When run test with off postgres database got `RuntimeError: generator didn't yield` instead of connection error

[Kazantcev Andrey]

I have only default database configuration and if I run tests without started postgresql I got

  File "C:\Users\Asus\.virtualenvs\curds-cxXQlVO3\lib\site-packages\django\test\runner.py", line 695, in run_tests
    old_config = self.setup_databases(aliases=databases)
  File "C:\Users\Asus\.virtualenvs\curds-cxXQlVO3\lib\site-packages\django\test\runner.py", line 614, in setup_databases
    return _setup_databases(
  File "C:\Users\Asus\.virtualenvs\curds-cxXQlVO3\lib\site-packages\django\test\utils.py", line 170, in setup_databases
    connection.creation.create_test_db(
  File "C:\Users\Asus\.virtualenvs\curds-cxXQlVO3\lib\site-packages\django\db\backends\base\creation.py", line 55, in create_test_db
    self._create_test_db(verbosity, autoclobber, keepdb)
  File "C:\Users\Asus\.virtualenvs\curds-cxXQlVO3\lib\site-packages\django\db\backends\base\creation.py", line 186, in _create_test_db
    with self._nodb_cursor() as cursor:
  File "c:\python39\lib\contextlib.py", line 119, in __enter__
    raise RuntimeError("generator didn't yield") from None
RuntimeError: generator didn't yield

Seams _nodb_cursor method didn't do yield when handling error.

[Mariusz Felisiak]

Thanks for the report, however the builtin django.db.backends.postgresql backend (on Python 3.9.0+ and 3.8.5) raises Connection refused for me (as expected):

django.db.utils.OperationalError: could not connect to server: Connection refused
        Is the server running on host "localhost" (127.0.0.1) and accepting
        TCP/IP connections on port 5432?

Can you share more details or a database configuration?

[Kazantcev Andrey]

Replying to Mariusz Felisiak:

Can you share more details or a database configuration?

Configuration

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.postgresql_psycopg2',
        'NAME': os.getenv('POSTGRESQL_NAME', 'postgres'),
        'USER': os.getenv('POSTGRESQL_USER', 'postgres'),
        'PASSWORD': os.getenv('POSTGRESQL_PASSWORD', 'postgres'),
        'HOST': os.getenv('POSTGRESQL_HOST', 'localhost'),
        'PORT': os.getenv('POSTGRESQL_PORT', '5432'),
        'OPTIONS': json.loads(os.getenv('POSTGRESQL_ENGINE_OPTIONS', '{}'))
    }
}

No specific database env vars sets. Used only default values.

I found a problem. The problem is in [these lines](​https://github.com/django/django/blob/f9cfd346f0222d86bfbac26ef5455806965bae6b/django/db/backends/postgresql/base.py#L324-L325). If I have one connection and test expression in if return false then function just return without reraise exception. And contextmanager raises error RuntimeError: generator didn't yield

Also, if I have more than two connection configurations with different NAME, this code will try to process only one next configuration, and if it is incorrect, it will throw an exception without trying to check the next connection.

[Tim Graham]

I've ​also seen this with django_cockroachdb (which inherits the PostgreSQL backend).

[Simon Charette]

Seems like a regression in f48f671223a20b161ca819cf7d6298e43b8ba5fe which is also part of 3.1.

[Mariusz Felisiak]

Thanks for details, I can confirm that it's a regression in f48f671223a20b161ca819cf7d6298e43b8ba5fe.

[Mariusz Felisiak]

​PR

[GitHub <noreply@…>]

In f131841c:

Fixed #32403 -- Fixed re-raising DatabaseErrors when using only 'postgres' database.

Thanks Kazantcev Andrey for the report.

Regression in f48f671223a20b161ca819cf7d6298e43b8ba5fe.

[Mariusz Felisiak <felisiak.mariusz@…>]

In 7d658893:

[3.2.x] Fixed #32403 -- Fixed re-raising DatabaseErrors when using only 'postgres' database.

Thanks Kazantcev Andrey for the report.

Regression in f48f671223a20b161ca819cf7d6298e43b8ba5fe.
Backport of f131841c601b9d4884adcdb284b4213c2ad89231 from master

[Mariusz Felisiak <felisiak.mariusz@…>]

In 9efe832e:

[3.1.x] Fixed #32403 -- Fixed re-raising DatabaseErrors when using only 'postgres' database.

Thanks Kazantcev Andrey for the report.

Regression in f48f671223a20b161ca819cf7d6298e43b8ba5fe.
Backport of f131841c601b9d4884adcdb284b4213c2ad89231 from master