasnip uses `User`-events. Autocommands for these can be
registered using

>vim
    au User SomeUserEvent echom "SomeUserEvent was triggered"
<

or

>lua
    vim.api.nvim_create_autocommand("User", {
        patter = "SomeUserEvent",
        command = "echom SomeUserEvent was triggered"
    })
<

The node and `event_args` can be accessed through `require("luasnip").session`:

- `node`: `session.event_node`
- `event_args`: `session.event_args`

**Events**:

- `enter/leave`: Called when a node is entered/left (for example when jumping
    around in a snippet).
    `User-event`: `"Luasnip<Node>{Enter,Leave}"`, with `<Node>` in
    PascalCase, e.g. `InsertNode` or `DynamicNode`.
    `event_args`: none
- `change_choice`: When the active choice in a choiceNode is changed.
    `User-event`: `"LuasnipChangeChoice"`
    `event_args`: none
- `pre_expand`: Called before a snippet is expanded. Modifying text is allowed,
    the expand-position will be adjusted so the snippet expands at the same
    position relative to existing text.
    `User-event`: `"LuasnipPreExpand"`
    `event_args`:
    - `expand_pos`: `{<row>, <column>}`, position at which the snippet will be
        expanded. `<row>` and `<column>` are both 0-indexed.
        `event_res`:
    - `env_override`: `map string->(string[]|string)`, override or extend the
        snippet’s environment (`snip.env`).

A pretty useless, beyond serving as an example here, application of these would
be printing e.g. the node’s text after entering:

>lua
    vim.api.nvim_create_autocmd("User", {
        pattern = "LuasnipInsertNodeEnter",
        callback = function()
            local node = require("luasnip").session.event_node
            print(table.concat(node:get_text(), "\n"))
        end
    })
<

or some information about expansions:

>lua
    vim.api.nvim_create_autocmd("User", {
        pattern = "LuasnipPreExpand",
        callback = function()
            -- get event-parameters from `session`.
            local snippet = require("luasnip").session.event_node
            local expand_position =
                require("luasnip").session.event_args.expand_pos
    
            print(string.format("expanding snippet %s at %s:%s",
                table.concat(snippet:get_docstring(), "\n"),
                expand_position[1],
                expand_position[2]
            ))
        end
    })
<


==============================================================================
26. Cleanup                                                  *luasnip-cleanup*

The function ls.cleanup() triggers the `LuasnipCleanup` user event, that you
can listen to do some kind of cleaning in your own snippets; by default it will
empty the snippets table and the caches of the lazy_load.


==============================================================================
27. Logging                                                  *luasnip-logging*

Luasnip uses logging to report unexpected program states, and information on
what’s going on in general. If something does not work as expected, taking a
look at the log (and potentially increasing the loglevel) might give some good
hints towards what is going wrong.

The log is stored in `<vim.fn.stdpath("log")>/luasnip.log`
(`<vim.fn.stdpath("cache")>/luasnip.log` for Neovim versions where
`stdpath("log")` does not exist), and can be opened by calling `ls.log.open()`.
The loglevel (granularity of reported events) can be adjusted by calling
`ls.log.set_loglevel("error"|"warn"|"info"|"debug")`. `"debug"` has the highest
granularity, `"error"` the lowest, the default is `"warn"`.

Once this log grows too large (10MiB, currently not adjustable), it will be
renamed to `luasnip.log.old`, and a new, empty log created in its place. If
there already exists a `luasnip.log.old`, it will be deleted.

`ls.log.ping()` can be used to verify the log is working correctly: it will
print a short message to the log.


==============================================================================
28. Source                                                    *luasnip-source*

It is possible to attach, to a snippet, information about its source. This can
be done either by the various loaders (if it is enabled in `ls.setup`
(|luasnip-config-options|, `loaders_store_source`)), or manually. The attached
data can be used by |luasnip-extras-snippet-location| to jump to the definition
of a snippet.

It is also possible to get/set the source of a snippet via API:

`ls.snippet_source`:

- `get(snippet) -> source_data`:
    Retrieve the source-data of `snippet`. `source_data` always contains the key
    `file`, the file in which the snippet was defined, and may additionally
    contain `line` or `line_end`, the first and last line of the definition.
- `set(snippet, source)`:
    Set the source of a snippet.
    - `snippet`: a snippet which was added via `ls.add_snippets`.
    - `source`: a `source`-object, obtained from either `from_debuginfo` or
        `from_location`.
- `from_location(file, opts) -> source`:
    - `file`: `string`, The path to the file in which the snippet is defined.
    - `opts`: `table|nil`, optional parameters for the source.
        - `line`: `number`, the first line of the definition. 1-indexed.
        - `line_end`: `number`, the final line of the definition. 1-indexed.
- `from_debuginfo(debuginfo) -> source`:
    Generates source from the table returned by `debug.getinfo` (from now on
    referred to as `debuginfo`). `debuginfo` has to be of a frame of a function
    which is backed by a file, and has to contain this information, ie. has to be
    generated by `debug.get_info(*, "Sl")` (at least `"Sl"`, it may also contain
    more info).


==============================================================================
29. Config-Options                                    *luasnip-config-options*

These are the settings you can provide to `luasnip.setup()`:

- `keep_roots`: Whether snippet-roots should be linked. See
    |luasnip-basics-snippet-insertion| for more context.
- `link_roots`: Whether snippet-roots should be linked. See
    |luasnip-basics-snippet-insertion| for more context.
- `exit_roots`: Whether snippet-roots should exit at reaching at their last node,
    `$0`. This setting is only valid for root snippets, not child snippets. This
    setting may avoid unexpected behavior by disallowing to jump earlier (finished)
    snippets. Check |luasnip-basics-snippet-insertion| for more information on
    snippet-roots.
- `link_children`: Whether children should be linked. See
    |luasnip-basics-snippet-insertion| for more context.
- `history` (deprecated): if not nil, `keep_roots`, `link_roots`, and
    `link_children` will be set to the value of `history`, and `exit_roots` will
    set to inverse value of `history`. This is just to ensure
    backwards-compatibility.
- `update_events`: Choose which events trigger an update of the active nodes’
    dependents. Default is just `'InsertLeave'`, `'TextChanged,TextChangedI'` would
    update on every change. These, like all other `*_events` are passed to
    `nvim_create_autocmd` as `events`, so they can be wrapped in a table, like
    >lua
        ls.setup({
          update_events = {"TextChanged", "TextChangedI"}
        })
    <
- `region_check_events`: Events on which to leave the current snippet-root if the
    cursor is outside its’ 'region'. Disabled by default, `'CursorMoved'`,
    `'CursorHold'` or `'InsertEnter'` seem reasonable.
- `delete_check_events`: When to check if the current snippet was deleted, and if
    so, remove it from the history. Off by default, `'TextChanged'` (perhaps
    `'InsertLeave'`, to react to changes done in Insert mode) should work just fine
    (alternatively, this can also be mapped using `<Plug>luasnip-delete-check`).
- `store_selection_keys`: Mapping for populating `TM_SELECTED_TEXT` and related
    variables (not set by default). If you want to set this mapping yourself, map
    `ls.select_keys` (not a function, actually a string/key-combination) as a rhs.
- `enable_autosnippets`: Autosnippets are disabled by default to minimize
    performance penalty if unused. Set to `true` to enable.
- `ext_opts`: Additional options passed to extmarks. Can be used to add
    passive/active highlight on a per-node-basis (more info in DOC.md)
- `parser_nested_assembler`: Override the default behaviour of inserting a
    `choiceNode` containing the nested snippet and an empty `insertNode` for nested
    placeholders (`"${1: ${2: this is nested}}"`). For an example (behaviour more
    similar to vscode), check here
    <https://github.com/L3MON4D3/LuaSnip/wiki/Nice-Configs#imitate-vscodes-behaviour-for-nested-placeholders>
- `ft_func`: Source of possible filetypes for snippets. Defaults to a function,
    which returns `vim.split(vim.bo.filetype, ".", true)`, but check
    filetype_functions <lua/luasnip/extras/filetype_functions.lua> or the
    |luasnip-extras-filetype-functions|-section for more options.
- `load_ft_func`: Function to determine which filetypes belong to a given buffer
    (used for `lazy_loading`). `fn(bufnr) -> filetypes (string[])`. Again, there
    are some examples in filetype_functions
    <lua/luasnip/extras/filetype_functions.lua>.
- `snip_env`: The best way to author snippets in lua involves the lua-loader (see
    |luasnip-loaders-lua|). Unfortunately, this requires that snippets are defined
    in separate files, which means that common definitions like `s`, `i`, `sn`,
    `t`, `fmt`, … have to be repeated in each of them, and that adding more
    customized functions to ease writing snippets also requires some setup.
    `snip_env` can be used to insert variables into exactly the places where
    lua-snippets are defined (for now only the file loaded by the lua-loader).
    Setting `snip_env` to `{ some_global = "a value" }` will add (amongst the
    defaults stated at the beginning of this documentation) the global variable
    `some_global` while evaluating these files. There are special keys which, when
    set in `snip_env` change the behaviour of this option, and are not passed
    through to the lua-files:
    - `__snip_env_behaviour`, string: either `"set"` or `"extend"` (default
        `"extend"`)
        If this is `"extend"`, the variables defined in `snip_env` will complement (and
        override) the defaults. If this is not desired, `"set"` will not include the
        defaults, but only the variables set here.
    One side-effect of this is that analysis-tools (most likely
    `lua-language-server`) for lua will generate diagnostics for the usage of
    undefined symbols. If you mind the (probably) large number of generated
    warnings, consider adding the undefined globals to the globals recognized by
    `lua-language-server` or add `---@diagnostic disable: undefined-global`
    somewhere in the affected files.
- `loaders_store_source`, boolean, whether loaders should store the source of the
    loaded snippets. Enabling this means that the definition of any snippet can be
    jumped to via |luasnip-extras-snippet-location|, but also entails slightly
    increased memory consumption (and load-time, but it’s not really noticeable).


==============================================================================
30. Troubleshooting                                  *luasnip-troubleshooting*


ADDING SNIPPETS                      *luasnip-troubleshooting-adding-snippets*

### Loaders

- **Filetypes**. LuaSnip uses `all` as the global filetype. As most snippet
    collections don’t explicitly target LuaSnip, they may not provide global
    snippets for this filetype, but another, like `_` (`honza/vim-snippets`). In
    these cases, it’s necessary to extend LuaSnip’s global filetype with the
    collection’s global filetype:
    >lua
        ls.filetype_extend("all", { "_" })
    <
    In general, if some snippets don’t show up when loading a collection, a good
    first step is checking the filetype LuaSnip is actually looking into (print
    them for the current buffer via `:lua
    print(vim.inspect(require("luasnip").get_snippet_filetypes()))`), against the
    one the missing snippet is provided for (in the collection). If there is indeed
    a mismatch, `filetype_extend` can be used to also search the collection’s
    filetype:
    >lua
        ls.filetype_extend("<luasnip-filetype>", { "<collection-filetype>" })
    <
- **Non-default ft_func loading**. As we only load `lazy_load`ed snippets on some
    events, `lazy_load` will probably not play nice when a non-default `ft_func` is
    used: if it depends on e.g. the cursor position, only the filetypes for the
    cursor position when the `lazy_load` events are triggered will be loaded. Check
    |luasnip-extras-filetype-function|’s `extend_load_ft` for a solution.


GENERAL ~

- **Snippets sharing triggers**. If multiple snippets could be triggered at the
    current buffer-position, the snippet that was defined first in one’s
    configuration will be expanded first. As a small, real-world LaTeX math
    example, given the following two snippets with triggers `.ov` and `ov`:
    >lua
        postfix( -- Insert over-line command to text via post-fix
            { trig = ".ov", snippetType = "autosnippet" },
            {
                f(function(_, parent)
                    return "\\overline{" .. parent.snippet.env.POSTFIX_MATCH .. "}"
                end, {}),
            }
        ),
        s( -- Insert over-line command
            { trig = "ov", snippetType="autosnippet" },
            fmt(
                [[\overline{<>}]],
                { i(1) },
                { delimiters = "<>" }
            )
        ),
    <
    If one types `x` followed by `.ov`, the postfix snippet expands producing
    `\overline{x}`. However, if the `postfix` snippet above is defined _after_ the
    normal snippet `s`, then the same key press sequence produces `x.\overline{}`.
    This behaviour can be overridden by explicitly providing a priority to such
    snippets. For example, in the above code, if the `postfix` snippet was defined
    after the normal snippet `s`, then adding `priority=1001` to the `postfix`
    snippet will cause it to expand as if it were defined before the normal snippet
    `s`. Snippet `priority` is discussed in the Snippets section
    <https://github.com/L3MON4D3/LuaSnip/blob/master/DOC.md#snippets> of the
    documentation.


==============================================================================
31. API                                                          *luasnip-api*

`require("luasnip")`:

- `add_snippets(ft:string or nil, snippets:list or table, opts:table or nil)`:
    Makes `snippets` (list of snippets) available in `ft`. If `ft` is `nil`,
    `snippets` should be a table containing lists of snippets, the keys are
    corresponding filetypes. `opts` may contain the following keys:
    - `type`: type of `snippets`, `"snippets"` or `"autosnippets"` (ATTENTION:
        plural form used here). This serves as default value for the `snippetType`
        key of each snippet added by this call see |luasnip-snippets|.
    - `key`: Key that identifies snippets added via this call.
        If `add_snippets` is called with a key that was already used, the snippets
        from that previous call will be removed.
        This can be used to reload snippets: pass an unique key to each
        `add_snippets` and just redo the `add_snippets`-call when the snippets have
        changed.
    - `override_priority`: set priority for all snippets.
    - `default_priority`: set priority only for snippets without snippet priority.
- `clean_invalidated(opts: table or nil) -> bool`: clean invalidated snippets
    from internal snippet storage. Invalidated snippets are still stored; it might
    be useful to actually remove them as they still have to be iterated during
    expansion.
    `opts` may contain:
    - `inv_limit`: how many invalidated snippets are allowed. If the number of
        invalid snippets doesn’t exceed this threshold, they are not yet cleaned up.
        A small number of invalidated snippets (<100) probably doesn’t affect runtime
        at all, whereas recreating the internal snippet storage might.
- `get_id_snippet(id)`: returns snippet corresponding to id.
- `in_snippet()`: returns true if the cursor is inside the current snippet.
- `jumpable(direction)`: returns true if the current node has a next(`direction`
    = 1) or previous(`direction` = -1), e.g. whether it’s possible to jump
    forward or backward to another node.
- `jump(direction)`: returns true if the jump was successful.
- `expandable()`: true if a snippet can be expanded at the current cursor
    position.
- `expand(opts)`: expands the snippet at(before) the cursor. `opts` may contain:
    - `jump_into_func` passed through to `ls.snip_expand`, check its’ doc for a
        description.
- `expand_or_jumpable()`: returns `expandable() or jumpable(1)` (exists only
    because commonly, one key is used to both jump forward and expand).
- `expand_or_locally_jumpable()`: same as `expand_or_jumpable()` except jumpable
    is ignored if the cursor is not inside the current snippet.
- `locally_jumpable(direction)`: same as `jumpable()` except it is ignored if the
    cursor is not inside the current snippet.
- `expand_or_jump()`: returns true if jump/expand was succesful.
- `expand_auto()`: expands the autosnippets before the cursor (not necessary to
    call manually, will be called via autocmd if `enable_autosnippets` is set in
    the config).
- `snip_expand(snip, opts)`: expand `snip` at the current cursor position. `opts`
    may contain the following keys:
    - `clear_region`: A region of text to clear after expanding (but before jumping
        into) snip. It has to be at this point (and therefore passed to this function)
        as clearing before expansion will populate `TM_CURRENT_LINE` and
        `TM_CURRENT_WORD` with wrong values (they would miss the snippet trigger) and
        clearing after expansion may move the text currently under the cursor and have
        it end up not at the `i(1)`, but a `#trigger` chars to its right. The actual
        values used for clearing are `from` and `to`, both (0,0)-indexed
        byte-positions. If the variables don’t have to be populated with the correct
        values, it’s safe to remove the text manually.
    - `expand_params`: table, override `trigger`, `captures` or environment of the
        snippet. This is useful for manually expanding snippets where the trigger
        passed via `trig` is not the text triggering the snippet, or those which expect
        `captures` (basically, snippets with a non-plaintext `trigEngine`).
        One example: ```lua snip_expand(snip, { trigger = "override_trigger", captures
        = {"first capture", "second capture"}, env_override = { this_key = "some
        value", other_key = {"multiple", "lines"}, TM_FILENAME =
        "some_other_filename.lua" } })
    - `pos`: position (`{line, col}`), (0,0)-indexed (in bytes, as returned by
        `nvim_win_get_cursor()`), where the snippet should be expanded. The snippet
        will be put between `(line,col-1)` and `(line,col)`. The snippet will be
        expanded at the current cursor if pos is nil.
    - `jump_into_func`: fn(snippet) -> node: Callback responsible for jumping into
        the snippet. The returned node is set as the new active node, ie. it is the
        origin of the next jump. The default is basically this: `lua function(snip) --
        jump_into set the placeholder of the snippet, 1 -- to jump forwards. return
        snip:jump_into(1)` while this can be used to only insert the snippet: `lua
        function(snip) return snip.insert_nodes[0] end`
    - `indent`: bool?, defaults to `true`. Whether LuaSnip will try to add additional
        indents to fit current indent level in snippet expanding. This option is useful
        when some LSP server already take indents into consideration. In such cases,
        LuaSnip should not try to add additional indents. If you are using `nvim-cmp`,
        sample config:
        >lua
            require("cmp").setup {
              snippet = {
                expand = function(args)
                  local indent_nodes = true
                  if vim.api.nvim_get_option_value("filetype", { buf = 0 }) == "dart" then
                    indent_nodes = false
                  end
                  require("luasnip").lsp_expand(args.body, {
                    indent = indent_nodes,
                  })
                end,
              },
            }
        <
    `opts` and any of its parameters may be nil.
- `get_active_snip()`: returns the currently active snippet (not node!).
- `choice_active()`: true if inside a choiceNode.
- `change_choice(direction)`: changes the choice in the innermost currently
    active choiceNode forward (`direction` = 1) or backward (`direction` = -1).
- `unlink_current()`: removes the current snippet from the jumplist (useful if
    luasnip fails to automatically detect e.g. deletion of a snippet) and sets the
    current node behind the snippet, or, if not possible, before it.
- `lsp_expand(snip_string, opts)`: expands the LSP snippet defined via
    `snip_string` at the cursor. `opts` can have the same options as `opts` in
    `snip_expand`.
- `active_update_dependents()`: update all function/dynamicNodes that have the
    current node as an argnode (will actually only update them if the text in any
    of the argnodes changed).
- `available(snip_info)`: returns a table of all snippets defined for the current
    filetypes(s) (`{ft1={snip1, snip2}, ft2={snip3, snip4}}`). The structure of the
    snippet is defined by `snip_info` which is a function (`snip_info(snip)`) that
    takes in a snippet (`snip`), finds the desired information on it, and returns
    it. `snip_info` is an optional argument as a default has already been defined.
    You can use it for more granular control over the table of snippets that is
    returned.
- `exit_out_of_region(node)`: checks whether the cursor is still within the range
    of the root-snippet `node` belongs to. If yes, no change occurs; if no, the
    root-snippet is exited and its `$0` will be the new active node. If a jump
    causes an error (happens mostly because the text of a snippet was deleted), the
    snippet is removed from the jumplist and the current node set to the
    end/beginning of the next/previous snippet.
- `store_snippet_docstrings(snippet_table)`: Stores the docstrings of all
    snippets in `snippet_table` to a file
    (`stdpath("cache")/luasnip/docstrings.json`). Calling
    `store_snippet_docstrings(snippet_table)` after adding/modifying snippets and
    `load_snippet_docstrings(snippet_table)` on startup after all snippets have
    been added to `snippet_table` is a way to avoide regenerating the (unchanged)
    docstrings on each startup. (Depending on when the docstrings are required and
    how luasnip is loaded, it may be more sensible to let them load lazily,
    e.g. just before they are required). `snippet_table` should be laid out just
    like `luasnip.snippets` (it will most likely always _be_ `luasnip.snippets`).
- `load_snippet_docstrings(snippet_table)`: Load docstrings for all snippets in
    `snippet_table` from `stdpath("cache")/luasnip/docstrings.json`. The docstrings
    are stored and restored via trigger, meaning if two snippets for one filetype
    have the same (very unlikely to happen in actual usage), bugs could occur.
    `snippet_table` should be laid out as described in `store_snippet_docstrings`.
- `unlink_current_if_deleted()`: Checks if the current snippet was deleted; if
    so, it is removed from the jumplist. This is not 100% reliable as LuaSnip only
    sees the extmarks and their beginning/end may not be on the same position, even
    if all the text between them was deleted.
- `filetype_extend(filetype:string, extend_filetypes:table of string)`: Tells
    luasnip that for a buffer with `ft=filetype`, snippets from `extend_filetypes`
    should be searched as well. `extend_filetypes` is a lua-array (`{ft1, ft2,
    ft3}`). `luasnip.filetype_extend("lua", {"c", "cpp"})` would search and expand
    c and cpp snippets for lua files.
- `filetype_set(filetype:string, replace_filetypes:table of string)`: Similar to
    `filetype_extend`, but where _append_ appended filetypes, _set_ sets them:
    `filetype_set("lua", {"c"})` causes only c snippets to be expanded in lua
    files; lua snippets aren’t even searched.
- `cleanup()`: clears all snippets. Not useful for regular usage, only when
    authoring and testing snippets.
- `refresh_notify(ft:string)`: Triggers an autocmd that other plugins can hook
    into to perform various cleanup for the refreshed filetype. Useful for
    signaling that new snippets were added for the filetype `ft`.
- `set_choice(indx:number)`: Changes to the `indx`th choice. If no `choiceNode`
    is active, an error is thrown. If the active `choiceNode` doesn’t have an
    `indx`th choice, an error is thrown.
- `get_current_choices() -> string[]`: Returns a list of multiline-strings
    (themselves lists, even if they have only one line), the `i`th string
    corresponding to the `i`th choice of the currently active `choiceNode`. If no
    `choiceNode` is active, an error is thrown.
- `setup_snip_env()`: Adds the variables defined (during `setup`) in `snip_env`
    to the callers environment.
- `get_snip_env()`: Returns `snip_env`.
- `jump_destination(direction)`: Returns the node the next jump in `direction`
    (either -1 or 1, for backwards, forwards respectively) leads to, or `nil` if
    the destination could not be determined (most likely because there is no node
    that can be jumped to in the given direction, or there is no active node).
- `activate_node(opts)`: Activate a node in any snippet. `opts` contains the
    following options:
    - `pos`, `{[1]: row, [2]: byte-column}?`: The position at which a node should
        be activated. Defaults to the position of the cursor.
    - `strict`, `bool?`: If set, throw an error if the node under the cursor can’t
        be jumped into. If not set, fall back to any node of the snippet and enter
        that instead.
    - `select`, `bool?`: Whether the text inside the node should be selected.
        Defaults to true.

Not covered in this section are the various node-constructors exposed by the
module, their usage is shown either previously in this file or in
`Examples/snippets.lua` (in the repo).

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