runtime/ftplugin/lua.vim

" Vim filetype plugin file.
" Language:             Lua
" Maintainer:           Doug Kearns <dougkearns@gmail.com>
" 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>
"                       Phạm Bình An <phambinhanctb2004@gmail.com>
"                       @konfekt
" Last Change:          2025 Apr 04

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

setlocal comments=:---,:--
setlocal commentstring=--\ %s
setlocal formatoptions-=t formatoptions+=croql

let &l:define = '\<function\|\<local\%(\s\+function\)\='

let &l:include = '\<\%(\%(do\|load\)file\|require\)\s*('
setlocal includeexpr=s:LuaInclude(v:fname)
setlocal suffixesadd=.lua

let b:undo_ftplugin = "setl cms< com< def< fo< inc< inex< sua<"

if exists("loaded_matchit") && !exists("b:match_words")
  let b:match_ignorecase = 0
  let b:match_words =
        \ '\<\%(do\|function\|if\)\>:' ..
        \ '\<\%(return\|else\|elseif\)\>:' ..
        \ '\<end\>,' ..
        \ '\<repeat\>:\<until\>,' ..
        \ '\%(--\)\=\[\(=*\)\[:]\1]'
  let b:undo_ftplugin ..= " | unlet! b:match_words b:match_ignorecase"
endif

if (has("gui_win32") || has("gui_gtk")) && !exists("b:browsefilter")
  let b:browsefilter = "Lua Source Files (*.lua)\t*.lua\n"
  if has("win32")
    let b:browsefilter ..= "All Files (*.*)\t*\n"
  else
    let b:browsefilter ..= "All Files (*)\t*\n"
  endif
  let b:undo_ftplugin ..= " | unlet! b:browsefilter"
endif

if has("folding") && get(g:, "lua_folding", 0)
  setlocal foldmethod=expr
  setlocal foldexpr=s:LuaFold()
  let b:lua_lasttick = -1
  let b:undo_ftplugin ..= " | setl foldexpr< foldmethod< | unlet! b:lua_lasttick b:lua_foldlists"
endif

" 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 s: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

let s:patterns = [
    \ ['do', 'end'],
    \ ['if\s+.+\s+then', 'end'],
    \ ['repeat', 'until\s+.+'],
    \ ['for\s+.+\s+do', 'end'],
    \ ['while\s+.+\s+do', 'end'],
    \ ['function.+', 'end'],
    \ ['return\s+function.+', 'end'],
    \ ['local\s+function\s+.+', 'end'],
    \ ]

function s:LuaFold() abort
  if b:lua_lasttick == b:changedtick
    return b:lua_foldlists[v:lnum - 1]
  endif
  let b:lua_lasttick = b:changedtick

  let b:lua_foldlists = []
  let foldlist = []
  let buf = getline(1, "$")
  for line in buf
    for t in s:patterns
      let open = 0
      let end = 0
      let tagopen  = '\v^\s*' .. t[0] ..'\s*$'
      let tagend = '\v^\s*' .. t[1] ..'\s*$'
      if line =~# tagopen
        call add(foldlist, t)
        let open = 1
        break
      elseif line =~# tagend
        if len(foldlist) > 0 && line =~# foldlist[-1][1]
          call remove(foldlist, -1)
          let end = 1
        else
          let foldlist = []
        endif
        break
      endif
    endfor
    let prefix = ""
    if open == 1 | let prefix = ">" | endif
    if end == 1 | let prefix = "<" | endif
    let b:lua_foldlists += [prefix..(len(foldlist) + end)]
  endfor

  return b:lua_foldlists[v:lnum - 1]
endfunction

if !has('vim9script')
  let &cpo = s:cpo_save
  unlet s:cpo_save

  finish
endif

delfunction! s:LuaFold
def s:LuaFold(): string
  if b:lua_lasttick == b:changedtick
    return b:lua_foldlists[v:lnum - 1]
  endif
  b:lua_lasttick = b:changedtick

  b:lua_foldlists = []
  var foldlist = []
  var buf = getline(1, "$")
  for line in buf
    var open = 0
    var end = 0
    for t in patterns
      var tagopen  = '\v^\s*' .. t[0] .. '\s*$'
      var tagend = '\v^\s*' .. t[1] .. '\s*$'
      if line =~# tagopen
        add(foldlist, t)
        open = 1
        break
      elseif line =~# tagend
        if len(foldlist) > 0 && line =~# foldlist[-1][1]
          end = 1
          remove(foldlist, -1)
        else
          foldlist = []
        endif
        break
      endif
    endfor
    var prefix = ""
    if open == 1 | prefix = ">" | endif
    if end == 1 | prefix = "<" | endif
    b:lua_foldlists += [prefix .. (len(foldlist) + end)]
  endfor
  return b:lua_foldlists[v:lnum - 1]
enddef

let &cpo = s:cpo_save
unlet s:cpo_save
" vim: nowrap sw=2 sts=2 ts=8 noet: