Make order of 'info' in completion_info consistent

Start the iteration from the same point and follow the same direction as
done when assigning the completion numbers. This way we remove the
dependance on the completion direction and make the order of 'info'
consistent.

Fixes #12230

src/insexpand.c

@@ -3040,6 +3040,43 @@ ins_compl_update_sequence_numbers(void)
     }
 }
 
+    static int
+info_add_completion_info(list_T *li)
+{
+    compl_T	*match;
+
+    if (compl_first_match == NULL)
+	return OK;
+
+    // Skip the element with the CP_ORIGINAL_TEXT flag at the beginning, in case of
+    // forward completion, or at the end, in case of backward completion.
+    match = compl_dir_forward()
+	    ? compl_first_match->cp_next : compl_first_match->cp_prev->cp_prev;
+    while (match != NULL && !match_at_original_text(match))
+    {
+	dict_T *di = dict_alloc();
+
+	if (di == NULL)
+	    return FAIL;
+	if (list_append_dict(li, di) == FAIL)
+	    return FAIL;
+	dict_add_string(di, "word", match->cp_str);
+	dict_add_string(di, "abbr", match->cp_text[CPT_ABBR]);
+	dict_add_string(di, "menu", match->cp_text[CPT_MENU]);
+	dict_add_string(di, "kind", match->cp_text[CPT_KIND]);
+	dict_add_string(di, "info", match->cp_text[CPT_INFO]);
+	if (match->cp_user_data.v_type == VAR_UNKNOWN)
+	    // Add an empty string for backwards compatibility
+	    dict_add_string(di, "user_data", (char_u *)"");
+	else
+	    dict_add_tv(di, "user_data", &match->cp_user_data);
+
+	match = compl_dir_forward() ? match->cp_next : match->cp_prev;
+    }
+
+    return OK;
+}
+
 /*
  * Get complete information
  */
@@ -3088,41 +3125,13 @@ get_complete_info(list_T *what_list, dict_T *retdict)
     if (ret == OK && (what_flag & CI_WHAT_ITEMS))
     {
 	list_T	    *li;
-	dict_T	    *di;
-	compl_T     *match;
 
 	li = list_alloc();
 	if (li == NULL)
 	    return;
 	ret = dict_add_list(retdict, "items", li);
-	if (ret == OK && compl_first_match != NULL)
-	{
-	    match = compl_first_match;
-	    do
-	    {
-		if (!match_at_original_text(match))
-		{
-		    di = dict_alloc();
-		    if (di == NULL)
-			return;
-		    ret = list_append_dict(li, di);
-		    if (ret != OK)
-			return;
-		    dict_add_string(di, "word", match->cp_str);
-		    dict_add_string(di, "abbr", match->cp_text[CPT_ABBR]);
-		    dict_add_string(di, "menu", match->cp_text[CPT_MENU]);
-		    dict_add_string(di, "kind", match->cp_text[CPT_KIND]);
-		    dict_add_string(di, "info", match->cp_text[CPT_INFO]);
-		    if (match->cp_user_data.v_type == VAR_UNKNOWN)
-			// Add an empty string for backwards compatibility
-			dict_add_string(di, "user_data", (char_u *)"");
-		    else
-			dict_add_tv(di, "user_data", &match->cp_user_data);
-		}
-		match = match->cp_next;
-	    }
-	    while (match != NULL && !is_first_match(match));
-	}
+	if (ret == OK)
+	    ret = info_add_completion_info(li);
     }
 
     if (ret == OK && (what_flag & CI_WHAT_SELECTED))

src/testdir/test_ins_complete.vim

@@ -2243,5 +2243,43 @@ func Test_ins_complete_popup_position()
   call StopVimInTerminal(buf)
 endfunc
 
+func GetCompleteInfo()
+  let g:compl_info = complete_info()
+  return ''
+endfunc
+
+func Test_complete_info_index()
+  new
+  call setline(1, ["aaa", "bbb", "ccc", "ddd", "eee", "fff"])
+  inoremap <buffer><F5> <C-R>=GetCompleteInfo()<CR>
+
+  " Ensure 'index' in complete_info() is coherent with the 'items' array.
+
+  set completeopt=menu,preview
+  " Search forward.
+  call feedkeys("Go\<C-X>\<C-N>\<F5>\<Esc>_dd", 'tx')
+  call assert_equal("aaa", g:compl_info['items'][g:compl_info['selected']]['word'])
+  call feedkeys("Go\<C-X>\<C-N>\<C-N>\<F5>\<Esc>_dd", 'tx')
+  call assert_equal("bbb", g:compl_info['items'][g:compl_info['selected']]['word'])
+
+  " Search backward.
+  call feedkeys("Go\<C-X>\<C-P>\<F5>\<Esc>_dd", 'tx')
+  call assert_equal("fff", g:compl_info['items'][g:compl_info['selected']]['word'])
+  call feedkeys("Go\<C-X>\<C-P>\<C-P>\<F5>\<Esc>_dd", 'tx')
+  call assert_equal("eee", g:compl_info['items'][g:compl_info['selected']]['word'])
+
+  " Add 'noselect', check that 'selected' is -1 when nothing is selected.
+  set completeopt+=noselect
+  " Search forward.
+  call feedkeys("Go\<C-X>\<C-N>\<F5>\<Esc>_dd", 'tx')
+  call assert_equal(-1, g:compl_info['selected'])
+
+  " Search backward.
+  call feedkeys("Go\<C-X>\<C-P>\<F5>\<Esc>_dd", 'tx')
+  call assert_equal(-1, g:compl_info['selected'])
+
+  set completeopt&
+  bwipe!
+endfunc
 
 " vim: shiftwidth=2 sts=2 expandtab