patch 9.1.1880: Allocation error with complete_info()

Problem:  Allocation error with complete_info()
          (after v9.1.1876)
Solution: Make sure length is positive (kuuote)

closes: #18640

Signed-off-by: kuuote <znmxodq1@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

Author: kuuote

src/insexpand.c

@@ -4235,7 +4235,7 @@ get_complete_info(list_T *what_list, dict_T *retdict)
 	int	len = compl_ins_end_col - curwin->w_cursor.col;
 
 	ret = dict_add_string_len(retdict, "preinserted_text",
-		(len > 0) ? line + curwin->w_cursor.col : (char_u *)"", len);
+		(len > 0) ? line + curwin->w_cursor.col : (char_u *)"", (len > 0) ? len : 0);
     }
 
     if (ret == OK && (what_flag & (CI_WHAT_ITEMS | CI_WHAT_SELECTED

src/testdir/test_ins_complete.vim

@@ -571,6 +571,10 @@ func Test_completefunc_info()
   new
   set completeopt=menuone
   set completefunc=CompleteTest
+    " Can be called outside of ins-completion
+  call feedkeys("i\<C-X>\<C-U>\<C-Y>\<C-R>\<C-R>=string(complete_info())\<CR>\<ESC>", "tx")
+  call assert_equal("matched{'preinserted_text': '', 'pum_visible': 0, 'mode': '', 'selected': -1, 'items': []}", getline(1))
+  %d
   call feedkeys("i\<C-X>\<C-U>\<C-R>\<C-R>=string(complete_info())\<CR>\<ESC>", "tx")
   call assert_equal("matched{'preinserted_text': '', 'pum_visible': 1, 'mode': 'function', 'selected': 0, 'items': [{'word': 'matched', 'menu': '', 'user_data': '', 'info': '', 'kind': '', 'abbr': ''}]}", getline(1))
   %d

src/version.c

@@ -729,6 +729,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1880,
 /**/
     1879,
 /**/