Extra dot in cloned test database file names on SQLite when using --parallel.

[Christian Abbott]

When asking Django to create on-disk (instead of in-memory) sqlite cloned test databases by using the --parallel flag, the cloned file names are created as, e.g., "test_db_1..sqlite3", "test_db_2..sqlite3", etc. (with two dots instead of one).

If the specified test database name lacks any extension, e.g. just 'test_db', then the cloned file names have a trailing dot: "test_db_1.", "test_db_2.", "test_db_3.", etc.

This is due to this line:

​https://github.com/django/django/blob/main/django/db/backends/sqlite3/creation.py#L58

...in get_test_db_clone_settings() which constructs the file name using the string:

'{}_{}.{}'.format(root, suffix, ext)

However, os.path.splitext() already includes the dot in the returned extension ('ext'). Removing the dot from the format string seems the only change needed to fix it:

'{}_{}{}'.format(root, suffix, ext)

From the github file history it looks like this quirk has been there since the --parallel flag was first introduced (commit 0586c061f0b857e2259bea48e21ebb69a7878d13 in Sep 2015).

To reproduce the issue:

In settings.py, force on-disk instead of in-memory test databases by specifying any test db name:

DATABASES = {
    'default': {
        ENGINE: 'django.db.backends.sqlite3',
        NAME: 'db.sqlite3',
        TEST: {
            'NAME': test_db.sqlite3',
        }
    }
}

Create any model with migrations, and more than one TestCase class (to ensure --parallel creates clones of the test database).

And on the command line, run tests with --parallel and --keepdb to see the db files generated. This should be run on a multi-core processor.

manage.py test --parallel --keepdb

[Mariusz Felisiak]

Good catch, would you like to prepare a patch? (tests are required)

[Girish Sontakke]

Replying to Mariusz Felisiak:

Good catch, would you like to prepare a patch? (tests are required)

May I work on this patch.

[Girish Sontakke]

​https://github.com/django/django/pull/14169

[GitHub <noreply@…>]

In 5388ff2a:

Fixed #32582 -- Removed unnecessary dot in names of cloned test databases on SQLite.