commit https://github.com/vim/vim/commit/437905c25d4cedfa16d0f87392e4a000d22362b7 Author: Bram Moolenaar <Bram@vim.org> Date: Tue Apr 26 19:01:05 2016 +0200 patch 7.4.1789 Problem: Cannot use ch_read() in the close callback. Solution: Do not discard the channel if there is readahead. Do not discard readahead if there is a close callback.

" Tests for :undo

func Test_ex_undo()
  new ex-undo
  setlocal ul=10
  exe "normal ione\n\<Esc>"
  setlocal ul=10
  exe "normal itwo\n\<Esc>"
  setlocal ul=10
  exe "normal ithree\n\<Esc>"
  call assert_equal(4, line('$'))
  undo
  call assert_equal(3, line('$'))
  undo 1
  call assert_equal(2, line('$'))
  undo 0
  call assert_equal(1, line('$'))
  quit!
endfunc