implement JSON_QUOTE()

[jycor]

MySQL Docs:
https://dev.mysql.com/doc/refman/8.0/en/json-creation-functions.html#function_json-quote

[fulghum]

Code looks good, but I'm not sure that we're matching MySQL's behavior for JSON_QUOTE, particularly around escape chars.

[fulghum]

Should this be an error, same as the test case for json_unquote?

[jycor]

I'm not sure why json_unquote throws an error in the first place; I'm having trouble replicating in MySQL...

[fulghum]

Should this be escaping the backslashes in the control characters? It seems like MySQL doesn't return the same result. I'm not sure I totally understand what MySQL is doing here though... so I'm probably missing something. I don't get why it drops the \ in \u0032.

mysql> SELECT JSON_QUOTE('"\t\u0032"');
+--------------------------+
| JSON_QUOTE('"\t\u0032"') |
+--------------------------+
| "\"\tu0032\""            |
+--------------------------+

[jycor]

I believe this has something to do with the shell vs string literals?
When compiling and running dolt sql, I get the same output:

tmp/main>  SELECT JSON_QUOTE('"\t\u0032"');
+--------------------------+
| JSON_QUOTE('"\t\u0032"') |
+--------------------------+
| "\"\tu0032\""            |
+--------------------------+
1 row in set (0.00 sec)

[fulghum]

For this one, with MySQL, I'm getting:

mysql> select JSON_QUOTE('\b\f\n\r\t\"');
+----------------------------+
| JSON_QUOTE('\b\f\n\r\t\"') |
+----------------------------+
| "\bf\n\r\t\""              |
+----------------------------+

The MySQL docs call out that \f is a supported escape sequence, but it also says for non-supported escape sequences it ignores the \, which seems to be what it's doing here with \f.

[jycor]

Same as above

tmp/main> select json_quote("\b\f\n\r\t\"");
+----------------------------+
| json_quote("\b\f\n\r\t\"") |
+----------------------------+
| "\bf\n\r\t\""              |
+----------------------------+
1 row in set (0.00 sec)

[fulghum]

Thanks for confirming with the dolt sql examples. Looks good to me!