lib/neovim-plugin: Add lua configuration scoped to the plugin

This commit adds a `plugins.<name>.luaConfig` section controlling the
plugin specific configuration.

The section contains the internal `init` option, containing the plugin's
initialization code.

It also contains the public `pre` and `post` options, that allow to add
code before & after the `init` section

Finally, it contains the `final` option, being the concatenation of the
three previous options.

lib/neovim-plugin.nix

@@ -25,6 +25,11 @@
       # colorscheme
       isColorscheme ? false,
       colorscheme ? name,
+      # luaConfig
+      configLocation ? if isColorscheme then "extraConfigLuaPre" else "extraConfigLua",
+      # For some plugins it may not make sense to have a configuration attribute, as they are
+      # configured through some other mean, like global variables
+      hasConfigAttrs ? true,
       # options
       originalName ? name,
       # Can be a string, a list of strings, or a module option:
@@ -60,7 +65,14 @@
         let
           cfg = config.${namespace}.${name};
           opt = options.${namespace}.${name};
-          extraConfigNamespace = if isColorscheme then "extraConfigLuaPre" else "extraConfigLua";
+
+          setupCode = ''
+            require('${luaName}')${setup}(${
+              lib.optionalString (cfg ? settings) (helpers.toLuaObject cfg.settings)
+            })
+          '';
+
+          setLuaConfig = lib.setAttrByPath (lib.toList configLocation);
         in
         {
           meta = {
@@ -100,27 +112,40 @@
                 example = settingsExample;
               };
             }
+            // lib.optionalAttrs hasConfigAttrs {
+              luaConfig = lib.mkOption {
+                type = lib.nixvim.nixvimTypes.pluginLuaConfig;
+                default = { };
+                description = "The plugin's lua configuration";
+              };
+            }
             // extraOptions;
 
-          config = lib.mkIf cfg.enable (
-            lib.mkMerge [
-              {
-                extraPlugins = (lib.optional installPackage cfg.package) ++ extraPlugins;
-                inherit extraPackages;
-              }
-              (lib.optionalAttrs callSetup {
-                ${extraConfigNamespace} = ''
-                  require('${luaName}')${setup}(${
-                    lib.optionalString (cfg ? settings) (helpers.toLuaObject cfg.settings)
+          config =
+            assert lib.assertMsg (
+              callSetup -> configLocation != null
+            ) "When a plugin has no config attrs and has a setup function it must have a config location";
+            lib.mkIf cfg.enable (
+              lib.mkMerge (
+                [
+                  {
+                    extraPlugins = (lib.optional installPackage cfg.package) ++ extraPlugins;
+                    inherit extraPackages;
+                  }
+                  (lib.optionalAttrs (isColorscheme && (colorscheme != null)) {
+                    colorscheme = lib.mkDefault colorscheme;
                   })
-                '';
-              })
-              (lib.optionalAttrs (isColorscheme && (colorscheme != null)) {
-                colorscheme = lib.mkDefault colorscheme;
-              })
-              (extraConfig cfg)
-            ]
-          );
+                  (extraConfig cfg)
+                ]
+                ++ (lib.optionals (!hasConfigAttrs) [
+                  (lib.optionalAttrs callSetup (setLuaConfig setupCode))
+                ])
+                ++ (lib.optionals hasConfigAttrs [
+                  (lib.optionalAttrs callSetup { ${namespace}.${name}.luaConfig.content = setupCode; })
+                  (lib.optionalAttrs (configLocation != null) (setLuaConfig cfg.luaConfig.content))
+                ])
+              )
+            );
         };
     in
     {

lib/types.nix

@@ -113,4 +113,38 @@ rec {
         types.optionDescriptionPhrase (class: class == "noun" || class == "composite") elemType
       }";
     };
+
+  pluginLuaConfig = types.submodule (
+    { config, ... }:
+    {
+      options = {
+        pre = lib.mkOption {
+          type = types.lines;
+          default = "";
+          description = ''
+            Lua code inserted at the start of the plugin's configuration.
+            This is the same as using `lib.nixvim.utils.mkBeforeSection` when defining `content`.
+          '';
+        };
+        post = lib.mkOption {
+          type = types.lines;
+          default = "";
+          description = ''
+            Lua code inserted at the end of the plugin's configuration.
+            This is the same as using `lib.nixvim.utils.mkAfterSection` when defining `content`.
+          '';
+        };
+        content = lib.mkOption {
+          type = types.lines;
+          default = "";
+          description = "Configuration of the plugin";
+        };
+      };
+
+      config.content = lib.mkMerge [
+        (lib.nixvim.utils.mkBeforeSection config.pre)
+        (lib.nixvim.utils.mkAfterSection config.post)
+      ];
+    }
+  );
 }

lib/utils.nix

@@ -77,6 +77,12 @@ rec {
     in
     lib.concatStrings (map processWord words);
 
+  /**
+    Those helpers control the lua sections split in `pre, content, post`
+  */
+  mkBeforeSection = lib.mkOrder 300;
+  mkAfterSection = lib.mkOrder 2000;
+
   /**
     Capitalize a string by making the first character uppercase.