TypeError creating DB table SQL with ExclusionConstraint as Statement returned instead of str

[James Beith]

Whilst upgrading from Django 4.0.7 to 4.1 we've hit an exception attempting to run our test suit.

We have some models with Postgres ExclusionConstraint constraints. When these constraints constraint_sql() is called ​here as part of building the test database, a Statement ​object is returned, instead of a str, and we crash when attempting to join them ​here

Looks like the ExclusionConstraint switched to returning a Statement instead of a str in ​this PR #15235.

Stacktrace below if it helps.

../../../../.virtualenvs/acme-corp/lib/python3.8/site-packages/pytest_django/plugin.py:465: in _django_db_marker
    request.getfixturevalue("_django_db_helper")
src/tests/conftest.py:966: in django_db_setup
    db_cfg = setup_databases(
../../../../.virtualenvs/acme-corp/lib/python3.8/site-packages/django/test/utils.py:220: in setup_databases
    connection.creation.create_test_db(
../../../../.virtualenvs/acme-corp/lib/python3.8/site-packages/django/db/backends/base/creation.py:78: in create_test_db
    call_command(
../../../../.virtualenvs/acme-corp/lib/python3.8/site-packages/django/core/management/__init__.py:198: in call_command
    return command.execute(*args, **defaults)
src/acme-corp/interfaces/common/management_commands.py:50: in execute
    return super().execute(*args, **options)
../../../../.virtualenvs/acme-corp/lib/python3.8/site-packages/django/core/management/base.py:448: in execute
    output = self.handle(*args, **options)
src/acme-corp/interfaces/systemjobs/management/commands/migrate.py:31: in handle
    super().handle(*args, **options)
../../../../.virtualenvs/acme-corp/lib/python3.8/site-packages/pytest_django/fixtures.py:276: in handle
    return super().handle(*args, **kwargs)
../../../../.virtualenvs/acme-corp/lib/python3.8/site-packages/django/core/management/base.py:96: in wrapped
    res = handle_func(*args, **kwargs)
../../../../.virtualenvs/acme-corp/lib/python3.8/site-packages/django/core/management/commands/migrate.py:314: in handle
    self.sync_apps(connection, executor.loader.unmigrated_apps)
../../../../.virtualenvs/acme-corp/lib/python3.8/site-packages/django/core/management/commands/migrate.py:476: in sync_apps
    editor.create_model(model)
../../../../.virtualenvs/acme-corp/lib/python3.8/site-packages/django/db/backends/base/schema.py:446: in create_model
    sql, params = self.table_sql(model)
../../../../.virtualenvs/acme-corp/lib/python3.8/site-packages/django/db/backends/base/schema.py:272: in table_sql
    "definition": ", ".join(
E   TypeError: sequence item 9: expected str instance, Statement found

[Mariusz Felisiak]

Thanks for the report! Regression in 0e656c02fe945389246f0c08f51c6db4a0849bd2.

[Mariusz Felisiak]

Regression test.

[Mariusz Felisiak]

James, would you like to prepare a patch?

[James Beith]

Mariusz, how's this? Hopefully it's this straight forward.

​https://github.com/django/django/pull/16035

[Mariusz Felisiak <felisiak.mariusz@…>]

In 19e838da:

Fixed #33982 -- Fixed migrations crash when adding model with ExclusionConstraint.

Regression in 0e656c02fe945389246f0c08f51c6db4a0849bd2.

[Mariusz Felisiak <felisiak.mariusz@…>]

In 7ba9a448:

[4.1.x] Fixed #33982 -- Fixed migrations crash when adding model with ExclusionConstraint.

Regression in 0e656c02fe945389246f0c08f51c6db4a0849bd2.

Backport of 19e838daa8872ee29fbea0bc471c2a6443f26835 from main