patch 8.1.0710: when using timers may wait for job exit quite long

Problem:    When using timers may wait for job exit quite long.
Solution:   Return from ui_wait_for_chars_or_timer() when a job or channel
            needs to be handled. (Ozaki Kiichi, closes #3783)

src/testdir/test_channel.vim

@@ -1893,3 +1893,40 @@ func Test_keep_pty_open()
   call assert_inrange(200, 1000, elapsed)
   call job_stop(job)
 endfunc
+
+func Test_job_start_in_timer()
+  if !has('job') || !has('timers')
+    return
+  endif
+
+  func OutCb(chan, msg)
+  endfunc
+
+  func ExitCb(job, status)
+    let g:val = 1
+    call Resume()
+  endfunc
+
+  func TimerCb(timer)
+    if has('win32')
+      let cmd = ['cmd', '/c', 'echo.']
+    else
+      let cmd = ['echo']
+    endif
+    let g:job = job_start(cmd, {'out_cb': 'OutCb', 'exit_cb': 'ExitCb'})
+    call substitute(repeat('a', 100000), '.', '', 'g')
+  endfunc
+
+  " We should be interrupted before 'updatetime' elapsed.
+  let g:val = 0
+  call timer_start(1, 'TimerCb')
+  let elapsed = Standby(&ut)
+  call assert_inrange(1, &ut / 2, elapsed)
+  call job_stop(g:job)
+
+  delfunc OutCb
+  delfunc ExitCb
+  delfunc TimerCb
+  unlet! g:val
+  unlet! g:job
+endfunc

src/ui.c

@@ -205,7 +205,7 @@ theend:
     return retval;
 }
 
-#if defined(FEAT_TIMERS) || defined(PROT)
+#if defined(FEAT_TIMERS) || defined(PROTO)
 /*
  * Wait for a timer to fire or "wait_func" to return non-zero.
  * Returns OK when something was read.
@@ -221,15 +221,18 @@ ui_wait_for_chars_or_timer(
     int	    due_time;
     long    remaining = wtime;
     int	    tb_change_cnt = typebuf.tb_change_cnt;
+# ifdef FEAT_JOB_CHANNEL
+    int	    brief_wait = TRUE;
+# endif
 
-    /* When waiting very briefly don't trigger timers. */
+    // When waiting very briefly don't trigger timers.
     if (wtime >= 0 && wtime < 10L)
 	return wait_func(wtime, NULL, ignore_input);
 
     while (wtime < 0 || remaining > 0)
     {
-	/* Trigger timers and then get the time in wtime until the next one is
-	 * due.  Wait up to that time. */
+	// Trigger timers and then get the time in wtime until the next one is
+	// due.  Wait up to that time.
 	due_time = check_due_timer();
 	if (typebuf.tb_change_cnt != tb_change_cnt)
 	{
@@ -238,11 +241,28 @@ ui_wait_for_chars_or_timer(
 	}
 	if (due_time <= 0 || (wtime > 0 && due_time > remaining))
 	    due_time = remaining;
+# ifdef FEAT_JOB_CHANNEL
+	if ((due_time < 0 || due_time > 10L)
+#  ifdef FEAT_GUI
+		&& !gui.in_use
+#  endif
+		&& (has_pending_job() || channel_any_readahead()))
+	{
+	    // There is a pending job or channel, should return soon in order
+	    // to handle them ASAP.  Do check for input briefly.
+	    due_time = 10L;
+	    brief_wait = TRUE;
+	}
+# endif
 	if (wait_func(due_time, interrupted, ignore_input))
 	    return OK;
-	if (interrupted != NULL && *interrupted)
-	    /* Nothing available, but need to return so that side effects get
-	     * handled, such as handling a message on a channel. */
+	if ((interrupted != NULL && *interrupted)
+# ifdef FEAT_JOB_CHANNEL
+		|| brief_wait
+# endif
+		)
+	    // Nothing available, but need to return so that side effects get
+	    // handled, such as handling a message on a channel.
 	    return FAIL;
 	if (wtime > 0)
 	    remaining -= due_time;
@@ -252,7 +272,7 @@ ui_wait_for_chars_or_timer(
 #endif
 
 /*
- * return non-zero if a character is available
+ * Return non-zero if a character is available.
  */
     int
 ui_char_avail(void)

src/version.c

@@ -799,6 +799,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    710,
 /**/
     709,
 /**/