patch 9.1.1969: Wrong cursor position after formatting with long 'formatprg'

Problem:  Wrong cursor position after formatting with long 'formatprg'.
Solution: Don't show hit-enter prompt when there are stuffed characters.

Previously a stuffed character at the hit-enter prompt will dismiss the
prompt immediately and be put in the typeahead buffer, which leads to
incorrect behavior as the typeahead buffer is processed after the stuff
buffers. Using vungetc() when KeyStuffed is TRUE can fix this problem,
but since the hit-enter prompt isn't visible anyway (and is likely not
desired here), just skip the prompt instead, which also avoids a wait
when using "wait" instead of "hit-enter" in 'messagesopt'.

fixes:  #18905
closes: #18906

Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

src/getchar.c

@@ -439,7 +439,7 @@ stuff_empty(void)
 #if defined(FEAT_EVAL)
 /*
  * Return TRUE if readbuf1 is empty.  There may still be redo characters in
- * redbuf2.
+ * readbuf2.
  */
     int
 readbuf1_empty(void)

src/message.c

@@ -1287,6 +1287,11 @@ wait_return(int redraw)
 	c = CAR;		// no need for a return in ex mode
 	got_int = FALSE;
     }
+    else if (!stuff_empty())
+	// When there are stuffed characters, the next stuffed character will
+	// dismiss the hit-enter prompt immediately and have to be put back, so
+	// instead just don't show the hit-enter prompt at all.
+	c = CAR;
     else
     {
 	// Make sure the hit-return prompt is on screen when 'guioptions' was

src/testdir/dumps/Test_long_formatprg_no_hit_enter_1.dump

@@ -0,0 +1,10 @@
+>1+0&#ffffff0|0| @72
+|1@1| @72
+|1|2| @72
+|1|3| @72
+|1|4| @72
+|1|5| @72
+|1|6| @72
+|1|7| @72
+|1|8| @72
+@57|1|0|,|1| @9|2|9|%| 

src/testdir/dumps/Test_long_formatprg_no_hit_enter_2.dump

@@ -0,0 +1,10 @@
+|1+0&#ffffff0|0| @72
+|1|0| @72
+|1@1| @72
+|1@1| @72
+|1|2| @72
+>1|2| @72
+|1|3| @72
+|1|4| @72
+|1|5| @72
+@57|1|5|,|1| @9|2|6|%| 

src/testdir/dumps/Test_long_formatprg_no_hit_enter_3.dump

@@ -0,0 +1,10 @@
+|1+0&#ffffff0|0| @72
+|1|0| @72
+|1@1| @72
+|1@1| @72
+|1|2| @72
+>1|2| @72
+|1|3| @72
+|1|4| @72
+|1|5| @72
+|3| |l|i|n|e|s| |f|i|l|t|e|r|e|d| @40|1|5|,|1| @9|2|6|%| 

src/testdir/test_messages.vim

@@ -786,4 +786,29 @@ func Test_messagesopt_wait()
   call StopVimInTerminal(buf)
 endfunc
 
+" Check that using a long 'formatprg' doesn't cause a hit-enter prompt or
+" wrong cursor position.
+func Test_long_formatprg_no_hit_enter()
+  CheckScreendump
+  CheckExecutable sed
+
+  let lines =<< trim END
+    setlocal scrolloff=0
+    call setline(1, range(1, 40))
+    let &l:formatprg = $'sed{repeat(' ', &columns)}p'
+    normal 20Gmz
+    normal 10Gzt
+  END
+  call writefile(lines, 'XtestLongFormatprg', 'D')
+  let buf = RunVimInTerminal('-S XtestLongFormatprg', #{rows: 10})
+  call VerifyScreenDump(buf, 'Test_long_formatprg_no_hit_enter_1', {})
+  call term_sendkeys(buf, 'gq2j')
+  call VerifyScreenDump(buf, 'Test_long_formatprg_no_hit_enter_2', {})
+  call term_sendkeys(buf, ":messages\<CR>")
+  call VerifyScreenDump(buf, 'Test_long_formatprg_no_hit_enter_3', {})
+
+  " clean up
+  call StopVimInTerminal(buf)
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab

src/version.c

@@ -729,6 +729,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1969,
 /**/
     1968,
 /**/