completion/blink-cmp: blink sources options

Use a submodule to allow arbitrary source additions.
Automatically load sources that are enabled.
Automatically add enabled sources via blink-cmp setupOpts.
Prepopulate with a few basic sources, disabled by default.

modules/plugins/completion/blink-cmp/config.nix

@@ -6,6 +6,8 @@
   inherit (lib.modules) mkIf;
   inherit (lib.strings) optionalString;
   inherit (lib.generators) mkLuaInline;
+  inherit (lib.attrsets) attrValues filterAttrs;
+  inherit (lib.lists) map;
   inherit (lib.nvim.lua) toLuaObject;
   inherit (builtins) concatStringsSep typeOf tryEval attrNames mapAttrs;
 
@@ -19,9 +21,12 @@
     else if (plugin ? pname && (tryEval plugin.pname).success)
     then plugin.pname
     else plugin.name;
+
+  enabledBlinkSources = filterAttrs (_source: definition: definition.enable) cfg.sourcePlugins;
+  blinkSourcePlugins = map (definition: definition.package) (attrValues enabledBlinkSources);
 in {
   vim = mkIf cfg.enable {
-    startPlugins = ["blink-compat"];
+    startPlugins = ["blink-compat"] ++ blinkSourcePlugins;
     lazy.plugins = {
       blink-cmp = {
         package = "blink-cmp";
@@ -32,12 +37,14 @@ in {
         #
         # event = ["InsertEnter" "CmdlineEnter"];
 
-        after = ''
-          ${optionalString config.vim.lazy.enable
-            (concatStringsSep "\n" (map
-              (package: "require('lz.n').trigger_load(${toLuaObject (getPluginName package)})")
-              cmpCfg.sourcePlugins))}
-        '';
+        after =
+          # lua
+          ''
+            ${optionalString config.vim.lazy.enable
+              (concatStringsSep "\n" (map
+                (package: "require('lz.n').trigger_load(${toLuaObject (getPluginName package)})")
+                cmpCfg.sourcePlugins))}
+          '';
       };
     };
 
@@ -45,13 +52,26 @@ in {
       enableSharedCmpSources = true;
       blink-cmp.setupOpts = {
         sources = {
-          default = ["lsp" "path" "snippets" "buffer"] ++ (attrNames cmpCfg.sources);
+          default =
+            [
+              "lsp"
+              "path"
+              "snippets"
+              "buffer"
+            ]
+            ++ (attrNames cmpCfg.sources)
+            ++ (attrNames enabledBlinkSources);
           providers =
             mapAttrs (name: _: {
               inherit name;
               module = "blink.compat.source";
             })
-            cmpCfg.sources;
+            cmpCfg.sources
+            // (mapAttrs (name: definition: {
+                inherit name;
+                inherit (definition) module;
+              })
+              enabledBlinkSources);
         };
         snippets = mkIf config.vim.snippets.luasnip.enable {
           preset = "luasnip";
@@ -67,16 +87,18 @@ in {
           ${mappings.next} = [
             "select_next"
             "snippet_forward"
-            (mkLuaInline ''
-              function(cmp)
-                local line, col = unpack(vim.api.nvim_win_get_cursor(0))
-                has_words_before = col ~= 0 and vim.api.nvim_buf_get_lines(0, line - 1, line, true)[1]:sub(col, col):match("%s") == nil
+            (mkLuaInline
+              # lua
+              ''
+                function(cmp)
+                  local line, col = unpack(vim.api.nvim_win_get_cursor(0))
+                  has_words_before = col ~= 0 and vim.api.nvim_buf_get_lines(0, line - 1, line, true)[1]:sub(col, col):match("%s") == nil
 
-                if has_words_before then
-                  return cmp.show()
+                  if has_words_before then
+                    return cmp.show()
+                  end
                 end
-              end
-            '')
+              '')
             "fallback"
           ];
           ${mappings.previous} = [