Re: [Django] #25145: Models of apps w/o migrations don't have relational fields to other apps w/o migrations when applying migrations

[Django]

#25145: Models of apps w/o migrations don't have relational fields to other apps
w/o migrations when applying migrations
+--
 Reporter:  MarkusH |Owner:  nobody
 Type:  Bug |   Status:  closed
Component:  Migrations  |  Version:  1.8
 Severity:  Normal  |   Resolution:  duplicate
 Keywords:  | Triage Stage:  Unreviewed
Has patch:  0   |  Needs documentation:  0
  Needs tests:  0   |  Patch needs improvement:  0
Easy pickings:  0   |UI/UX:  0
+--
Changes (by timgraham):

 * status:  new => closed
 * resolution:   => duplicate


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Ticket URL: 
Django 
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Re: [Django] #25145: Models of apps w/o migrations don't have relational fields to other apps w/o migrations when applying migrations

[Django]

#25145: Models of apps w/o migrations don't have relational fields to other apps
w/o migrations when applying migrations
+--
 Reporter:  MarkusH |Owner:  nobody
 Type:  Bug |   Status:  new
Component:  Migrations  |  Version:  1.8
 Severity:  Normal  |   Resolution:
 Keywords:  | Triage Stage:  Unreviewed
Has patch:  0   |  Needs documentation:  0
  Needs tests:  0   |  Patch needs improvement:  0
Easy pickings:  0   |UI/UX:  0
+--

Comment (by timgraham):

 Don't you need to add a dependency to `wo_migrations1` on `w_migrations`
 if you want to use its models? In which case, you have the case of
 migrated apps depending on unmigrated apps which isn't supported.

 https://docs.djangoproject.com/en/1.8/topics/migrations/#accessing-models-
 from-other-apps

 See also #24853 and the docs added in that ticket.

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[Django] #25145: Models of apps w/o migrations don't have relational fields to other apps w/o migrations when applying migrations

[Django]

#25145: Models of apps w/o migrations don't have relational fields to other apps
w/o migrations when applying migrations
--+
   Reporter:  MarkusH |  Owner:  nobody
   Type:  Bug | Status:  new
  Component:  Migrations  |Version:  1.8
   Severity:  Normal  |   Keywords:
   Triage Stage:  Unreviewed  |  Has patch:  0
Needs documentation:  0   |Needs tests:  0
Patch needs improvement:  0   |  Easy pickings:  0
  UI/UX:  0   |
--+
 Consider the three apps `w_migrations`, `wo_migrations1` and
 `wo_migrations2` with the following models:

 `w_migrations`:

 {{{#!python
 class With(models.Model):
 without1 = models.ForeignKey('wo_migrations1.Without1')
 }}}

 `wo_migrations1`:

 {{{#!python
 class Without1(models.Model):
 without2 = models.ForeignKey('wo_migrations2.Without2')
 }}}

 `wo_migrations2`:

 {{{#!python
 class Without2(models.Model):
 i = models.IntegerField()
 }}}

 When you create the migration for `w_migrations` and add an additional
 `RunPython` operation:

 {{{#!python

 def forward(apps, schema_editor):
 print(apps.get_model('wo_migrations1',
 'Without1')._meta._get_fields())


 operations = [
 ...,
 migrations.RunPython(forward, migrations.RunPython.noop),
 ]
 }}}

 you will get the following output:

 {{{#!python
 (,)
 }}}

 However, one would expect to see the `ForeignKey` to `wo_migrations2`,
 too.

 A fix should be rather simple by updating
 `django.db.migrations.state.ModelState.from_model()` similar to those
 lines:

 {{{#!diff
 diff --git a/django/db/migrations/state.py b/django/db/migrations/state.py
 index b1cba07..4dd25ba 100644
 --- a/django/db/migrations/state.py
 +++ b/django/db/migrations/state.py
 @@ -219,7 +219,7 @@ class StateApps(Apps):
  for app_label in real_apps:
  app = global_apps.get_app_config(app_label)
  for model in app.get_models():
 -self.real_models.append(ModelState.from_model(model,
 exclude_rels=True))
 +self.real_models.append(ModelState.from_model(model,
 exclude_rels=True, allow_rels_to=real_apps))
  # Populate the app registry with a stub for each application.
  app_labels = {model_state.app_label for model_state in
 models.values()}
  app_configs = [AppConfigStub(label) for label in sorted(real_apps
 + list(app_labels))]
 @@ -346,14 +346,15 @@ class ModelState(object):
  return self.name.lower()

  @classmethod
 -def from_model(cls, model, exclude_rels=False):
 +def from_model(cls, model, exclude_rels=False, allow_rels_to=[]):
  """
  Feed me a model, get a ModelState representing it out.
  """
  # Deconstruct the fields
  fields = []
  for field in model._meta.local_fields:
 -if getattr(field, "remote_field", None) and exclude_rels:
 +if (exclude_rels and field.is_relation and
 +_get_app_label_and_model_name(field.related_model)[0]
 not in allow_rels_to):
  continue
  if isinstance(field, OrderWrt):
  continue
 @@ -367,18 +368,20 @@ class ModelState(object):
  model._meta.label,
  e,
  ))
 -if not exclude_rels:
 -for field in model._meta.local_many_to_many:
 -name, path, args, kwargs = field.deconstruct()
 -field_class = import_string(path)
 -try:
 -fields.append((name, field_class(*args, **kwargs)))
 -except TypeError as e:
 -raise TypeError("Couldn't reconstruct m2m field %s on
 %s: %s" % (
 -name,
 -model._meta.object_name,
 -e,
 -))
 +for field in model._meta.local_many_to_many:
 +if (exclude_rels and field.is_relation and
 +_get_app_label_and_model_name(field.related_model)[0]
 not in allow_rels_to):
 +continue
 +name, path, args, kwargs = field.deconstruct()
 +field_class = import_string(path)
 +try:
 +fields.append((name, field_class(*args, **kwargs)))
 +except TypeError as e:
 +raise TypeError("Couldn't reconstruct m2m field %s on %s:
 %s" % (
 +name,
 +model._meta.object_name,
 +e,
 +))
  # Extract the options
  options = {}
  for name in DEFAULT_NAMES:
 }}}

 I believe this bug is also present on 1.8, haven't investigated though. If
 it is, it is I think it is a regression from 1.7 to 1.8.

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Ticket URL: