Post migrate signal old content type model

[Jasper Maes]

Since the post migrate signal has the apps argument and the update_contenttypes and create_permissions listeners use this apps argument to detect the ContentType model, there can be a bug when unapplying a migration and then applying it again. The listeners will use an old model with ContentType.name still present because this in the apps of the state that the migration executor returned.

I made a ​testproject were the error is replicated.
The tests for the first app will fail, but not for the second app. I tracked this down to the migration executor were in the crashing app the migrations are in front of the migration that removes the ContentType.name field in the full_plan variable, so the executor returns a state not including this ContentType model change.

If someone can push me in the right direction I am willing to make a patch for this issue.

[Simon Charette]

I'll have a look and try to point you in the right direction, thanks for your report.

[Simon Charette]

It ended up being faster to write a fix by myself thanks to your test project, see ​PR.

Could you confirm it solves your reported issue?

[Jasper Maes]

It indeed does fix the issue. Thanks for the quick fix.

[Simon Charette]

Added tests.

[Simon Charette <charette.s@…>]

In 36d3681:

Fixed #26647 -- Included the state of all applied migrations when migrating forward.

Thanks Jasper Maes for the detailed report.

[Simon Charette <charette.s@…>]

In dfae72f:

[1.10.x] Fixed #26647 -- Included the state of all applied migrations when migrating forward.

Thanks Jasper Maes for the detailed report.

Backport of 36d36818a30025034cad6f1ee59b2a960a6582ec from master