Add flake

flake.nix

@@ -0,0 +1,114 @@
+rec {
+  description = "";
+
+  inputs = {
+    nixpkgs.url = "nixpkgs"; # Use nixpkgs from system registry
+    flake-utils.url = "github:numtide/flake-utils";
+  };
+
+  outputs = {
+    self,
+    nixpkgs,
+    flake-utils,
+  }:
+  # Create a shell (and possibly package) for each possible system, not only x86_64-linux
+    flake-utils.lib.eachDefaultSystem (system: let
+      # =========================================================================================
+      # Define pkgs/stdenvs
+      # =========================================================================================
+      pkgs = import nixpkgs {
+        inherit system;
+        config.allowUnfree = true;
+        overlays = [];
+      };
+
+      inherit (pkgs) lib stdenv;
+
+      # =========================================================================================
+      # Define shell environment
+      # =========================================================================================
+
+      # Setup the shell when entering the "nix develop" environment (bash script).
+      shellHook = let
+        # Add project-local fish abbrs here
+        abbrs = {};
+
+        eraseAbbr = name: value: ''abbr --erase ${name} 2>/dev/null'';
+        createAbbr = name: value: ''abbr -a ${name} "${value}"'';
+
+        # This will be sourced by the global fish config if INIT_PROJECT_SHELL gets unset
+        unloadProjectShell = pkgs.writers.writeFish "unload-shell.fish" ''
+          echo "Unloading \"${description}\" environment..."
+
+          ${builtins.concatStringsSep "\n" (lib.mapAttrsToList eraseAbbr abbrs)}
+        '';
+
+        # This will be sourced by the global fish config if INIT_PROJECT_SHELL gets set
+        initProjectShell = pkgs.writers.writeFish "init-shell.fish" ''
+          # Unload just in case, to not have redefinition errors
+          source ${unloadProjectShell}
+
+          echo "Sourcing \"${description}\" environment..."
+
+          ${builtins.concatStringsSep "\n" (lib.mapAttrsToList createAbbr abbrs)}
+        '';
+      in
+        builtins.concatStringsSep "\n" [
+          # Launch into pure fish shell
+          ''
+            # Determine the project root, used e.g. in cmake scripts
+            export FLAKE_PROJECT_ROOT="$(git rev-parse --show-toplevel)"
+
+            # Can't do the "exec" with nix-direnv
+            # - The "exec fish" would call direnv again => Infinite loop
+            # - The shellHook is Bash/POSIX, so fish syntax doesn't work
+
+            # Use this for "nix develop" without direnv
+            # exec "$(type -p fish)" -C "source ${initProjectShell} && abbr -a menu '${pkgs.bat}/bin/bat "${initProjectShell}"'"
+
+            # Use this for direnv without "nix develop"
+            export INIT_PROJECT_SHELL="${initProjectShell}"
+            export UNLOAD_PROJECT_SHELL="${unloadProjectShell}"
+          ''
+        ];
+
+      # ===========================================================================================
+      # Define custom dependencies
+      # ===========================================================================================
+
+      # ===========================================================================================
+      # Specify dependencies
+      # https://nixos.org/manual/nixpkgs/stable/#ssec-stdenv-dependencies-overview
+      # Just for a "nix develop" shell, buildInputs can be used for everything.
+      # ===========================================================================================
+
+      # Add dependencies to nativeBuildInputs if they are executed during the build:
+      # - Those which are needed on $PATH during the build, for example cmake and pkg-config
+      # - Setup hooks, for example makeWrapper
+      # - Interpreters needed by patchShebangs for build scripts (with the --build flag), which can be the case for e.g. perl
+      nativeBuildInputs = with pkgs; [];
+
+      # Add dependencies to buildInputs if they will end up copied or linked into the final output or otherwise used at runtime:
+      # - Libraries used by compilers, for example zlib
+      # - Interpreters needed by patchShebangs for scripts which are installed, which can be the case for e.g. perl
+      buildInputs = with pkgs; [];
+      # ===========================================================================================
+      # Define buildable + installable packages
+      # ===========================================================================================
+    in rec {
+      devShells = {
+        # Provide default environment for "nix develop".
+        # Other environments can be added below.
+        default = pkgs.mkShell {
+          inherit nativeBuildInputs buildInputs shellHook;
+          name = description;
+
+          # =========================================================================================
+          # Define environment variables
+          # =========================================================================================
+
+          BIBINPUTS = "$PWD:$BIBINPUTS";
+        };
+      };
+    });
+}