Add an option not to run migrations when running tests

[Kai Richard König]

With large apps it takes too long to run all migrations if you just want to run a single test or testcase. Furthermore keepdb is not an option if you already use an in memory sqlite db.

[Shai Berger]

See ​discussion and ​PR

[Shai Berger]

#24481 is very closely related (essentially, the same mechanism should be used to generate SQL statements. For #24481, they should be printed; here, executed).

[Andrew Godwin]

PR for this is up at ​https://github.com/django/django/pull/4986

[Tim Graham <timograham@…>]

In 04e69598:

Refs #24919 -- Made test models serializable for migrations.

[Tim Graham <timograham@…>]

In b60375d4:

Fixed #25129 -- Made model instance defaults work with migrations (refs #24919).

[Markus Holtermann]

@andrewgodwin what's your thought about ​https://github.com/django/django/pull/5255

[Tim Graham]

Added some ideas for improvement to the PR.

As I mentioned in IRC, it could also be useful to allow the DATABASES['TEST']['MIGRATE'] = False option that Andrew's first PR suggested to be a shortcut for setting MIGRATION_MODULES = {'a': None, 'b': None', ...} for all apps. This could be done later or in a separate commit though. The main concern I have with this idea is whether or not it makes sense in a multi-db situation.

[Markus Holtermann <info@…>]

In a3c01b0:

Fixed #24919 -- Allowed disabling of migrations on a per app basis

[Markus Holtermann <info@…>]

In f45ee197:

Refs #24919 -- Raised more helpful error message for disabled migrations

[Markus Holtermann]

Replying to timgraham:

Added some ideas for improvement to the PR.

As I mentioned in IRC, it could also be useful to allow the DATABASES['TEST']['MIGRATE'] = False option that Andrew's first PR suggested to be a shortcut for setting MIGRATION_MODULES = {'a': None, 'b': None', ...} for all apps. This could be done later or in a separate commit though. The main concern I have with this idea is whether or not it makes sense in a multi-db situation.

I created #25388 to keep track of this proposal if somebody wants to work on it.

[Simon Charette <charette.s@…>]

In 4dcaa587:

Fixed #26135 -- Adjusted the migration questioner's handling of disabled apps.

This was causing an issue when calling the migrate command in a test case with
the available_apps attribute pointing to an application with migrations
disabled using the MIGRATION_MODULES setting.

Thanks to Tim Graham for the review.

Refs #24919

[Simon Charette <charette.s@…>]

In 477274ac:

Refs #24919 -- Used the documented way of disabling migrations per app.

[Simon Charette <charette.s@…>]

In abdbf00:

[1.9.x] Fixed #26135 -- Adjusted the migration questioner's handling of disabled apps.

This was causing an issue when calling the migrate command in a test case with
the available_apps attribute pointing to an application with migrations
disabled using the MIGRATION_MODULES setting.

Thanks to Tim Graham for the review.

Refs #24919

Backport of 4dcaa5871b70859952c6f9c437dfe1b5f10509f2 from master

[Simon Charette <charette.s@…>]

In 645fddcd:

[1.9.x] Refs #24919 -- Used the documented way of disabling migrations per app.

Backport of 477274acb46b2f07666e9f84dea2e65ea6b63ad3 from master