MDEV-11571 JSON_EXTRACT returns wrong results.

        Array counter didn't increment after an item was found.

mysql-test/r/func_json.result

@@ -209,6 +209,9 @@ json_extract('[10, 20, [{"a":3}, 30, 40]]', '$[2][*]')
 select json_extract('1', '$');
 json_extract('1', '$')
 1
+select json_extract('[10, 20, [30, 40], 1, 10]', '$[1]');
+json_extract('[10, 20, [30, 40], 1, 10]', '$[1]')
+20
 select json_insert('{"a":1, "b":{"c":1}, "d":[1, 2]}', '$.b.k1', 'word');
 json_insert('{"a":1, "b":{"c":1}, "d":[1, 2]}', '$.b.k1', 'word')
 {"a":1, "b":{"c":1, "k1":"word"}, "d":[1, 2]}

mysql-test/t/func_json.test

@@ -77,6 +77,7 @@ select json_extract(json_object('foo', 'foobar'),'$');
 select json_extract('[10, 20, [30, 40]]', '$[2][*]');
 select json_extract('[10, 20, [{"a":3}, 30, 40]]', '$[2][*]');
 select json_extract('1', '$');
+select json_extract('[10, 20, [30, 40], 1, 10]', '$[1]');
 
 select json_insert('{"a":1, "b":{"c":1}, "d":[1, 2]}', '$.b.k1', 'word');
 select json_insert('{"a":1, "b":{"c":1}, "d":[1, 2]}', '$.d[3]', 3);

strings/json_lib.c

@@ -1270,7 +1270,7 @@ int json_find_path(json_engine_t *je,
     case JST_VALUE:
       DBUG_ASSERT(cur_step->type & JSON_PATH_ARRAY);
       if (cur_step->type & JSON_PATH_WILD ||
-          cur_step->n_item == array_counters[cur_step - p->steps])
+          cur_step->n_item == array_counters[cur_step - p->steps]++)
       {
         /* Array item matches. */
         if (cur_step == p->last_step ||
@@ -1278,10 +1278,7 @@ int json_find_path(json_engine_t *je,
           goto exit;
       }
       else
-      {
         json_skip_array_item(je);
-        array_counters[cur_step - p->steps]++;
-      }
       break;
     case JST_OBJ_END:
     case JST_ARRAY_END: