modules/lsp/server: declare package defaults

Convert the `attrsOf (servers.nix)` option to a freeform submodule.

Declare a `servers.nix` option for each lsp server listed in
`lsp-packages.nix` that has a known nixpkgs package.

modules/lsp/default.nix

@@ -2,6 +2,7 @@
   lib,
   config,
   options,
+  pkgs,
   ...
 }:
 let
@@ -9,6 +10,55 @@ let
   inherit (lib.nixvim) toLuaObject;
 
   cfg = config.lsp;
+
+  # Import `server.nix` and apply args
+  # For convenience, we set a default here for args.pkgs
+  mkServerModule = args: lib.modules.importApply ./server.nix ({ inherit pkgs; } // args);
+
+  # Create a submodule type from `server.nix`
+  # Used as the type for both the freeform `lsp.servers.<name>`
+  # and the explicitly declared `lsp.servers.*` options
+  mkServerType = args: types.submodule (mkServerModule args);
+
+  # Create a server option
+  # Used below for the `lsp.servers.*` options
+  mkServerOption =
+    name: args:
+    let
+      homepage = lib.pipe options.lsp.servers [
+        # Get suboptions of `lsp.servers`
+        (opt: opt.type.getSubOptions opt.loc)
+        # Get suboptions of `lsp.servers.<name>`
+        (opts: opts.${name}.type.getSubOptions opts.${name}.loc)
+        # Get package option's homepage
+        (opts: opts.package.default.meta.homepage or null)
+      ];
+
+      # If there's a known homepage for this language server,
+      # we'll link to it in the option description
+      nameLink = if homepage == null then name else "[${name}](${homepage})";
+    in
+    lib.mkOption {
+      type = mkServerType args;
+      description = ''
+        The ${nameLink} language server.
+      '';
+      default = { };
+    };
+
+  # Combine `packages` and `customCmd` sets from `lsp-packages.nix`
+  # We use this set to generate the package-option defaults
+  serverPackages =
+    let
+      inherit (import ../../plugins/lsp/lsp-packages.nix)
+        packages
+        customCmd
+        ;
+    in
+    builtins.mapAttrs (name: v: {
+      inherit name;
+      package = v.package or v;
+    }) (packages // customCmd);
 in
 {
   options.lsp = {
@@ -25,7 +75,11 @@ in
     };
 
     servers = lib.mkOption {
-      type = types.attrsOf (types.submodule ./server.nix);
+      type = types.submodule {
+        freeformType = types.attrsOf (mkServerType { });
+        options = builtins.mapAttrs mkServerOption serverPackages;
+      };
+
       description = ''
         LSP servers to enable and/or configure.
 
@@ -35,7 +89,7 @@ in
         This can be installed using [`${options.plugins.lspconfig.enable}`][`plugins.lspconfig`].
 
         [nvim-lspconfig]: ${options.plugins.lspconfig.package.default.meta.homepage}
-        [`plugins.lspconfig`]: ../plugins/lspconfig/index.md
+        [`plugins.lspconfig`]: ../../plugins/lspconfig/index.md
       '';
       default = { };
       example = {

modules/lsp/server.nix

@@ -1,59 +1,74 @@
+# Usage: lib.importApply ./server.nix { /*args*/ }
+{
+  name ? null,
+  package ? null,
+  # Avoid naming conflict with the `config` module arg
+  # TODO: consider renaming the `config` option to something like `settings`?
+  configOption ? null,
+  pkgs ? { },
+}@args:
 { lib, name, ... }:
 let
   inherit (lib) types;
+  displayName = args.name or "the language server";
+  packageName = package.name or (lib.strings.removePrefix "the " displayName);
 in
 {
   options = {
-    enable = lib.mkEnableOption "the language server";
+    enable = lib.mkEnableOption displayName;
 
     name = lib.mkOption {
       type = types.maybeRaw types.str;
       description = ''
-        The name of the language server, supplied to functions like `vim.lsp.enable()`.
+        The name to use for ${displayName}.
+        Supplied to functions like `vim.lsp.enable()`.
       '';
-      default = name;
-      defaultText = lib.literalMD "the attribute name";
+      # Use the supplied attr name, or fallback to the name module-arg
+      default = args.name or name;
+      defaultText = args.name or (lib.literalMD "the attribute name");
     };
 
     activate = lib.mkOption {
       type = types.bool;
       description = ''
-        Whether to call `vim.lsp.enable()` for this server.
+        Whether to call `vim.lsp.enable()` for ${displayName}.
       '';
       default = true;
       example = false;
     };
 
-    package = lib.mkOption {
-      type = with types; nullOr package;
-      default = null;
-      description = ''
-        Package to use for this language server.
+    package = lib.mkPackageOption pkgs packageName {
+      nullable = true;
+      default = package.default or package;
+      example = package.example or null;
+      extraDescription = ''
+        ${package.extraDescription or ""}
 
-        Alternatively, the language server should be available on your `$PATH`.
+        Alternatively, ${displayName} should be installed on your `$PATH`.
       '';
     };
 
     config = lib.mkOption {
       type = with types; attrsOf anything;
       description = ''
-        Configurations for each language server.
+        Configurations for ${displayName}. ${configOption.extraDescription or ""}
       '';
       default = { };
-      example = {
-        cmd = [
-          "clangd"
-          "--background-index"
-        ];
-        root_markers = [
-          "compile_commands.json"
-          "compile_flags.txt"
-        ];
-        filetypes = [
-          "c"
-          "cpp"
-        ];
-      };
+      example =
+        configOption.example or {
+          cmd = [
+            "clangd"
+            "--background-index"
+          ];
+          root_markers = [
+            "compile_commands.json"
+            "compile_flags.txt"
+          ];
+          filetypes = [
+            "c"
+            "cpp"
+          ];
+        };
     };
   };
 }