[Sqlalchemy-tickets] Issue #4277: mysql dialects client_flags work inconsistently per calling style (zzzeek/sqlalchemy)

[Michael B. <iss...@bi...>]

New issue 4277: mysql dialects client_flags work inconsistently per calling style
https://bitbucket.org/zzzeek/sqlalchemy/issues/4277/mysql-dialects-client_flags-work

Michael Bayer:

because the dialects apply the FOUND_ROWS inside the create_connect_args method, if client_flags are passed in connect_args, the FOUND_ROWS flag is not applied:

```
#!python


from sqlalchemy import create_engine
from MySQLdb.constants import CLIENT
from unittest import mock

from MySQLdb import connect
m1 = mock.Mock()

def patch_mysql_connect(*arg, **kw):
    m1(*arg, **kw)
    return connect(*arg, **kw)

with mock.patch("MySQLdb.connect", patch_mysql_connect):
    e1 = create_engine(
        "mysql+mysqldb://scott:tiger@localhost/test?client_flag=%s" %
        CLIENT.MULTI_STATEMENTS,
    )

    e2 = create_engine(
        "mysql+mysqldb://scott:tiger@localhost/test",
        connect_args={"client_flag": CLIENT.MULTI_STATEMENTS}
    )

    c1 = e1.connect()
    c2 = e2.connect()

    print(m1.mock_calls)
    assert m1.mock_calls[0] == m1.mock_calls[1]

```

output


```
#!python

[call(client_flag=65538, db='test', host='localhost', passwd='tiger', user='scott'),
 call(client_flag=65536, db='test', host='localhost', passwd='tiger', user='scott')]
Traceback (most recent call last):
  File "test.py", line 27, in <module>
    assert m1.mock_calls[0] == m1.mock_calls[1]
AssertionError

```

we either need to change the API of create_connect_args to also accept the client arguments, which would break many third party dialects, pass them onto the URL, or add a new method so that the dialect gets access to the connect args.