modules/performance/combine-plugins: propagate lua dependencies

Plugins from luarocks (e.g. telescope-nvim) have dependencies specified
in propagatedBuildInputs. These dependencies are not added as plugins in
Nvim runtime. They are added to LUA_PATH env var for wrapped neovim.
This commit collects all propagatedBuildInputs from input plugin list
and puts them in the combined plugin.
Note that such dependencies are never combined, because they are not
plugins.

modules/top-level/plugins/mk-plugin-pack.nix

@@ -28,24 +28,38 @@ let
       (builtins.concatMap (f: f ps))
     ];
 
-  # Combined plugin
-  combinedPlugin = pkgs.vimUtils.toVimPlugin (
-    pkgs.buildEnv {
-      name = "plugin-pack";
-      paths = overriddenPlugins;
-      inherit pathsToLink;
+  # propagatedBuildInputs contain lua dependencies
+  propagatedBuildInputs = lib.pipe pluginsToCombine [
+    (builtins.catAttrs "plugin")
+    (builtins.catAttrs "propagatedBuildInputs")
+    builtins.concatLists
+    lib.unique
+  ];
 
-      # Remove empty directories and activate vimGenDocHook
-      # TODO: figure out why we are running the `preFixup` hook in `postBuild`
-      postBuild = ''
-        find $out -type d -empty -delete
-        runHook preFixup
-      '';
-      passthru = {
-        inherit python3Dependencies;
-      };
-    }
-  );
+  # Combined plugin
+  combinedPlugin =
+    lib.pipe
+      {
+        name = "plugin-pack";
+        paths = overriddenPlugins;
+        inherit pathsToLink;
+
+        # buildEnv uses runCommand under the hood. runCommand doesn't run any build phases.
+        # To run custom commands buildEnv takes postBuild argument.
+        # fixupPhase is used for propagating build inputs and to trigger vimGenDocHook
+        postBuild = ''
+          find $out -type d -empty -delete
+          fixupPhase
+        '';
+        passthru = {
+          inherit python3Dependencies;
+        };
+      }
+      [
+        pkgs.buildEnv
+        pkgs.vimUtils.toVimPlugin
+        (drv: drv.overrideAttrs { inherit propagatedBuildInputs; })
+      ];
 
   # Combined plugin configs
   combinedConfig = lib.pipe pluginsToCombine [