MDEV-30412: JSON_OBJECTAGG doesn't escape double quote in key

mysql-test/main/func_json.result

@@ -1623,5 +1623,17 @@ id	doc
 {"$oid":"611c0a463b150154132f6636"}	{ "_id" : { "$oid" : "611c0a463b150154132f6636" }, "a" : [ { "a" : [ { "a" : [ { "a" : [ { "a" : [ { "a" : [ { "a" : [ { "a" : [ { "a" : [ { "a" : [ { "a" : [ { "a" : [ { "a" : [ { "a" : [ { "a" : [ { "a" : 1.0 } ] } ] } ] } ] } ] } ] } ] } ] } ] } ] } ] } ] } ] } ] } ] }
 DROP TABLE arrNestTest;
 #
+# MDEV-30412 JSON_OBJECTAGG doesn't escape double quote in key
+#
+SELECT JSON_OBJECTAGG('"', 1);
+JSON_OBJECTAGG('"', 1)
+{"\"":1}
+SELECT JSON_OBJECTAGG('\"', 1);
+JSON_OBJECTAGG('\"', 1)
+{"\"":1}
+SELECT JSON_OBJECTAGG('\\', 1);
+JSON_OBJECTAGG('\\', 1)
+{"\\":1}
+#
 # End of 10.5 tests
 #

mysql-test/main/func_json.test

@@ -1067,6 +1067,14 @@ INSERT INTO test.arrNestTest (doc) VALUES ('{ "_id" : { "$oid" : "611c0a463b1501
 SELECT * FROM arrNestTest;
 DROP TABLE arrNestTest;
 
+--echo #
+--echo # MDEV-30412 JSON_OBJECTAGG doesn't escape double quote in key
+--echo #
+
+SELECT JSON_OBJECTAGG('"', 1);
+SELECT JSON_OBJECTAGG('\"', 1);
+SELECT JSON_OBJECTAGG('\\', 1);
+
 --echo #
 --echo # End of 10.5 tests
 --echo #

sql/item_jsonfunc.cc

@@ -4060,7 +4060,7 @@ bool Item_func_json_objectagg::add()
     result.append(", ");
 
   result.append("\"");
-  result.append(*key);
+  st_append_escaped(&result,key);
   result.append("\":");
 
   buf.length(0);