patch 9.1.1539: completion: messages don't respect 'shm' setting

Problem:  completion: messages don't respect 'shm' setting
Solution: Turn off completion messages when 'shortmess' includes "c"
          (Girish Palya).

`:set shortmess+=c` is intended to reduce noise during completion by
suppressing messages.
Previously, some completion messages still appeared regardless of this setting.

This change ensures that **all** completion-related messages are suppressed
when `'c'` is present in `'shortmess'`.

Not entirely sure if the original behavior was intentional. If there's a
reason certain messages were always shown, feel free to close this without
merging.

closes: #17737

Signed-off-by: Girish Palya <girishji@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

src/insexpand.c

@@ -6600,6 +6600,7 @@ ins_compl_start(void)
 
     if (compl_status_adding())
     {
+	if (!shortmess(SHM_COMPLETIONMENU))
 	    edit_submode_pre = (char_u *)_(" Adding");
 	if (ctrl_x_mode_line_or_eval())
 	{
@@ -6627,10 +6628,13 @@ ins_compl_start(void)
 	compl_startpos.col = compl_col;
     }
 
+    if (!shortmess(SHM_COMPLETIONMENU))
+    {
 	if (compl_cont_status & CONT_LOCAL)
 	    edit_submode = (char_u *)_(ctrl_x_msgs[CTRL_X_LOCAL_MSG]);
 	else
 	    edit_submode = (char_u *)_(CTRL_X_MSG(ctrl_x_mode));
+    }
 
     // If any of the original typed text has been changed we need to fix
     // the redo buffer.
@@ -6655,11 +6659,14 @@ ins_compl_start(void)
     // showmode might reset the internal line pointers, so it must
     // be called before line = ml_get(), or when this address is no
     // longer needed.  -- Acevedo.
+    if (!shortmess(SHM_COMPLETIONMENU))
+    {
 	edit_submode_extra = (char_u *)_("-- Searching...");
 	edit_submode_highl = HLF_COUNT;
 	showmode();
 	edit_submode_extra = NULL;
 	out_flush();
+    }
 
     return OK;
 }
@@ -6821,6 +6828,7 @@ ins_complete(int c, int enable_pum)
     else
 	compl_cont_status &= ~CONT_S_IPOS;
 
+    if (!shortmess(SHM_COMPLETIONMENU))
 	ins_compl_show_statusmsg();
 
     // Show the popup menu, unless we got interrupted.

src/testdir/dumps/Test_shortmess_complmsg_1.dump

@@ -0,0 +1,12 @@
+|h+0&#ffffff0|e|l@1|o| @69
+|h|u|l@1|o| @69
+|h|e@2| @70
+|h|e|l@1|o> @69
+|h+0#0000001#e0e0e08|e|l@1|o| @9| +0#4040ff13#ffffff0@59
+|h+0#0000001#ffd7ff255|u|l@1|o| @9| +0#4040ff13#ffffff0@59
+|h+0#0000001#ffd7ff255|e@2| @10| +0#4040ff13#ffffff0@59
+|~| @73
+|~| @73
+|~| @73
+|~| @73
+|-+2#0000000&@1| |K|e|y|w|o|r|d| |c|o|m|p|l|e|t|i|o|n| |(|^|N|^|P|)| |m+0#00e0003&|a|t|c|h| |1| |o|f| |3| +0#0000000&@33

src/testdir/dumps/Test_shortmess_complmsg_2.dump

@@ -0,0 +1,12 @@
+|h+0&#ffffff0|e|l@1|o| @69
+|h|u|l@1|o| @69
+|h|e@2| @70
+|h|e|l@1|o> @69
+|h+0#0000001#e0e0e08|e|l@1|o| @9| +0#4040ff13#ffffff0@59
+|h+0#0000001#ffd7ff255|u|l@1|o| @9| +0#4040ff13#ffffff0@59
+|h+0#0000001#ffd7ff255|e@2| @10| +0#4040ff13#ffffff0@59
+|~| @73
+|~| @73
+|~| @73
+|~| @73
+|-+2#0000000&@1| |I|N|S|E|R|T| |-@1| +0&&@62

src/testdir/test_ins_complete.vim

@@ -4976,4 +4976,25 @@ func Test_nonkeyword_trigger()
   unlet g:CallCount
 endfunc
 
+" Test that option shortmess=c turns off completion messages
+func Test_shortmess()
+  CheckScreendump
+
+  let lines =<< trim END
+    call setline(1, ['hello', 'hullo', 'heee'])
+  END
+
+  call writefile(lines, 'Xpumscript', 'D')
+  let buf = RunVimInTerminal('-S Xpumscript', #{rows: 12})
+  call term_sendkeys(buf, "Goh\<C-N>")
+  call TermWait(buf, 200)
+  call VerifyScreenDump(buf, 'Test_shortmess_complmsg_1', {})
+  call term_sendkeys(buf, "\<ESC>:set shm+=c\<CR>")
+  call term_sendkeys(buf, "Sh\<C-N>")
+  call TermWait(buf, 200)
+  call VerifyScreenDump(buf, 'Test_shortmess_complmsg_2', {})
+
+  call StopVimInTerminal(buf)
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab nofoldenable

src/version.c

@@ -719,6 +719,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1539,
 /**/
     1538,
 /**/