MySQL Bugs: #79235: JSON_UNQUOTE() does not recognize unicode codes

Bug #79235	JSON_UNQUOTE() does not recognize unicode codes
Submitted:	11 Nov 2015 15:09	Modified:	17 Nov 2015 17:49
Reporter:	Georgi Kodinov	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Server: Documentation	Severity:	S2 (Serious)
Version:	5.7+	OS:	Any
Assigned to:	Jon Stephens	CPU Architecture:	Any

Description:
http://dev.mysql.com/doc/refman/5.7/en/json-modification-functions.html#function_json-unqu... says that "\uXXXX" should be recognized as "UTF-8 bytes for Unicode value XXXX".

In practice this does not happen. The rest of the escapes work, e.g. \t.

How to repeat:
mysql> select JSON_UNQUOTE('[ "\t\u0031" ]');
+--------------------------------+
| JSON_UNQUOTE('[ "\t\u0031" ]') |
+--------------------------------+
| [ "   u0031" ]                   |
+--------------------------------+
1 row in set (0.00 sec)

Suggested fix:
make it work ?

Thank you for the bug report.

I think this works as intended. The specification of JSON_UNQUOTE in WL#7909 says: "Returns textValue untouched if textValue does not start and end with double-quotes." Since the input string in the bug description does not start and end with double-quotes, it is correct to return it as it is. The documentation could be improved to state this explicitly.

Note that the expansion of \t in the example above is not performed by JSON_UNQUOTE, but rather of the SQL parser. Unless the NO_BACKSLASH_ESCAPES SQL mode is enabled, one needs to have double backslashes in the (SQL) string literal. The following works:

mysql> select JSON_UNQUOTE('"\\t\\u0031"');
+------------------------------+
| JSON_UNQUOTE('"\\t\\u0031"') |
+------------------------------+
| 	1                           |
+------------------------------+
1 row in set (0,00 sec)

Alternatively:

mysql> set sql_mode=NO_BACKSLASH_ESCAPES;
Query OK, 0 rows affected, 1 warning (0,00 sec)

mysql> select JSON_UNQUOTE('"\t\u0031"');
+----------------------------+
| JSON_UNQUOTE('"\t\u0031"') |
+----------------------------+
| 	1                         |
+----------------------------+
1 row in set (0,00 sec)

Posted by developer:
 
Changing to documentation bug.

Thank you for your bug report. This issue has been addressed in the documentation. The updated documentation will appear on our website shortly.