neovim: add extraLuaPackages to wrapNeovimUnstable (#499571)

doc/languages-frameworks/neovim.section.md

@@ -64,6 +64,7 @@ For instance, `sqlite-lua` needs `g:sqlite_clib_path` to be set to work. Nixpkgs
 - `wrapRc`: Nix, not being able to write in your `$HOME`, loads the
   generated Neovim configuration via the `$VIMINIT` environment variable, i.e. : `export VIMINIT='lua dofile("/nix/store/…-init.lua")'`. This has side effects like preventing Neovim from sourcing your `init.lua` in `$XDG_CONFIG_HOME/nvim` (see bullet 7 of [`:help startup`](https://neovim.io/doc/user/starting.html#startup) in Neovim). Disable it if you want to generate your own wrapper. You can still reuse the generated vimscript init code via `neovim.passthru.initRc`.
 - `plugins`: A list of plugins to add to the wrapper.
+- `extraLuaPackages`: A function passed on to `lua.withPackages`
 - `withPython3`, `withNodeJs`, `withRuby` control when to enable neovim
   providers (see `:h provider`).
 
@@ -90,6 +91,7 @@ wrapNeovimUnstable neovim-unwrapped {
     (nvim-treesitter.withPlugins (p: [ p.nix p.python ]))
     hex-nvim
   ];
+  extraLuaPackages = lp: [ lp.mpack ];
   withPython3 = true;
   withNodeJs = false;
   withRuby = false;

pkgs/applications/editors/neovim/tests/default.nix

@@ -348,12 +348,12 @@ pkgs.lib.recurseIntoAttrs rec {
     configure.packages.foo.start = with vimPlugins; [ deoplete-nvim ];
   };
 
-  nvimWithLuaPackages = wrapNeovim2 "-with-lua-packages" (makeNeovimConfig {
+  nvimWithLuaPackages = wrapNeovim2 "-with-lua-packages" {
     extraLuaPackages = ps: [ ps.mpack ];
-    customRC = ''
-      lua require("mpack")
+    luaRcContent = ''
+      require("mpack")
     '';
-  });
+  };
 
   nvim_with_lua_packages = runTest nvimWithLuaPackages ''
     ${nvimWithLuaPackages}/bin/nvim -V3log.txt -i NONE --noplugin +quitall! -e

pkgs/applications/editors/neovim/wrapper.nix

@@ -69,6 +69,8 @@ let
       # { plugin=far-vim; config = "let g:far#source='rg'"; optional = false; }
       # ]
       plugins ? [ ],
+      # the function you would have passed to lua.withPackages
+      extraLuaPackages ? (_: [ ]),
       ...
     }@attrs:
     assert
@@ -105,8 +107,23 @@ let
         packpathDirs.myNeovimPackages = vimPackageInfo.vimPackage;
         finalPackdir = neovimUtils.packDir packpathDirs;
 
+        luaPathLuaRc =
+          let
+            luaEnv = lua.withPackages extraLuaPackages;
+
+            # getLuaPath / getLuaCPath are not interpreter dependant at the moment and might thus cause
+            # errors between luajit/Puc lua
+            generatedLuaPath = lua.pkgs.getLuaPath luaEnv;
+            generatedLuaCPath = lua.pkgs.getLuaCPath luaEnv;
+          in
+          ''
+            package.path = "${generatedLuaPath}".. ";" .. package.path
+            package.cpath = "${generatedLuaCPath}".. ";" .. package.cpath
+          '';
+
         rcContent = lib.concatStringsSep "\n" (
           [
+            luaPathLuaRc
             providerLuaRc
           ]
           ++ lib.optional (luaRcContent != "") luaRcContent