vim-patch:00a00f5: runtime(lua): Update lua ftplugin and documentation

Problem:
- The doc says the default `g:lua_subversion` is 2, but in fact it is 3
  (see `runtime/syntax/lua.vim`)
- `includeexpr` doesn't work with module in `init.lua`

Solution:
- Update documentation
- Assign value to option `&include`
- Add function `LuaInclude` and assign it to `l:&includeexpr`

closes: vim/vim#16655

https://github.com/vim/vim/commit/00a00f5d3fc8dcf08e959c207a90f5902abc6a08

Co-authored-by: brianhuster <phambinhanctb2004@gmail.com>
Co-authored-by: dkearns <dougkearns@gmail.com>

4 files changed, 50 insertions, 15 deletions

diff --git a/runtime/doc/filetype.txt b/runtime/doc/filetype.txt
index b3fe13bfbd..f1d287b1bb 100644
--- a/runtime/doc/filetype.txt
+++ b/runtime/doc/filetype.txt
@@ -695,7 +695,18 @@ To enable the recognition of Markdown comments each time after removing
 re-source "javaformat.vim" for Vim versions greater than `8.2.1397`: >
 	runtime autoload/javaformat.vim
 <
+LUA							*ft-lua-plugin*
 
+					*g:lua_version* *g:lua_subversion*
+Lua filetype's 'includeexpr' and |ft-lua-syntax| highlighting use the global
+variables "g:lua_version" and "g:lua_subversion" to determine the version of
+Lua to use (5.3 is the default)
+
+For example, to use Lua 5.1, set the variables like this: >
+
+	let g:lua_version = 5
+	let g:lua_subversion = 1
+<
 MAIL							*ft-mail-plugin*
 
 Options:
diff --git a/runtime/doc/syntax.txt b/runtime/doc/syntax.txt
index 75d6d85183..3a19ee55c3 100644
--- a/runtime/doc/syntax.txt
+++ b/runtime/doc/syntax.txt
@@ -1870,13 +1870,9 @@ instead, and the name of your source file should be `*.pike`
 
 LUA						*lua.vim* *ft-lua-syntax*
 
-The Lua syntax file can be used for versions 4.0, 5.0, 5.1 and 5.2 (5.2 is
-the default). You can select one of these versions using the global variables
-lua_version and lua_subversion. For example, to activate Lua
-5.1 syntax highlighting, set the variables like this: >
-
-	:let lua_version = 5
-	:let lua_subversion = 1
+The Lua syntax file can be used for versions 4.0, 5.0+. You can select one of
+these versions using the global variables |g:lua_version| and
+|g:lua_subversion|.
 
 
 MAIL						*mail.vim* *ft-mail.vim*
diff --git a/runtime/ftplugin/lua.vim b/runtime/ftplugin/lua.vim
index 80cbba78a2..914e7ab6db 100644
--- a/runtime/ftplugin/lua.vim
+++ b/runtime/ftplugin/lua.vim
@@ -4,14 +4,24 @@
 " Previous Maintainer:	Max Ischenko <mfi@ukr.net>
 " Contributor:		Dorai Sitaram <ds26@gte.com>
 "			C.D. MacEachern <craig.daniel.maceachern@gmail.com>
-"			Tyler Miller <tmillr@proton.me>
-" Last Change:		2024 Jan 14
+"			Phạm Bình An <phambinhanctb2004@gmail.com>
+" Last Change:		2025 Feb 25
 
 if exists("b:did_ftplugin")
   finish
 endif
 let b:did_ftplugin = 1
 
+" keep in sync with syntax/lua.vim
+if !exists("lua_version")
+  " Default is lua 5.3
+  let lua_version = 5
+  let lua_subversion = 3
+elseif !exists("lua_subversion")
+  " lua_version exists, but lua_subversion doesn't. In this case set it to 0
+  let lua_subversion = 0
+endif
+
 let s:cpo_save = &cpo
 set cpo&vim
 
@@ -21,11 +31,11 @@ setlocal formatoptions-=t formatoptions+=croql
 
 let &l:define = '\<function\|\<local\%(\s\+function\)\='
 
-" TODO: handle init.lua
-setlocal includeexpr=tr(v:fname,'.','/')
+let &l:include = '\v<((do|load)file|require)[^''"]*[''"]\zs[^''"]+'
+setlocal includeexpr=LuaInclude(v:fname)
 setlocal suffixesadd=.lua
 
-let b:undo_ftplugin = "setlocal cms< com< def< fo< inex< sua<"
+let b:undo_ftplugin = "setlocal cms< com< def< fo< inc< inex< sua<"
 
 if exists("loaded_matchit") && !exists("b:match_words")
   let b:match_ignorecase = 0
@@ -48,7 +58,24 @@ if (has("gui_win32") || has("gui_gtk")) && !exists("b:browsefilter")
   let b:undo_ftplugin ..= " | unlet! b:browsefilter"
 endif
 
-let &cpo = s:cpo_save
-unlet s:cpo_save
+" The rest of the file needs to be :sourced only once per Vim session
+if exists("s:loaded_lua") || &cp
+  let &cpo = s:cpo_save
+  unlet s:cpo_save
+  finish
+endif
+let s:loaded_lua = 1
+
+function LuaInclude(fname) abort
+  let lua_ver = str2float(printf("%d.%02d", g:lua_version, g:lua_subversion))
+  let fname = tr(a:fname, '.', '/')
+  let paths = lua_ver >= 5.03 ?  [ fname.'.lua', fname.'/init.lua' ] : [ fname.'.lua' ]
+  for path in paths
+    if filereadable(path)
+      return path
+    endif
+  endfor
+  return fname
+endfunction
 
 " vim: nowrap sw=2 sts=2 ts=8 noet:
diff --git a/runtime/syntax/lua.vim b/runtime/syntax/lua.vim
index 9c5a490582..f5851d024f 100644
--- a/runtime/syntax/lua.vim
+++ b/runtime/syntax/lua.vim
@@ -2,7 +2,7 @@
 " Language:     Lua 4.0, Lua 5.0, Lua 5.1, Lua 5.2 and Lua 5.3
 " Maintainer:   Marcus Aurelius Farias <masserahguard-lua 'at' yahoo com>
 " First Author: Carlos Augusto Teixeira Mendes <cmendes 'at' inf puc-rio br>
-" Last Change:  2022 Sep 07
+" Last Change:  2025 Feb 25
 " Options:      lua_version = 4 or 5
 "               lua_subversion = 0 (for 4.0 or 5.0)
 "                               or 1, 2, 3 (for 5.1, 5.2 or 5.3)
@@ -16,6 +16,7 @@ endif
 let s:cpo_save = &cpo
 set cpo&vim
 
+" keep in sync with ftplugin/lua.vim
 if !exists("lua_version")
   " Default is lua 5.3
   let lua_version = 5