vim-patch:8181c6e: runtime(luau): runtime support is incomplete

Problem:  runtime(luau): runtime support is incomplete.
Solution: Add Luau syntax, indent, filetype plugin and indent tests.

closes: vim/vim#20544

8181c6e313

Co-authored-by: Lopy <70210066+lopi-py@users.noreply.github.com>

runtime/ftplugin/luau.vim

@@ -1,14 +1,193 @@
 " Vim filetype plugin file
-" Language:	Luau
-" Maintainer:	None yet
-" Last Change:	2023 Apr 30
+" Language:     Luau
+" Maintainer:   Lopy (@lopi-py)
+" Last Change:  2026 Jun 16
 
 if exists("b:did_ftplugin")
   finish
 endif
+let b:did_ftplugin = 1
 
-" Luau is a superset of Lua
-runtime! ftplugin/lua.vim
+let s:cpo_save = &cpo
+set cpo&vim
 
+setlocal comments=:---,:--
+setlocal commentstring=--\ %s
+setlocal formatoptions-=t formatoptions+=croql
 
-" vim: nowrap sw=2 sts=2 ts=8
+let &l:define = '\<\%(function\|local\%(\s\+function\)\=\|const\%(\s\+function\)\=\|type\%(\s\+function\)\=\|export\s\+type\%(\s\+function\)\=\|class\|declare\s\+\%(function\|class\|extern\s\+type\)\)\>'
+let &l:include = '\<require\s*('
+setlocal includeexpr=s:LuauInclude(v:fname)
+setlocal suffixesadd=.luau,.lua
+
+let b:undo_ftplugin = "setl cms< com< def< fo< inc< inex< sua<"
+
+let s:attr = '@\%(\h\w*\|\[[^]]*\]\)\s*'
+let s:line_end = '\s*\%(--.*\)\=$'
+let s:end_pat = '^\s*end\>' .. s:line_end
+let s:end_block = '^\s*\%(' .. s:attr .. '\)*if\>.\{-}\<then\>' ..
+      \ '\|^\s*\%(' .. s:attr .. '\)*class\>\s\+\h' ..
+      \ '\|^\s*\%(' .. s:attr .. '\)*declare\s\+class\>\s\+\h' ..
+      \ '\|^\s*\%(' .. s:attr .. '\)*declare\s\+extern\s\+type\>.\{-}\<with\>' .. s:line_end
+
+if exists("loaded_matchit") && !exists("b:match_words")
+  let b:match_ignorecase = 0
+  let s:match_tail = ':\<return\>\|^\s*\%(else\|elseif\)\>:' .. s:end_pat ..
+        \ ',^\s*repeat\>:\<until\>,' ..
+        \ '\%(--\)\=\[\(=*\)\[:\]\1\]'
+  let s:match_words = '\<\%(do\|function\)\>\|' .. s:end_block .. s:match_tail
+  let s:match_words_no_function = '\<do\>\|' .. s:end_block .. s:match_tail
+  let b:match_words = "LuauMatchWords()"
+  let b:match_skip = 'LuauMatchSkip()'
+  let b:undo_ftplugin ..= " | unlet! b:match_words b:match_ignorecase b:match_skip"
+endif
+
+if (has("gui_win32") || has("gui_gtk")) && !exists("b:browsefilter")
+  let b:browsefilter = "Luau Source Files (*.luau)\t*.luau\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:, "luau_folding", 0)
+  setlocal foldmethod=expr
+  setlocal foldexpr=s:LuauFold()
+  let b:luau_lasttick = -1
+  let b:undo_ftplugin ..= " | setl foldexpr< foldmethod< | unlet! b:luau_lasttick b:luau_foldlists"
+endif
+
+" the rest of the file needs to be sourced only once per Vim session
+if exists("s:loaded_luau") || &cp
+  let &cpo = s:cpo_save
+  unlet s:cpo_save
+  finish
+endif
+let s:loaded_luau = 1
+
+function s:LuauInclude(fname) abort
+  let fname = a:fname
+  if fname =~# '^@'
+    return fname
+  endif
+  for path in [fname, fname .. ".luau", fname .. ".lua", fname .. "/init.luau", fname .. "/init.lua"]
+    if filereadable(path)
+      return path
+    endif
+  endfor
+  return fname
+endfunction
+
+function s:IsStringOrComment(lnum, col) abort
+  let name = synIDattr(synID(a:lnum, a:col, 1), "name")
+  return name =~# '^luau\%(Comment\|.*String\)'
+endfunction
+
+function s:LineCommentStart(lnum) abort
+  let line = getline(a:lnum)
+  let midx = stridx(line, '--')
+  while midx != -1
+    if !s:IsStringOrComment(a:lnum, midx + 1)
+      return midx
+    endif
+    let midx = stridx(line, '--', midx + 2)
+  endwhile
+  return -1
+endfunction
+
+function s:InDeclareClass(lnum) abort
+  let save_cursor = getcurpos()
+  call cursor(a:lnum - 1, 1)
+  let lnum = search('^\s*\%(end\>\|declare\s\+class\>\)', 'bcnW')
+  call setpos('.', save_cursor)
+  return lnum > 0 && getline(lnum) =~# '^\s*declare\s\+class\>'
+endfunction
+
+function LuauMatchSkip() abort
+  let lnum = line(".")
+  let col = col(".")
+  let comment = s:LineCommentStart(lnum)
+  return s:IsStringOrComment(lnum, col)
+        \ || (comment != -1 && col > comment)
+        \ || (expand("<cword>") ==# "function" && s:InDeclareClass(lnum))
+endfunction
+
+function LuauMatchWords() abort
+  if exists("s:match_words_no_function")
+        \ && expand("<cword>") ==# "function" && s:InDeclareClass(line("."))
+    return s:match_words_no_function
+  endif
+  return get(s:, "match_words", "")
+endfunction
+
+let s:fold_guard = '^\s*\%(@\|\%(do\|if\|repeat\|for\|while\|public' ..
+      \ '\|function\|return\|local\|const\|type\|export\|class' ..
+      \ '\|declare\|end\|until\)\>\)'
+
+let s:patterns = [
+      \ ['^\s*do\>' .. s:line_end, s:end_pat, 'block'],
+      \ ['^\s*if\>.\{-}\<then\>' .. s:line_end, s:end_pat, 'block'],
+      \ ['^\s*repeat\>' .. s:line_end, '^\s*until\>.*', 'block'],
+      \ ['^\s*for\>.\{-}\<do\>' .. s:line_end, s:end_pat, 'block'],
+      \ ['^\s*while\>.\{-}\<do\>' .. s:line_end, s:end_pat, 'block'],
+      \ ['^\s*\%(' .. s:attr .. '\)*\%(public\s\+\)\=function\>.*', s:end_pat, 'function'],
+      \ ['^\s*return\s\+function\>.*', s:end_pat, 'function'],
+      \ ['^\s*\%(' .. s:attr .. '\)*local\s\+function\>.*', s:end_pat, 'function'],
+      \ ['^\s*\%(' .. s:attr .. '\)*const\s\+function\>.*', s:end_pat, 'function'],
+      \ ['^\s*\%(' .. s:attr .. '\)*\%(export\s\+\)\=type\s\+function\>.*', s:end_pat, 'function'],
+      \ ['^\s*class\>\s\+\h.*', s:end_pat, 'class'],
+      \ ['^\s*declare\s\+class\>\s\+\h.*', s:end_pat, 'declare_class'],
+      \ ['^\s*declare\s\+extern\s\+type\>.\{-}\<with\>' .. s:line_end, s:end_pat, 'block'],
+      \ ]
+
+function s:LuauFold() abort
+  if b:luau_lasttick == b:changedtick
+    return b:luau_foldlists[v:lnum - 1]
+  endif
+  let b:luau_lasttick = b:changedtick
+
+  let b:luau_foldlists = []
+  let foldlist = []
+  let buf = getline(1, "$")
+  for line in buf
+    let open = 0
+    let end = 0
+    if line !~# s:fold_guard
+      call add(b:luau_foldlists, "" .. len(foldlist))
+      continue
+    endif
+    for t in s:patterns
+      let tagopen = t[0]
+      let tagend = t[1]
+      if line =~# tagopen
+        if t[2] ==# 'function' && len(foldlist) > 0 && foldlist[-1][2] ==# 'declare_class'
+          continue
+        endif
+        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
+    call add(b:luau_foldlists, prefix .. (len(foldlist) + end))
+  endfor
+
+  return b:luau_foldlists[v:lnum - 1]
+endfunction
+
+let &cpo = s:cpo_save
+unlet s:cpo_save
+
+" vim: nowrap sw=2 sts=2 ts=8 noet: