neovim/runtime/indent.vim

" Vim support file to switch on loading indent files for file types
"
" Maintainer:	The Vim Project <https://github.com/vim/vim>
" Last Change:	2023 Aug 10
" Former Maintainer:	Bram Moolenaar <Bram@vim.org>

if exists("did_indent_on")
  finish
endif
let did_indent_on = 1

augroup filetypeindent
  au FileType * call s:LoadIndent()
  func! s:LoadIndent()
    if exists("b:undo_indent")
      exe b:undo_indent
      unlet! b:undo_indent b:did_indent
    endif
    let s = expand("<amatch>")
    if s != ""
      if exists("b:did_indent")
	unlet b:did_indent
      endif

      " When there is a dot it is used to separate filetype names.  Thus for
      " "aaa.bbb" load "indent/aaa.vim" and then "indent/bbb.vim".
      for name in split(s, '\.')
        " XXX: "[.]" in the pattern makes it a wildcard on Windows
        exe $'runtime! indent/{name}[.]{{vim,lua}}'
      endfor
    endif
  endfunc
augroup END