Add warnings count for non-DML/DLL queries like SELECT

[KunZhou-at]

Turns out SELECT queries can also produce warnings, for example:

mysql> SELECT STR_TO_DATE("asdfasdfasdf", "%m-%d-%Y %H:%i:%s");
+--------------------------------------------------+
| STR_TO_DATE("asdfasdfasdf", "%m-%d-%Y %H:%i:%s") |
+--------------------------------------------------+
| NULL                                             |
+--------------------------------------------------+
1 row in set, 1 warning (0.00 sec)

mysql> show warnings;
+---------+------+-------------------------------------------------------------------+
| Level   | Code | Message                                                           |
+---------+------+-------------------------------------------------------------------+
| Warning | 1411 | Incorrect datetime value: 'asdfasdfasdf' for function str_to_date |
+---------+------+-------------------------------------------------------------------+
1 row in set (0.00 sec)

This change adds the warnings count from the second EOF packet for a SELECT query (reference here) because I don't think it's possible for the first EOF packet, the one following FIELDS, to have warnings.

[wellwelwel]

@KunZhou-at, using this approach in practice with promise, would it be something like [rows, fields, warnings] = await conn.query(...)?

[KunZhou-at]

@wellwelwel Yeah, in terms of the API it might be a little confusing that DMLs have their warning counts as the first returned value but it's the last returned value for SELECTs.

[wellwelwel]

Thanks, @KunZhou-at. In this case, I'm only focusing on typings 🙋🏻‍♂️

You've changed the query callback types:

- | ((err: QueryError | null, result: T, fields: FieldPacket[]) => any)
+ | ((err: QueryError | null, result: T, fields: FieldPacket[], warningCount: number | number[]) => any)

So I wonder if it can also be done in execute.

Also, for promises:

- Promise<[T, FieldPacket[]]>;
+ Promise<[T, FieldPacket[], warningCount: number | number[]]>;