plugins/none-ls: refactor using mkSourcePlugin

Introduce `_mk-source-plugin.nix`, which returns a module handling a
specific none-ls source plugin.

This wasn't possible previously due to IFD conflicting with evaluating
module imports.

Adjusted the test to use the `options` provided via module args, and
cleaned up some stuff allowing "unpackaged" sources to not be listed
again in the test file.

plugins/none-ls/_mk-source-plugin.nix

@@ -0,0 +1,58 @@
+# mkSourcePlugin, returns a module
+sourceType: sourceName:
+{
+  config,
+  pkgs,
+  lib,
+  helpers,
+  ...
+}:
+let
+  inherit (import ./packages.nix pkgs) packaged unpackaged;
+
+  cfg = config.plugins.none-ls;
+  cfg' = config.plugins.none-ls.sources.${sourceType}.${sourceName};
+in
+{
+  options.plugins.none-ls.sources.${sourceType}.${sourceName} =
+    {
+      enable = lib.mkEnableOption "the ${sourceName} ${sourceType} source for none-ls";
+      withArgs = helpers.mkNullOrOption helpers.nixvimTypes.strLua ''
+        Raw Lua code passed as an argument to the source's `with` method.
+      '';
+    }
+    # Only declare a package option if a package is required
+    // lib.optionalAttrs (packaged ? ${sourceName} || lib.elem sourceName unpackaged) {
+      package =
+        let
+          pkg = packaged.${sourceName} or null;
+        in
+        lib.mkOption (
+          {
+            type = lib.types.nullOr lib.types.package;
+            description =
+              "Package to use for ${sourceName}."
+              + (lib.optionalString (pkg == null) (
+                "\n\n"
+                + ''
+                  Currently not packaged in nixpkgs.
+                  Either set this to `null` and install ${sourceName} outside of nix,
+                  or set this to a custom nix package.
+                ''
+              ));
+          }
+          // lib.optionalAttrs (pkg != null) { default = pkg; }
+        );
+    };
+
+  config = lib.mkIf (cfg.enable && cfg'.enable) {
+    plugins.none-ls.settings.sources = lib.mkDefault [
+      (
+        "require('null-ls').builtins.${sourceType}.${sourceName}"
+        + lib.optionalString (cfg'.withArgs != null) ".with(${cfg'.withArgs})"
+      )
+    ];
+
+    extraPackages = [ (cfg'.package or null) ];
+  };
+}

plugins/none-ls/servers.nix

@@ -1,82 +1,22 @@
-{
-  pkgs,
-  config,
-  lib,
-  helpers,
-  ...
-}:
+{ config, lib, ... }:
 let
   noneLsBuiltins = import ../../generated/none-ls.nix;
-
-  inherit (import ./packages.nix pkgs) packaged unpackaged;
-
-  # Does this builitin require a package ?
-  builitinNeedsPackage = source: lib.hasAttr source packaged || lib.elem source unpackaged;
+  mkSourcePlugin = import ./_mk-source-plugin.nix;
 in
 {
-  imports = [ ./prettier.nix ];
-
-  options.plugins.none-ls.sources = lib.mapAttrs (
-    sourceType: sources:
-    lib.listToAttrs (
-      lib.map (source: {
-        name = source;
-        value =
-          {
-            enable = lib.mkEnableOption "the ${source} ${sourceType} source for none-ls";
-            withArgs = helpers.mkNullOrOption helpers.nixvimTypes.strLua ''
-              Raw Lua code passed as an argument to the source's `with` method.
-            '';
-          }
-          // lib.optionalAttrs (builitinNeedsPackage source) {
-            package =
-              let
-                pkg = packaged.${source} or null;
-              in
-              lib.mkOption (
-                {
-                  type = lib.types.nullOr lib.types.package;
-                  description =
-                    "Package to use for ${source} by none-ls. "
-                    + (lib.optionalString (pkg == null) ''
-                      Not handled in nixvim, either install externally and set to null or set the option with a derivation.
-                    '');
-                }
-                // lib.optionalAttrs (pkg != null) { default = pkg; }
-              );
-          };
-      }) sources
-    )
-  ) noneLsBuiltins;
+  imports =
+    [ ./prettier.nix ]
+    ++ (lib.flatten (
+      lib.mapAttrsToList (category: (lib.map (mkSourcePlugin category))) noneLsBuiltins
+    ));
 
   config =
     let
       cfg = config.plugins.none-ls;
       gitsignsEnabled = cfg.sources.code_actions.gitsigns.enable;
-
-      flattenedSources = lib.flatten (
-        lib.mapAttrsToList (
-          sourceType: sources:
-          (lib.mapAttrsToList (sourceName: source: source // { inherit sourceType sourceName; }) sources)
-        ) cfg.sources
-      );
-
-      enabledSources = builtins.filter (source: source.enable) flattenedSources;
     in
     lib.mkIf cfg.enable {
-      plugins.none-ls.settings.sources = lib.mkIf (enabledSources != [ ]) (
-        map (
-          {
-            sourceType,
-            sourceName,
-            withArgs,
-            ...
-          }:
-          "require('null-ls').builtins.${sourceType}.${sourceName}"
-          + lib.optionalString (withArgs != null) ".with(${withArgs})"
-        ) enabledSources
-      );
+      # Enable gitsigns if the gitsigns source is enabled
       plugins.gitsigns.enable = lib.mkIf gitsignsEnabled true;
-      extraPackages = map (source: source.package or null) enabledSources;
     };
 }