programs.neovim: init (#98506)

* programs.neovim: init

Allows to build a proper runtime folder with after/ ftplugin/ parser/ subfolders etc.
(neo)vim expects a few different folders, for instance to load
treesitter parsers.

This PR reuses the builder from the etc module, notwithstanding the
different modes/uid/gid.

This allows to get rid of some autocmd in customRC (via proper use of
the folder hierarchy) which is a win in my opinion.

nixos/modules/module-list.nix

@@ -140,6 +140,7 @@
   ./programs/mininet.nix
   ./programs/mtr.nix
   ./programs/nano.nix
+  ./programs/neovim.nix
   ./programs/nm-applet.nix
   ./programs/npm.nix
   ./programs/oblogout.nix

nixos/modules/programs/neovim.nix

@@ -0,0 +1,165 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+  cfg = config.programs.neovim;
+
+  runtime' = filter (f: f.enable) (attrValues cfg.runtime);
+
+  # taken from the etc module
+  runtime = pkgs.stdenvNoCC.mkDerivation {
+    name = "runtime";
+
+    builder = ../system/etc/make-etc.sh;
+
+    preferLocalBuild = true;
+    allowSubstitutes = false;
+
+    sources = map (x: x.source) runtime';
+    targets = map (x: x.target) runtime';
+  };
+
+in {
+  options.programs.neovim = {
+    enable = mkEnableOption "Neovim";
+
+    defaultEditor = mkOption {
+      type = types.bool;
+      default = false;
+      description = ''
+        When enabled, installs neovim and configures neovim to be the default editor
+        using the EDITOR environment variable.
+      '';
+    };
+
+    viAlias = mkOption {
+      type = types.bool;
+      default = false;
+      description = ''
+        Symlink <command>vi</command> to <command>nvim</command> binary.
+      '';
+    };
+
+    vimAlias = mkOption {
+      type = types.bool;
+      default = false;
+      description = ''
+        Symlink <command>vim</command> to <command>nvim</command> binary.
+      '';
+    };
+
+    withRuby = mkOption {
+      type = types.bool;
+      default = true;
+      description = "Enable ruby provider.";
+    };
+
+    configure = mkOption {
+      type = types.attrs;
+      default = {};
+      example = literalExample ''
+        configure = {
+            customRC = $''''
+            " here your custom configuration goes!
+            $'''';
+            packages.myVimPackage = with pkgs.vimPlugins; {
+              # loaded on launch
+              start = [ fugitive ];
+              # manually loadable by calling `:packadd $plugin-name`
+              opt = [ ];
+            };
+          };
+      '';
+      description = ''
+        Generate your init file from your list of plugins and custom commands.
+        Neovim will then be wrapped to load <command>nvim -u /nix/store/<hash>-vimrc</command>
+      '';
+    };
+
+    package = mkOption {
+      type = types.package;
+      default = pkgs.neovim-unwrapped;
+      defaultText = literalExample "pkgs.neovim-unwrapped";
+      description = "The package to use for the neovim binary.";
+    };
+
+    finalPackage = mkOption {
+      type = types.package;
+      visible = false;
+      readOnly = true;
+      description = "Resulting customized neovim package.";
+    };
+
+    runtime = mkOption {
+      default = {};
+      example = literalExample ''
+        runtime."ftplugin/c.vim".text = "setlocal omnifunc=v:lua.vim.lsp.omnifunc";
+      '';
+      description = ''
+        Set of files that have to be linked in <filename>runtime</filename>.
+      '';
+
+      type = with types; attrsOf (submodule (
+        { name, config, ... }:
+        { options = {
+
+            enable = mkOption {
+              type = types.bool;
+              default = true;
+              description = ''
+                Whether this /etc file should be generated.  This
+                option allows specific /etc files to be disabled.
+              '';
+            };
+
+            target = mkOption {
+              type = types.str;
+              description = ''
+                Name of symlink.  Defaults to the attribute
+                name.
+              '';
+            };
+
+            text = mkOption {
+              default = null;
+              type = types.nullOr types.lines;
+              description = "Text of the file.";
+            };
+
+            source = mkOption {
+              type = types.path;
+              description = "Path of the source file.";
+            };
+
+          };
+
+          config = {
+            target = mkDefault name;
+            source = mkIf (config.text != null) (
+              let name' = "neovim-runtime" + baseNameOf name;
+              in mkDefault (pkgs.writeText name' config.text));
+          };
+
+        }));
+
+    };
+  };
+
+  config = mkIf cfg.enable {
+    environment.systemPackages = [
+      cfg.finalPackage
+    ];
+    environment.variables = { EDITOR = mkOverride 900 "nvim"; };
+
+    programs.neovim.finalPackage = pkgs.wrapNeovim cfg.package {
+      inherit (cfg) viAlias vimAlias;
+      configure = cfg.configure // {
+
+        customRC = (cfg.configure.customRC or "") + ''
+          set runtimepath^=${runtime}/etc
+        '';
+      };
+    };
+  };
+}