[Sqlalchemy-tickets] Issue #3817: Explicit naming convention error on upgrade to 1.1 on alembic migrate (zzzeek/sqlalchemy)

[Dave M. <iss...@bi...>]

New issue 3817: Explicit naming convention error on upgrade to 1.1 on alembic migrate
https://bitbucket.org/zzzeek/sqlalchemy/issues/3817/explicit-naming-convention-error-on

Dave McDaniel:

After today's update to 1.1 I am now getting a migration error with the following traceback:

```bash
  File "/home/dave/Code/edgar/alembic/versions/c3337510cab5_added_signing_table.py", line 20, in upgrade
    globals()["upgrade_%s" % engine_name]()
  File "/home/dave/Code/edgar/alembic/versions/c3337510cab5_added_signing_table.py", line 51, in upgrade_main_db
    ['signing_id'], ['id'])
  File "/usr/lib/python3.4/contextlib.py", line 66, in __exit__
    next(self.gen)
  File "/usr/lib/python3.4/site-packages/alembic/operations/base.py", line 299, in batch_alter_table
    impl.flush()
  File "/usr/lib/python3.4/site-packages/alembic/operations/batch.py", line 73, in flush
    *self.reflect_args, **self.reflect_kwargs)
  File "/usr/lib/python3.4/site-packages/sqlalchemy/sql/schema.py", line 436, in __new__
    metadata._remove_table(name, schema)
  File "/usr/lib/python3.4/site-packages/sqlalchemy/util/langhelpers.py", line 60, in __exit__
    compat.reraise(exc_type, exc_value, exc_tb)
  File "/usr/lib/python3.4/site-packages/sqlalchemy/util/compat.py", line 186, in reraise
    raise value
  File "/usr/lib/python3.4/site-packages/sqlalchemy/sql/schema.py", line 431, in __new__
    table._init(name, metadata, *args, **kw)
  File "/usr/lib/python3.4/site-packages/sqlalchemy/sql/schema.py", line 507, in _init
    self._autoload(metadata, autoload_with, include_columns)
  File "/usr/lib/python3.4/site-packages/sqlalchemy/sql/schema.py", line 519, in _autoload
    self, include_columns, exclude_columns
  File "/usr/lib/python3.4/site-packages/sqlalchemy/engine/base.py", line 1528, in run_callable
    return callable_(self, *args, **kwargs)
  File "/usr/lib/python3.4/site-packages/sqlalchemy/engine/default.py", line 364, in reflecttable
    return insp.reflecttable(table, include_columns, exclude_columns)
  File "/usr/lib/python3.4/site-packages/sqlalchemy/engine/reflection.py", line 605, in reflecttable
    exclude_columns, reflection_options)
  File "/usr/lib/python3.4/site-packages/sqlalchemy/engine/reflection.py", line 727, in _reflect_fk
    **reflection_options
  File "/usr/lib/python3.4/site-packages/sqlalchemy/sql/schema.py", line 436, in __new__
    metadata._remove_table(name, schema)
  File "/usr/lib/python3.4/site-packages/sqlalchemy/util/langhelpers.py", line 60, in __exit__
    compat.reraise(exc_type, exc_value, exc_tb)
  File "/usr/lib/python3.4/site-packages/sqlalchemy/util/compat.py", line 186, in reraise
    raise value
  File "/usr/lib/python3.4/site-packages/sqlalchemy/sql/schema.py", line 431, in __new__
    table._init(name, metadata, *args, **kw)
  File "/usr/lib/python3.4/site-packages/sqlalchemy/sql/schema.py", line 507, in _init
    self._autoload(metadata, autoload_with, include_columns)
  File "/usr/lib/python3.4/site-packages/sqlalchemy/sql/schema.py", line 519, in _autoload
    self, include_columns, exclude_columns
  File "/usr/lib/python3.4/site-packages/sqlalchemy/engine/base.py", line 1528, in run_callable
    return callable_(self, *args, **kwargs)
  File "/usr/lib/python3.4/site-packages/sqlalchemy/engine/default.py", line 364, in reflecttable
    return insp.reflecttable(table, include_columns, exclude_columns)
  File "/usr/lib/python3.4/site-packages/sqlalchemy/engine/reflection.py", line 617, in reflecttable
    include_columns, exclude_columns, reflection_options)
  File "/usr/lib/python3.4/site-packages/sqlalchemy/engine/reflection.py", line 833, in _reflect_check_constraints
    sa_schema.CheckConstraint(**const_d))
  File "/usr/lib/python3.4/site-packages/sqlalchemy/sql/schema.py", line 688, in append_constraint
    constraint._set_parent_with_dispatch(self)
  File "/usr/lib/python3.4/site-packages/sqlalchemy/sql/base.py", line 434, in _set_parent_with_dispatch
    self.dispatch.after_parent_attach(self, parent)
  File "/usr/lib/python3.4/site-packages/sqlalchemy/event/attr.py", line 218, in __call__
    fn(*args, **kw)
  File "/usr/lib/python3.4/site-packages/sqlalchemy/sql/naming.py", line 144, in _constraint_name
    newname = _constraint_name_for_table(const, table)
  File "/usr/lib/python3.4/site-packages/sqlalchemy/sql/naming.py", line 124, in _constraint_name_for_table
    metadata.naming_convention)
  File "/usr/lib/python3.4/site-packages/sqlalchemy/sql/naming.py", line 79, in __getitem__
    return getattr(self, '_key_%s' % key)()
  File "/usr/lib/python3.4/site-packages/sqlalchemy/sql/naming.py", line 43, in _key_constraint_name
    "Naming convention including "
sqlalchemy.exc.InvalidRequestError: Naming convention including %(constraint_name)s token requires that constraint is explicitly named.
```

The odd thing is that the name is explicitly set in the  `create_foreign_key` call (line 51 as identified in the traceback), which is below:

```python
    with op.batch_alter_table('experiment', naming_convention=convention,
                              schema=None) as batch_op:
        batch_op.add_column(sa.Column('signing_id', sa.Integer(), nullable=True))
        batch_op.create_foreign_key(op.f('fk_experiment_signing_id_signing'),
                                    'signing',
                                    ['signing_id'], ['id'])
```

convention is defined as:

```python
convention = {
    "ix": 'ix_%(column_0_label)s',
    "uq": "uq_%(table_name)s_%(column_0_name)s",
    "ck": "ck_%(table_name)s_%(constraint_name)s",
    "fk": "fk_%(table_name)s_%(column_0_name)s_%(referred_table_name)s",
    "pk": "pk_%(table_name)s"
}
```

Based on alembic docs, the first postional argument to `create_foreign_key` is the `constraint_name`, so I don't understand the traceback message that it is not being defined, as it is in the call via that first positional argument.