neovim/runtime/indent/treetop.vim

" Vim indent file
" Language:		Treetop
" Maintainer:		Doug Kearns <dougkearns@gmail.com>
" Previous Maintainer:	Nikolai Weibull <now@bitwi.se>
" Last Change:		2022 April 25

if exists("b:did_indent")
  finish
endif
let b:did_indent = 1

setlocal indentexpr=GetTreetopIndent()
setlocal indentkeys=0{,0},!^F,o,O,=end
setlocal nosmartindent

let b:undo_indent = "setl inde< indk< si<"

if exists("*GetTreetopIndent")
  finish
endif

function GetTreetopIndent()
  let pnum = prevnonblank(v:lnum - 1)
  if pnum == 0
    return 0
  endif

  let ind = indent(pnum)
  let line = getline(pnum)

  if line =~ '^\s*\%(grammar\|module\|rule\)\>'
    let ind += shiftwidth()
  endif

  let line = getline(v:lnum)
  if line =~ '^\s*end\>'
    let ind -= shiftwidth()
  end

  return ind
endfunction