Add support for adding on_delete for ForeignKey and OneToOneField

[cvanderkolk]

Adding a feature to handle adding the on_delete argument to ForeignKey and OneToOneField types: https://docs.djangoproject.com/en/dev/releases/1.9/#foreignkey-and-onetoonefield-on-delete-argument

TODO:

• Add some more tests
• Address adding the models import if it doesn't exist
• Support detecting the on_delete call when passed as the second position argument
• Fix on_delete matcher which doesn't seem to be finding things right
• Test internally with a complicated codebase 💃

Stretch:

• Add an input so folks can add in subclasses (Edit: Probably going to do this in a future PR)

Refs #23

[browniebroke]

Thanks for the PR, this will be a very nice one to add.

The test failed because I didn't setup codecov correctly, apparently GitHub secrets aren't available to forks, which now that I think about it, makes sense. I've fixed it in #118, you might want to update your fork to get this change.

Let me know if you have any questions.

Thanks again!

[cvanderkolk]

@browniebroke thanks a bunch for taking a look at that test—I merged in those changes and things are working as expected again! 👍 This is looking pretty good! I've added some unit tests and put it thru its paces with some projects I have running locally.

I have an instance where I'd like to use this for a field that subclasses OneToOneField, do you think it's worth adding functionality via CLI to define a path to a subclass field so we can handle those too?

[browniebroke]

Looks really good! Thank you for this awesome contribution.

Looking at the test, it looks like you're testing mostly for fixing migration files. Can we add a couple for fixing model definitions as well? For example:

class MyModel(models.Model):
	user = models.ForeignKey('auth.User')

I'll look at your question and see if I have a better suggestion

[browniebroke]

These are 2 minor nitpicking that Black doesn't handle properly yet.

[sourcery-ai]

Sourcery Code Quality Report (beta)

✅ Merging this PR will increase code quality in the affected files by 0.08 out of 10.

	Before	After	Change
Quality	8.96	9.05	0.08
Complexity	1.13	1.0	-0.13
Method Length	38.84	35.59	-3.25
Lines	471	698	227

Changed files	Quality Before	Quality After	Quality Change
django_codemod/visitors/init.py	8.57	8.53	-0.04 ⬇️
django_codemod/visitors/models.py	8.2	8.42	0.22 ⬆️
tests/test_cli.py	9.22	9.21	-0.01 ⬇️
tests/visitors/test_models.py	9.4	9.5	0.1 ⬆️

Here are some functions in these files that still need a tune-up:

File	Function	Quality	Recommendation
django_codemod/visitors/models.py	ModelsPermalinkTransformer.leave_ImportFrom	4.45	Split out functionality

Please see our documentation here for details on how these metrics are calculated.

We are actively working on this report - lots more documentation and extra metrics to come!

Let us know what you think of it via email or our Gitter!

[cvanderkolk]

@browniebroke thanks for the feedback! I just submitted some changes based on your suggestions.

[browniebroke]

Thanks for this awesome contribution! This is a big one, wish I had it back when I upgraded 😄

[browniebroke]

@all-contributors please add @cvanderkolk for code

[allcontributors]

@browniebroke

I've put up a pull request to add @cvanderkolk! 🎉