bug#141: Process sentinel not called in batch mode

[Chong Yidong]

Helmut Eller <eller.helmut@gmail.com> wrote:

> process-sentinels aren't called in batch mode.  I'm not sure if this
> is a bug or the expected behavior, but I find this quite frustrating.
> To reproduce the problem do:
> $shell> cat test-sentinel.el

  (defvar sentinel-called nil)
  (defun main ()
    (let ((proc (start-process "test" nil "bash" "-c" "sleep 1 ; exit 20")))
      (set-process-sentinel proc (lambda (proc msg)
                                 (message "sentinel: %S %s" proc msg)
                                 (setq sentinel-called t)))
    (while (not sentinel-called)
      (message "status: %s exit-status: %s sentinel-called: %s" 
               (process-status proc) (process-exit-status proc) 
               sentinel-called)
      (sit-for 1)
      (accept-process-output proc 1))))
  (main)

> $shell> emacs -Q -batch -l test-sentinel.el

This problem occurs because wait_reading_process_output only calls
status_notify when given a nonzero DO_DISPLAY argument (process.c:4451).
Although wait_reading_process_output is called from many places in
Emacs, it is given a nonzero DO_DISPLAY argument only during
kbd_buffer_get_event.  But that function is never called in batch mode.

Maybe something like the attached patch should be applied.
Alternatively, we could change Faccept_process_output so that when Emacs
is in batch mode, it calls wait_reading_process_output with a nonzero
DO_DISPLAY argument.  Opinions?

*** trunk/src/process.c.~1.539.~        2008-04-09 13:46:04.000000000 -0400
--- trunk/src/process.c 2008-05-13 19:27:01.000000000 -0400
***************
*** 4414,4420 ****
         available, notify the user of the change right away.  After
         this explicit check, we'll let the SIGCHLD handler zap
         timeout to get our attention.  */
!       if (update_tick != process_tick && do_display)
        {
          SELECT_TYPE Atemp;
  #ifdef NON_BLOCKING_CONNECT
--- 4414,4421 ----
         available, notify the user of the change right away.  After
         this explicit check, we'll let the SIGCHLD handler zap
         timeout to get our attention.  */
!       if (update_tick != process_tick
!         && (do_display || noninteractive))
        {
          SELECT_TYPE Atemp;
  #ifdef NON_BLOCKING_CONNECT