vimUtils: add dependency logic to nativeImpl

nativeImpl previously simply ignored dependency information.

doc/languages-frameworks/vim.section.md

@@ -48,7 +48,7 @@ neovim.override {
 
 ## Managing plugins with Vim packages
 
-To store you plugins in Vim packages the following example can be used:
+To store you plugins in Vim packages (the native vim plugin manager, see `:help packages`) the following example can be used:
 
 ```
 vim_configurable.customize {
@@ -56,6 +56,8 @@ vim_configurable.customize {
     # loaded on launch
     start = [ youcompleteme fugitive ];
     # manually loadable by calling `:packadd $plugin-name`
+    # however, if a vim plugin has a dependency that is not explicitly listed in
+	# opt that dependency will always be added to start to avoid confusion.
     opt = [ phpCompletion elm-vim ];
     # To automatically load a plugin when opening a filetype, add vimrc lines like:
     # autocmd FileType php :packadd phpCompletion
@@ -63,6 +65,7 @@ vim_configurable.customize {
 }
 ```
 
+`myVimPackage` is an arbitrary name for the generated package. You can choose any name you like.
 For Neovim the syntax is:
 
 ```
@@ -74,6 +77,8 @@ neovim.override {
     packages.myVimPackage = with pkgs.vimPlugins; {
       # see examples below how to use custom packages
       start = [ ];
+      # If a vim plugin has a dependency that is not explicitly listed in
+      # opt that dependency will always be added to start to avoid confusion.
       opt = [ ];
     };
   };

pkgs/misc/vim-plugins/vim-utils.nix

@@ -293,8 +293,18 @@ let
       (let
         link = (packageName: dir: pluginPath: "ln -sf ${pluginPath}/share/vim-plugins/* $out/pack/${packageName}/${dir}");
         packageLinks = (packageName: {start ? [], opt ? []}:
+        let
+          # `nativeImpl` expects packages to be derivations, not strings (as
+          # opposed to older implementations that have to maintain backwards
+          # compatibility). Therefore we don't need to deal with "knownPlugins"
+          # and can simply pass `null`.
+          depsOfOptionalPlugins = lib.subtractLists opt (findDependenciesRecursively null opt);
+          startWithDeps = findDependenciesRecursively null start;
+        in
           ["mkdir -p $out/pack/${packageName}/start"]
-          ++ (builtins.map (link packageName "start") start)
+          # To avoid confusion, even dependencies of optional plugins are added
+          # to `start` (except if they are explicitly listed as optional plugins).
+          ++ (builtins.map (link packageName "start") (lib.unique (startWithDeps ++ depsOfOptionalPlugins)))
           ++ ["mkdir -p $out/pack/${packageName}/opt"]
           ++ (builtins.map (link packageName "opt") opt)
         );