If the only manager on the model is the default manager defined
by Django (`objects = models.Manager()`), this manager will not
be added to the model state. If it is custom, it needs to be
passed to the model state.
This also prevents state modifications from corrupting previous states.
Previously, when a model defining a relation was unregistered first,
clearing the cache would cause its related models' _meta to be cleared
and would result in the old models losing track of their relations.
Calling Migration.mutate_state() now also allows to do in_place
mutations in case an intermediate state is thrown away later.
Thanks Anssi Kääriäinen for the idea, Ryan Hall for parts of the patch,
and Claude Paroz and Tim Graham for the review
This adds a new method, Apps.lazy_model_operation(), and a helper function,
lazy_related_operation(), which together supersede add_lazy_relation() and
make lazy model operations the responsibility of the App registry. This
system no longer uses the class_prepared signal.
Field.rel is now deprecated. Rel objects have now also remote_field
attribute. This means that self == self.remote_field.remote_field.
In addition, made the Rel objects a bit more like Field objects. Still,
marked ManyToManyFields as null=True.
Set apps.ready to False when rendering multiple models. This prevents
that the cache on Model._meta is expired on all models after each time a
single model is rendered. Prevented that Apps.clear_cache() refills the
cache on Apps.get_models(), so that the wrong value cannot be cached
when cloning a StateApps.
Swapped out models don't have a _default_manager unless they have
explicitly defined managers. ModelState.from_model() now accounts for
this case and uses an empty list for managers if no explicit managers
are defined and a model is swapped out.
Instead of naively reloading only directly related models (FK, O2O, M2M
relationship) the project state needs to reload their relations as well
as the model changes as well. Furthermore inheriting models (and super
models) need to be reloaded in order to keep inherited fields in sync.
To prevent endless recursive calls an iterative approach is taken.
Made sure the app labels stay unique for the AppConfigStubs, so
migrations wouldn't fail if two dotted app names has the same last part
(e.g. django.contrib.auth and vendor.auth)
In some cases, this could lead to migrations written with Python 2
being incompatible with Python 3.
Thanks Tim Graham for the report and Loïc Bistuer for the advices.
Tim Graham
Simon Charette
Alex Hill
Kai Richard Koenig
Andriy Sokolovskiy
Markus Holtermann
Luis Del Giudice
Marten Kenbeek
Patryk Zawadzki
Anssi Kääriäinen
Ulrich Petri
Daniel Pyrathon
Claude Paroz
Jon Dufresne
Berker Peksag
Carl Meyer
Szilveszter Farkas
Andrew Godwin
Loic Bistuer
Aymeric Augustin