batch auto mode stops checking directives after add_column()

[mfmarche]

Describe the bug
In a batch alter_table, a column is added and a unique_constraint is added. In version 1.6.5, this worked as expected, but the recent 1.7.0 update now gives:

"NotImplementedError: No support for ALTER of constraints in SQLite dialectPlease refer to the batch mode feature which allows for SQLite migrations using a copy-and-move strategy."

Expected behavior
I believe it is related to the recent change here: e34f6c1

I don't believe any changes to the migration are necessary based on the documented behavior changes that commit suggested.

To Reproduce

    with op.batch_alter_table("table") as batch_op:
        batch_op.add_column(sa.Column("a", sa.String(length=20), nullable=True))
        batch_op.create_unique_constraint(
            "uq", ["a", "b"]
        )

Error

alembic/versions/391853fcf800_connector_slug.py:22: in upgrade
    batch_op.create_unique_constraint(
/usr/lib/python3.8/contextlib.py:120: in __exit__
    next(self.gen)
../../../.cache/pypoetry/virtualenvs/app-db-PYu9--OD-py3.8/lib/python3.8/site-packages/alembic/operations/base.py:369: in batch_alter_table
    impl.flush()
../../../.cache/pypoetry/virtualenvs/app-db-PYu9--OD-py3.8/lib/python3.8/site-packages/alembic/operations/batch.py:107: in flush
    fn(*arg, **kw)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

self = <alembic.ddl.sqlite.SQLiteImpl object at 0x7f3046e44e20>, const = UniqueConstraint(Column('name_slug', NullType(), table=<connector>), Column('org_id', NullType(), table=<connector>))

    def add_constraint(self, const: "Constraint"):
        # attempt to distinguish between an
        # auto-gen constraint and an explicit one
        if const._create_rule is None:  # type:ignore[attr-defined]
>           raise NotImplementedError(
                "No support for ALTER of constraints in SQLite dialect"
                "Please refer to the batch mode feature which allows for "
                "SQLite migrations using a copy-and-move strategy."
E               NotImplementedError: No support for ALTER of constraints in SQLite dialectPlease refer to the batch mode feature which allows for SQLite migrations using a copy-and-move strategy.

Versions.

• OS: Ubuntu 20.04.2
• Python: 3.8
• Alembic: 1.7.0
• SQLAlchemy: 1.3.24
• Database: sqlite

Additional context

Have a nice day!

[zzzeek]

mmm nope that change did not affect this, the change is this one: 3110acb

force batch mode to "always" to work around:

with op.batch_alter_table("table", recreate="always") 

[sqla-tester]

Mike Bayer has proposed a fix for this issue in the master branch:

check all directives in batch block until recreate selected https://gerrit.sqlalchemy.org/c/sqlalchemy/alembic/+/3034