patch 9.1.1127: preinsert text is not cleaned up correctly

Problem:  when 'completeopt' is set to preinsert the preinserted text is
          not cleared when adding new leader (Yee Cheng Chin)
Solution: add a condition to delete preinsert text in edit function
          (glepnir)

closes: #16672

Signed-off-by: glepnir <glephunter@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

src/edit.c

@@ -146,6 +146,7 @@ edit(
 #ifdef FEAT_CONCEAL
     int		cursor_line_was_concealed;
 #endif
+    int		ins_completion = FALSE;
 
     // Remember whether editing was restarted after CTRL-O.
     did_restart_edit = restart_edit;
@@ -636,10 +637,11 @@ edit(
 	 * and the cursor is still in the completed word.  Only when there is
 	 * a match, skip this when no matches were found.
 	 */
-	if (ins_compl_active()
-		&& pum_wanted()
-		&& curwin->w_cursor.col >= ins_compl_col()
-		&& ins_compl_has_shown_match())
+	ins_completion = ins_compl_active()
+	    && curwin->w_cursor.col >= ins_compl_col()
+	    && ins_compl_has_shown_match();
+
+	if (ins_completion && pum_wanted())
 	{
 	    // BS: Delete one character from "compl_leader".
 	    if ((c == K_BS || c == Ctrl_H)
@@ -697,6 +699,8 @@ edit(
 		    ins_compl_delete();
 	    }
 	}
+	else if (ins_completion && !pum_wanted() && ins_compl_preinsert_effect())
+	    ins_compl_delete();
 
 	// Prepare for or stop CTRL-X mode.  This doesn't do completion, but
 	// it does fix up the text when finishing completion.

src/testdir/test_ins_complete.vim

@@ -3171,6 +3171,11 @@ function Test_completeopt_preinsert()
   call assert_equal("fobar", getline('.'))
   call assert_equal(5, col('.'))
 
+  set cot=preinsert
+  call feedkeys("Sfoo1 foo2\<CR>f\<C-X>\<C-N>bar", 'tx')
+  call assert_equal("fbar", getline('.'))
+  call assert_equal(4, col('.'))
+
   bw!
   set cot&
   set omnifunc&

src/version.c

@@ -704,6 +704,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1127,
 /**/
     1126,
 /**/