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.

" Test for joining lines.

func Test_join_with_count()
  new
  call setline(1, ['one', 'two', 'three', 'four'])
  normal J
  call assert_equal('one two', getline(1))
  %del
  call setline(1, ['one', 'two', 'three', 'four'])
  normal 10J
  call assert_equal('one two three four', getline(1))
  quit!
endfunc