neovimUtils.packDir: init: extend vimUtils.packDir

in order for neovim to catch plugins dependencies, we fork
vimUtils.packDir as `neovimUtils.packDir` to merge the various plugins
nix-support/propagated-build-inputs files in the packDir derivation
$out/nix-support/propagated-build-inputs where there was previously
none.

Having a fork allows us to experiment without impacting vim plugins.

Once we are more confident this doesn't break stuff and/or the
implementation is final, we can merge the fork back or replace one by
the other.

pkgs/applications/editors/neovim/utils.nix

@@ -229,12 +229,36 @@ let
         ln -s ${grammar}/parser $out/parser/${name}.so
       '');
 
+  /*
+    Fork of vimUtils.packDir that additionnally generates a propagated-build-inputs-file that
+    can be used by the lua hooks to generate a proper LUA_PATH
+
+    Generates a packpath folder as expected by vim
+       Example:
+       packDir ( {myVimPackage = { start = [ vimPlugins.vim-fugitive ]; opt = []; }; })
+       => "/nix/store/xxxxx-pack-dir"
+  */
+  packDir = packages:
+  let
+    rawPackDir = vimUtils.packDir packages;
+
+  in
+    rawPackDir.override ({
+    postBuild = ''
+      mkdir $out/nix-support
+      for i in $(find -L $out -name propagated-build-inputs ); do
+        cat "$i" >> $out/nix-support/propagated-build-inputs
+      done
+      '';});
+
+
 in
 {
   inherit makeNeovimConfig;
   inherit generateProviderRc;
   inherit legacyWrapper;
   inherit grammarToPlugin;
+  inherit packDir;
 
   inherit buildNeovimPlugin;
   buildNeovimPluginFrom2Nix = lib.warn "buildNeovimPluginFrom2Nix was renamed to buildNeovimPlugin" buildNeovimPlugin;

pkgs/applications/editors/neovim/wrapper.nix

@@ -24,6 +24,8 @@ let
     , withNodeJs ? false
     , withPerl ? false
     , rubyEnv ? null
+
+    # wether to create symlinks in $out/bin/vi(m) -> $out/bin/nvim
     , vimAlias ? false
     , viAlias ? false
 
@@ -45,6 +47,8 @@ let
   stdenv.mkDerivation (finalAttrs:
   let
 
+    finalPackdir = neovimUtils.packDir packpathDirs;
+
     rcContent = ''
       ${luaRcContent}
     '' + lib.optionalString (!isNull neovimRcContent) ''
@@ -58,9 +62,10 @@ let
           [
             "--add-flags" ''--cmd "lua ${providerLuaRc}"''
             # (lib.intersperse "|" hostProviderViml)
-          ] ++ lib.optionals (packpathDirs.myNeovimPackages.start != [] || packpathDirs.myNeovimPackages.opt != []) [
-            "--add-flags" ''--cmd "set packpath^=${vimUtils.packDir packpathDirs}"''
-            "--add-flags" ''--cmd "set rtp^=${vimUtils.packDir packpathDirs}"''
+          ]
+          ++ lib.optionals (packpathDirs.myNeovimPackages.start != [] || packpathDirs.myNeovimPackages.opt != []) [
+            "--add-flags" ''--cmd "set packpath^=${finalPackdir}"''
+            "--add-flags" ''--cmd "set rtp^=${finalPackdir}"''
           ]
           ;