backends.base.test_operations.DatabaseOperationTests fails on MySQL in isolation

[Jon Dufresne]

When running the Django test backends.base.test_operations.DatabaseOperationTests in isolation with a MySQL configuration, it fails with the following error:

======================================================================
FAIL: test_window_frame_raise_not_supported_error (backends.base.test_operations.DatabaseOperationTests)
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Traceback (most recent call last):
  File ".../django/django/test/testcases.py", line 1114, in skip_wrapper
    if condition():
  File ".../django/django/test/testcases.py", line 1135, in <lambda>
    lambda: any(getattr(connection.features, feature, False) for feature in features),
  File ".../django/django/test/testcases.py", line 1135, in <genexpr>
    lambda: any(getattr(connection.features, feature, False) for feature in features),
  File ".../django/django/utils/functional.py", line 37, in __get__
    res = instance.__dict__[self.name] = self.func(instance)
  File ".../django/django/db/backends/mysql/features.py", line 84, in supports_over_clause
    if self.connection.mysql_is_mariadb:
  File ".../django/django/utils/functional.py", line 37, in __get__
    res = instance.__dict__[self.name] = self.func(instance)
  File ".../django/django/db/backends/mysql/base.py", line 344, in mysql_is_mariadb
    return 'mariadb' in self.mysql_server_info.lower()
  File ".../django/django/utils/functional.py", line 37, in __get__
    res = instance.__dict__[self.name] = self.func(instance)
  File ".../django/django/db/backends/mysql/base.py", line 330, in mysql_server_info
    with self.temporary_connection() as cursor:
  File "/usr/lib64/python3.7/contextlib.py", line 112, in __enter__
    return next(self.gen)
  File ".../django/django/db/backends/base/base.py", line 577, in temporary_connection
    with self.cursor() as cursor:
  File ".../django/django/test/testcases.py", line 144, in __call__
    "set %s.allow_database_queries to True to silence this failure." % self.cls_name
AssertionError: Database queries aren't allowed in SimpleTestCase. Either use TestCase or TransactionTestCase to ensure proper test isolation or set DatabaseOperationTests.allow_database_queries to True to silence this failure.

The test is using SimpleTestCase, but this test executes a query on MySQL for feature detection.

[Jon Dufresne]

​PR

[Tim Graham <timograham@…>]

In f0759305:

[2.1.x] Fixed #29813 -- Fixed DatabaseOperation test when run in isolation on MySQL.

Backport of 7598cd4748dc402b0209e5eedb6d2a83c3da1620 from master.

[Tim Graham <timograham@…>]

In 7598cd47:

Fixed #29813 -- Fixed DatabaseOperation test when run in isolation on MySQL.