MySQL Bugs: #86454: Workbench can't process utf8mb4 encode

Bug #86454	Workbench can't process utf8mb4 encode
Submitted:	25 May 2017 7:34	Modified:	16 May 2018 19:18
Reporter:	yitao Xu	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Workbench	Severity:	S2 (Serious)
Version:	6.3.9	OS:	Windows (commercial version)
Assigned to:		CPU Architecture:	Any
Tags:	collation, utf8mb4, workbench

Description:
When character set utf8mb4, execute“select 'ア';”  an error code was reported.
"Error Code: 0 Server sent unknown charsetnr (255) . Please report"

'ア' is a Japanese katakana.

MySQL server :8.0.2-dmr-enterprise-commercial-advanced-log

How to repeat:
In workbench editor, execute below SQL:

set NAMES utf8mb4;
select 'ア';
Error Code: 0 Server sent unknown charsetnr (255) . Please report

In mysql client, execute the same SQL：

mysql> set NAMES utf8mb4;
Query OK, 0 rows affected (0.00 sec)

mysql> select 'ア';
+-----+
| ア  |
+-----+
| ア  |
+-----+
1 row in set (0.00 sec)

mysql>

if execute below SQL in Workbench, result is good.
set NAMES utf8;
select 'ア';

Suggested fix:
Fix the bug, workbench don't know the character which has been set utf8mb4

Ia m no expert in Japanese, but I believe that tThis particular character is a 3-byte UTF8 character, so utf8(mb3) and utf8mb4 shold make no difference. 

In SQLyog using the font "courier new" it works fine:
SET NAMES utf8; -- or "SET NAMES utf8mb4;" - it doesnt matter  
SELECT 'ア'; -- returns 'ア 
SELECT HEX('ア'); -- returns 'E382A2' - note here 3 bytes only

It may be a font problem you are facing. What exactly does WB display for you? You can attach a screenshot. 

-- Peter
-- not an Oracle/MySqL person.

OK, it displays an error.  I missed that.

select 'ア'

Attachment: utf8mb4.png (image/png, text), 86.05 KiB.

When connected with 8.0

Attachment: mb4.png (image/png, text), 181.99 KiB.

Thank you for the bug report. This only happens when connected with server 8.0.X.

Maybe it could be a Connector/C++ issue?

Thank you for verified it.
For this bug,execute 
"
set NAMES utf8mb4;
select 'a';
"
also get the same error.

If you think this is maybe a connector C++ issue, could you report it or provide  me some evidence or hint, I can report the problem.

Posted by developer:
 
Fixed as of the upcoming MySQL Workbench 8.0.12 release, and here's the changelog entry:

The SQL editor returned an error when valid characters were used with the
utf8mb4 character set.

Thank you for the bug report.