modules: add snippet backends

module-list.nix

@@ -18,6 +18,10 @@
   ./modules/plugins/navigation/hop-nvim.nix
   ./modules/plugins/navigation/telescope.nix
   ./modules/plugins/navigation/nvim-tree.nix
+  ./modules/plugins/snippet/luasnip.nix
+  ./modules/plugins/snippet/snippy.nix
+  ./modules/plugins/snippet/ultisnips.nix
+  ./modules/plugins/snippet/vsnip.nix
   ./modules/plugins/style/neoformat.nix
   ./modules/plugins/style/nvim-treesitter.nix
   ./modules/plugins/theme/catppuccin.nix

modules/plugins/nvim-cmp.nix

@@ -3,6 +3,8 @@
 let
   inherit (lib.nix2lua) pipe1 var call call0;
   cfg = config.plugins.nvim-cmp;
+
+  inherit (config.plugins) snippet language-server;
 in
 {
   options.plugins.nvim-cmp = with lib; {
@@ -16,33 +18,37 @@ in
     };
   };
 
+
   config = lib.mkIf cfg.enable (lib.mkMerge [
     {
-      plugin.luasnip = { };
-      plugin.cmp_luasnip = lib.mkDefault { isDependency = true; };
-
-      fn.nvim-cmp-snippet-expand = {
-        args = [ "args" ];
-        content = args: {
-          extra = pipe1
-            (var config.plugin.luasnip.varName)
-            (call "lsp_expand" args);
-        };
-      };
-
-      vim.opt.completeopt = [ "menu" "menuone" "noselect" ];
-
-      plugin.nvim-cmp = {
-        name = "cmp";
-        package = cfg.package;
-        setupSettings = lib.mkMerge [
-          cfg.settings
-          { snippet.expand = config.fn.nvim-cmp-snippet-expand.lambda; }
-        ];
-      };
+      assertions = [
+        {
+          assertion = snippet.luasnip.enable || snippet.snippy.enable || snippet.vsnip.enable || snippet.ultisnips.enable;
+          message = "One of snippet backend (luasnip, snippy, vsnip, ultisnip) is required to use nvim-cmp";
+        }
+      ];
     }
 
-    (lib.mkIf config.plugins.language-server.lspconfig.enable {
+    # Backend dependencies
+
+    (lib.mkIf snippet.luasnip.enable {
+      plugin.cmp_luasnip = {
+        isDependency = true;
+      };
+    })
+    (lib.mkIf snippet.snippy.enable {
+      plugin.cmp-snippy = { isDependency = true; };
+    })
+    (lib.mkIf snippet.vsnip.enable {
+      plugin.cmp-vsnip = { isDependency = true; };
+    })
+    (lib.mkIf snippet.ultisnips.enable {
+      plugin.cmp-nvim-ultisnips = { isDependency = true; };
+    })
+
+    # Lsp configuration
+
+    (lib.mkIf language-server.lspconfig.enable {
       plugin.cmp-nvim-lsp = {
         name = "cmp_nvim_lsp";
       };
@@ -52,6 +58,51 @@ in
           (var config.plugin.cmp-nvim-lsp.varName)
           (call0 "default_capabilities");
     })
+
+    # Base configuration
+
+    {
+      vim.opt.completeopt = [ "menu" "menuone" "noselect" ];
+
+      fn.nvim-cmp-snippet-expand = {
+        args = [ "args" ];
+        content = { args }:
+          let body = pipe1 args (var "body"); in {
+            extra =
+              if snippet.luasnip.enable then
+                pipe1 (var config.plugin.luasnip.varName) (call "lsp_expand" body)
+              else if snippet.vsnip.enable then
+                call "vim.fn[\"${config.plugin.vim-vsnip.name}#anonymous\"]" body
+              else if snippet.snippy.enable then
+                pipe1 (var config.plugin.nvim-snippy.varName) (call "expand_snipped" body)
+              else if snippet.ultisnips.enable then
+                call "vim.fn[\"${config.plugin.ultisnips.name}#Anon\"]" body
+              else
+                call "vim.snippet.expand" body; # For native neovim snippets (Neovim v0.10+);
+          };
+      };
+
+      plugin.nvim-cmp = rec {
+        name = "cmp";
+        varName = name;
+        package = cfg.package;
+        setupSettings = lib.mkMerge [
+          {
+            mapping = call0 "${varName}.mapping.preset.insert";
+            sources =
+              lib.optional language-server.lspconfig.enable { name = "nvim_lsp"; group_index = 1; }
+              ++ lib.optional snippet.luasnip.enable { name = "luasnip"; group_index = 5; }
+              ++ lib.optional snippet.snippy.enable { name = "snippy"; group_index = 5; }
+              ++ lib.optional snippet.vsnip.enable { name = "vsnip"; group_index = 5; }
+              ++ lib.optional snippet.ultisnips.enable { name = "ultisnips"; group_index = 5; }
+              ++ [{ name = "buffer"; group_index = 10; max_item_count = 10; }];
+          }
+          cfg.settings
+          { snippet.expand = config.fn.nvim-cmp-snippet-expand.lambda; }
+        ];
+      };
+    }
+
   ]);
 
 }

modules/plugins/snippet/luasnip.nix

@@ -0,0 +1,18 @@
+{ config, lib, pkgs, ... }:
+
+let
+  cfg = config.plugins.snippet.luasnip;
+in
+{
+  options.plugins.snippet.luasnip = with lib; {
+    enable = mkEnableOption "luasnip";
+
+    package = mkPackageOption pkgs.vimPlugins "luasnip" { };
+  };
+
+  config = lib.mkIf cfg.enable {
+    plugin.luasnip = {
+      inherit (cfg) package;
+    };
+  };
+}

modules/plugins/snippet/snippy.nix

@@ -0,0 +1,19 @@
+{ config, lib, pkgs, ... }:
+
+let
+  cfg = config.plugins.snippet.snippy;
+in
+{
+  options.plugins.snippet.snippy = with lib; {
+    enable = mkEnableOption "snippy";
+
+    package = mkPackageOption pkgs.vimPlugins "nvim-snippy" { };
+  };
+
+  config = lib.mkIf cfg.enable {
+    plugin.nvim-snippy = {
+      name = "snippy";
+      inherit (cfg) package;
+    };
+  };
+}

modules/plugins/snippet/ultisnips.nix

@@ -0,0 +1,20 @@
+{ config, lib, pkgs, ... }:
+
+let
+  cfg = config.plugins.snippet.ultisnips;
+in
+{
+  options.plugins.snippet.ultisnips = with lib; {
+    enable = mkEnableOption "ultisnips";
+
+    package = mkPackageOption pkgs.vimPlugins "ultisnips" { };
+  };
+
+  config = lib.mkIf cfg.enable {
+    plugin.ultisnips = {
+      inherit (cfg) package;
+      name = "UltiSnips";
+      isDependency = true;
+    };
+  };
+}

modules/plugins/snippet/vsnip.nix

@@ -0,0 +1,20 @@
+{ config, lib, pkgs, ... }:
+
+let
+  cfg = config.plugins.snippet.vsnip;
+in
+{
+  options.plugins.snippet.vsnip = with lib; {
+    enable = mkEnableOption "vsnip";
+
+    package = mkPackageOption pkgs.vimPlugins "vim-vsnip" { };
+  };
+
+  config = lib.mkIf cfg.enable {
+    plugin.vim-vsnip = {
+      inherit (cfg) package;
+      name = "vsnip";
+      isDependency = true;
+    };
+  };
+}

modules/profiles/recommended-plugins.nix

@@ -53,6 +53,8 @@ let inherit (lib.nix2lua) nf; in
       };
     };
 
+    snippet.luasnip.enable = lib.mkDefault true;
+
     style = {
       neoformat.enable = lib.mkDefault true;
       nvim-treesitter.enable = lib.mkDefault true;