fix(colorscheme): try .lua files in 'rtp' before .vim files in 'pp' (#23727)

This ensures that colorschemes in 'rtp' are tried before ones in 'pp',
because some colorschemes in 'pp' may not work if not added to 'rtp'.

This also match the current documentation better.

2 files changed, 42 insertions, 2 deletions

diff --git a/src/nvim/highlight_group.c b/src/nvim/highlight_group.c
index 6965c53f59..a17fe2fc8c 100644
--- a/src/nvim/highlight_group.c
+++ b/src/nvim/highlight_group.c
@@ -697,10 +697,18 @@ int load_colors(char *name)
   char *buf = xmalloc(buflen);
   apply_autocmds(EVENT_COLORSCHEMEPRE, name, curbuf->b_fname, false, curbuf);
   snprintf(buf, buflen, "colors/%s.vim", name);
-  int retval = source_runtime(buf, DIP_START + DIP_OPT);
+  int retval = source_runtime(buf, 0);
   if (retval == FAIL) {
     snprintf(buf, buflen, "colors/%s.lua", name);
-    retval = source_runtime(buf, DIP_START + DIP_OPT);
+    retval = source_runtime(buf, 0);
+  }
+  if (retval == FAIL) {
+    snprintf(buf, buflen, "colors/%s.vim", name);
+    retval = source_runtime(buf, DIP_NORTP + DIP_START + DIP_OPT);
+  }
+  if (retval == FAIL) {
+    snprintf(buf, buflen, "colors/%s.lua", name);
+    retval = source_runtime(buf, DIP_NORTP + DIP_START + DIP_OPT);
   }
   xfree(buf);
   if (retval == OK) {
diff --git a/test/functional/lua/runtime_spec.lua b/test/functional/lua/runtime_spec.lua
index 72c99ac1f3..cd19ea4e49 100644
--- a/test/functional/lua/runtime_spec.lua
+++ b/test/functional/lua/runtime_spec.lua
@@ -61,6 +61,38 @@ describe('runtime:', function()
 
       eq('vim', eval('g:colorscheme'))
     end)
+
+    it("loads lua colorscheme in 'rtp' if vim version only exists in 'pp' #23724", function()
+      local pack_dir = 'Test_Pack'
+      mkdir_p(pack_dir)
+      finally(function()
+        rmdir(pack_dir)
+      end)
+      exec('set pp+=' .. pack_dir)
+
+      local pack_opt_dir = pack_dir .. sep .. 'pack' .. sep .. 'some_name' .. sep .. 'opt'
+      local colors_opt_dir = pack_opt_dir .. sep .. 'some_pack' .. sep .. 'colors'
+      mkdir_p(colors_opt_dir)
+
+      local rtp_colorscheme_file = colorscheme_folder .. sep .. 'new_colorscheme'
+      local pp_opt_colorscheme_file = colors_opt_dir .. sep .. 'new_colorscheme'
+
+      write_file(pp_opt_colorscheme_file .. '.lua', [[vim.g.colorscheme = 'lua_pp']])
+      exec('colorscheme new_colorscheme')
+      eq('lua_pp', eval('g:colorscheme'))
+
+      write_file(pp_opt_colorscheme_file .. '.vim', [[let g:colorscheme = 'vim_pp']])
+      exec('colorscheme new_colorscheme')
+      eq('vim_pp', eval('g:colorscheme'))
+
+      write_file(rtp_colorscheme_file .. '.lua', [[vim.g.colorscheme = 'lua_rtp']])
+      exec('colorscheme new_colorscheme')
+      eq('lua_rtp', eval('g:colorscheme'))
+
+      write_file(rtp_colorscheme_file .. '.vim', [[let g:colorscheme = 'vim_rtp']])
+      exec('colorscheme new_colorscheme')
+      eq('vim_rtp', eval('g:colorscheme'))
+    end)
   end)
 
   describe('compiler', function()