SQLAlchemy 1.4.x: RootTransaction object cannot serve as stash storage for original method references

The 1.4 major release of sqlalchemy seems to introduce some interface changes that pytest-flask-sqlalchemy 1.0.2 has trouble handling.

In particular one case is that pytest-flask-sqlalchemy will attempt to store a transaction’s original rollback method in a temporary / ephemeral force_rollback property, but the current sqlalchemy 1.4.0 release seems incompatible with this – I think because the RootTransaction class defines an explicit list of slots available on the object.

This issue might be a one-off, or it could be part of a larger category of sqlalchemy 1.4 compatibility concerns.

[itajaja]

@jace we quite successfully dropped this package and we wrote our own fixture. this is the code, you might need to adapt it slightly for your needs

@pytest.fixture(autouse=True)
def enable_transactional_tests(db, connection):
    transaction = connection.begin()
    db.session = db.create_scoped_session(options={"bind": connection, "binds": {}})
    db.session.begin_nested()

    # for handling tests that actually call "session.rollback()"
    # https://docs.sqlalchemy.org/en/13/orm/session_transaction.html#joining-a-session-into-an-external-transaction-such-as-for-test-suites
    @event.listens_for(db.session, "after_transaction_end")
    def restart_savepoint(session, transaction_in):
        if transaction_in.nested and not transaction_in._parent.nested:
            session.expire_all()
            session.begin_nested()

    yield

    db.session.close()
    transaction.rollback()

where the db fixture is the db and the connection fixture is

@pytest.fixture(scope="session")
def connection(db):
    return db.engine.connect()

[jtfidje]

Here’s one I just had to deal with.

Whenever I use the db_session fixture this error is thrown:

AttributeError: 'RootTransaction' object has no attribute 'force_rollback'

... /site-packages/pytest_flask_sqlalchemy/fixtures.py:43: AttributeError

I’ve had to roll-back to SQLAlchemy v.1.3.24