R: adding LSP (#378)

* r: implementing lsp

* r: version bump to context fixes treesitter bug

* r: changing treesitter package definition to mkGrammarOption

* added changelog entry

* docs: wording

---------

Co-authored-by: raf <raf@notashelf.dev>

modules/plugins/languages/default.nix

@@ -17,6 +17,7 @@ in {
     ./ocaml.nix
     ./php.nix
     ./python.nix
+    ./r.nix
     ./rust.nix
     ./sql.nix
     ./svelte.nix

modules/plugins/languages/r.nix

@@ -0,0 +1,78 @@
+{
+  config,
+  pkgs,
+  lib,
+  ...
+}: let
+  inherit (builtins) attrNames;
+  inherit (lib.options) mkEnableOption mkOption literalExpression;
+  inherit (lib.modules) mkIf mkMerge;
+  inherit (lib.lists) isList;
+  inherit (lib.types) enum either listOf package str;
+  inherit (lib.nvim.lua) expToLua;
+  inherit (lib.nvim.types) mkGrammarOption;
+
+  cfg = config.vim.languages.r;
+
+  r-with-languageserver = pkgs.rWrapper.override {
+    packages = with pkgs.rPackages; [languageserver];
+  };
+
+  defaultServer = "r_language_server";
+  servers = {
+    r_language_server = {
+      package = pkgs.writeShellScriptBin "r_lsp" ''
+        ${r-with-languageserver}/bin/R --slave -e "languageserver::run()"
+      '';
+      lspConfig = ''
+        lspconfig.r_language_server.setup{
+          capabilities = capabilities;
+          on_attach = default_on_attach;
+          cmd = ${
+          if isList cfg.lsp.package
+          then expToLua cfg.lsp.package
+          else ''{"${lib.getExe cfg.lsp.package}"}''
+        }
+        }
+      '';
+    };
+  };
+in {
+  options.vim.languages.r = {
+    enable = mkEnableOption "R language support";
+
+    treesitter = {
+      enable = mkEnableOption "R treesitter" // {default = config.vim.languages.enableTreesitter;};
+      package = mkGrammarOption pkgs "r";
+    };
+
+    lsp = {
+      enable = mkEnableOption "R LSP support" // {default = config.vim.languages.enableLSP;};
+
+      server = mkOption {
+        description = "R LSP server to use";
+        type = enum (attrNames servers);
+        default = defaultServer;
+      };
+
+      package = mkOption {
+        description = "R LSP server package, or the command to run as a list of strings";
+        example = literalExpression "[ (lib.getExe pkgs.jdt-language-server) \"-data\" \"~/.cache/jdtls/workspace\" ]";
+        type = either package (listOf str);
+        default = servers.${cfg.lsp.server}.package;
+      };
+    };
+  };
+
+  config = mkIf cfg.enable (mkMerge [
+    (mkIf cfg.treesitter.enable {
+      vim.treesitter.enable = true;
+      vim.treesitter.grammars = [cfg.treesitter.package];
+    })
+
+    (mkIf cfg.lsp.enable {
+      vim.lsp.lspconfig.enable = true;
+      vim.lsp.lspconfig.sources.r-lsp = servers.${cfg.lsp.server}.lspConfig;
+    })
+  ]);
+}