MDEV-38264: Fix failed assertion in json_find_path with trailing commas

mysql-test/main/func_json.result

@@ -2770,4 +2770,28 @@ S1A1
 SELECT JSON_VALUE('{"a":[1,2]}', '$.a[*]');
 JSON_VALUE('{"a":[1,2]}', '$.a[*]')
 NULL
+#
+# MDEV-38264 Assertion in json_find_path() fails after computing
+# array size of invalid json structure
+#
+SELECT JSON_QUERY('{ "A": [0,] }', '$.A[-1]');
+JSON_QUERY('{ "A": [0,] }', '$.A[-1]')
+NULL
+SELECT JSON_VALUE('{ "A": [0,] }', '$.A[-1]');
+JSON_VALUE('{ "A": [0,] }', '$.A[-1]')
+NULL
+SELECT JSON_VALUE('{ "A": [5,] }', '$.A[-2]');
+JSON_VALUE('{ "A": [5,] }', '$.A[-2]')
+NULL
+SELECT JSON_VALUE('{ "A": [5] }', '$.A[-2]');
+JSON_VALUE('{ "A": [5] }', '$.A[-2]')
+NULL
+SELECT JSON_LENGTH('{ "A": [0,] }', '$.A');
+JSON_LENGTH('{ "A": [0,] }', '$.A')
+NULL
+Warnings:
+Warning	4038	Syntax error in JSON text in argument 1 to function 'json_length' at position 11
+SELECT JSON_VALID('{ "A": [0,] }');
+JSON_VALID('{ "A": [0,] }')
+0
 # End of 10.11 Test

mysql-test/main/func_json.test

@@ -2032,4 +2032,16 @@ COLUMNS(NAME VARCHAR(30) PATH '$.NAME')) AS t_sz;
 
 SELECT JSON_VALUE('{"a":[1,2]}', '$.a[*]');
 
+--echo #
+--echo # MDEV-38264 Assertion in json_find_path() fails after computing
+--echo # array size of invalid json structure
+--echo #
+
+SELECT JSON_QUERY('{ "A": [0,] }', '$.A[-1]');
+SELECT JSON_VALUE('{ "A": [0,] }', '$.A[-1]');
+SELECT JSON_VALUE('{ "A": [5,] }', '$.A[-2]');
+SELECT JSON_VALUE('{ "A": [5] }', '$.A[-2]');
+SELECT JSON_LENGTH('{ "A": [0,] }', '$.A');
+SELECT JSON_VALID('{ "A": [0,] }');
+
 --echo # End of 10.11 Test

strings/json_lib.c

@@ -1306,9 +1306,13 @@ int json_skip_level_and_count(json_engine_t *j, int *n_items_skipped)
 int json_skip_array_and_count(json_engine_t *je, int *n_items)
 {
   json_engine_t j= *je;
+  int res;
   *n_items= 0;
 
-  return json_skip_level_and_count(&j, n_items); 
+  res= json_skip_level_and_count(&j, n_items);
+  if (res)
+    je->s.error= j.s.error;
+  return res;
 }