Re: [Django] #18510: Options._fill_related_objects_cache should assert for app_cache_ready() or deal with app_cache_ready() == False

[Django]

#18510: Options._fill_related_objects_cache should assert for app_cache_ready() 
or
deal with app_cache_ready() == False
-+-
 Reporter:  vanschelven  |Owner:  nobody
 Type:  Bug  |   Status:  closed
Component:  Database layer   |  Version:  1.4
  (models, ORM)  |   Resolution:  fixed
 Severity:  Normal   | Triage Stage:  Accepted
 Keywords:  app-loading  |  Needs documentation:  0
Has patch:  1|  Patch needs improvement:  0
  Needs tests:  0|UI/UX:  0
Easy pickings:  0|
-+-
Changes (by aaugustin):

 * keywords:   => app-loading
 * status:  new => closed
 * resolution:   => fixed


Comment:

 This is "fixed" by the app-loading refactor, in the sense that Django now
 throws an explicit exception.

 '''stable/1.6.x -- obscure test failure'''

 {{{
 Creating test database for alias 'default'...
 E
 ==
 ERROR: test_get_field_by_name (testapp.tests.SimpleTest)
 --
 Traceback (most recent call last):
   File "~/django/django/db/models/options.py", line 371, in
 get_field_by_name
 return self._name_map[name]
 KeyError: 'userprofile'

 During handling of the above exception, another exception occurred:

 Traceback (most recent call last):
   File "~/django/t18510/testapp/tests.py", line 10, in
 test_get_field_by_name
 User._meta.get_field_by_name('userprofile')
   File "~/django/django/db/models/options.py", line 377, in
 get_field_by_name
 % (self.object_name, name))
 django.db.models.fields.FieldDoesNotExist: User has no field named
 'userprofile'

 --
 Ran 1 test in 0.002s

 FAILED (errors=1)
 Destroying test database for alias 'default'...
 }}}

 '''stable/1.7.x -- explicit exception'''

 {{{
 Traceback (most recent call last):
   File "~/django/django/db/models/options.py", line 414, in
 get_field_by_name
 return self._name_map[name]
 AttributeError: 'Options' object has no attribute '_name_map'

 During handling of the above exception, another exception occurred:

 Traceback (most recent call last):
   File "~/django/django/db/models/options.py", line 559, in
 get_all_related_m2m_objects_with_model
 cache = self._related_many_to_many_cache
 AttributeError: 'Options' object has no attribute
 '_related_many_to_many_cache'

 During handling of the above exception, another exception occurred:

 Traceback (most recent call last):
   File "./manage.py", line 10, in 
 execute_from_command_line(sys.argv)
   File "~/django/django/core/management/__init__.py", line 385, in
 execute_from_command_line
 utility.execute()
   File "~/django/django/core/management/__init__.py", line 354, in execute
 django.setup()
   File "~/django/django/__init__.py", line 21, in setup
 apps.populate(settings.INSTALLED_APPS)
   File "~/django/django/apps/registry.py", line 106, in populate
 app_config.import_models(all_models)
   File "~/django/django/apps/config.py", line 190, in import_models
 self.models_module = import_module(models_module_name)
   File "~/.virtualenvs/django/lib/python3.4/importlib/__init__.py", line
 104, in import_module
 return _bootstrap._gcd_import(name[level:], package, level)
   File "", line 2231, in _gcd_import
   File "", line 2214, in _find_and_load
   File "", line 2203, in
 _find_and_load_unlocked
   File "", line 1200, in _load_unlocked
   File "", line 1129, in _exec
   File "", line 1448, in exec_module
   File "", line 321, in
 _call_with_frames_removed
   File "~/django/t18510/testapp/models.py", line 5, in 
 User._meta.get_field_by_name('username')
   File "~/django/django/db/models/options.py", line 416, in
 get_field_by_name
 cache = self.init_name_map()
   File "~/django/django/db/models/options.py", line 445, in init_name_map
 for f, model in self.get_all_related_m2m_objects_with_model():
   File "~/django/django/db/models/options.py", line 561, in
 get_all_related_m2m_objects_with_model
 cache = self._fill_related_many_to_many_cache()
   File "~/django/django/db/models/options.py", line 575, in
 _fill_related_many_to_many_cache
 for klass in self.apps.get_models():
   File "~/.virtualenvs/django/lib/python3.4/functools.py", line 428, in
 wrapper
 result = user_function(*args, **kwds)
   File "~/django/django/apps/registry.py", line 156, in get_models
 self.check_ready()
   File "~/django/django/apps/registry.py", line 119, in check_ready
 raise RuntimeError("App registry isn't ready yet.")
 RuntimeError: App registry isn't 

Re: [Django] #18510: Options._fill_related_objects_cache should assert for app_cache_ready() or deal with app_cache_ready() == False

[Django]

#18510: Options._fill_related_objects_cache should assert for app_cache_ready() 
or
deal with app_cache_ready() == False
-+-
 Reporter:  vanschelven  |Owner:  nobody
 Type:  Bug  |   Status:  new
Component:  Database layer   |  Version:  1.4
  (models, ORM)  |   Resolution:
 Severity:  Normal   | Triage Stage:  Accepted
 Keywords:   |  Needs documentation:  0
Has patch:  1|  Patch needs improvement:  0
  Needs tests:  0|UI/UX:  0
Easy pickings:  0|
-+-
Changes (by aaugustin):

 * type:  Uncategorized => Bug
 * stage:  Unreviewed => Accepted


-- 
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Re: [Django] #18510: Options._fill_related_objects_cache should assert for app_cache_ready() or deal with app_cache_ready() == False

[Django]

#18510: Options._fill_related_objects_cache should assert for app_cache_ready() 
or
deal with app_cache_ready() == False
-+-
 Reporter:  vanschelven  |Owner:  nobody
 Type:  Uncategorized|   Status:  new
Component:  Database layer   |  Version:  1.4
  (models, ORM)  |   Resolution:
 Severity:  Normal   | Triage Stage:
 Keywords:   |  Unreviewed
Has patch:  1|  Needs documentation:  0
  Needs tests:  0|  Patch needs improvement:  0
Easy pickings:  0|UI/UX:  0
-+-
Changes (by vanschelven):

 * cc: vanschelven (added)
 * needs_better_patch:   => 0
 * has_patch:  0 => 1
 * needs_tests:   => 0
 * needs_docs:   => 0


-- 
Ticket URL: 
Django 
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[Django] #18510: Options._fill_related_objects_cache should assert for app_cache_ready() or deal with app_cache_ready() == False

[Django]

#18510: Options._fill_related_objects_cache should assert for app_cache_ready() 
or
deal with app_cache_ready() == False
--+
 Reporter:  vanschelven   |  Owner:  nobody
 Type:  Uncategorized | Status:  new
Component:  Database layer (models, ORM)  |Version:  1.4
 Severity:  Normal|   Keywords:
 Triage Stage:  Unreviewed|  Has patch:  0
Easy pickings:  0 |  UI/UX:  0
--+
 It is possible to end up in Options._fill_related_many_to_many_cache
 (https://github.com/django/django/blob/1.4/django/db/models/options.py#L388)
 while app_cache_ready() is False. Since that method iterates over
 get_models() (line 401) and saves its result in an object attribute
 regardless of the value of app_cache_ready() in line 409 this may result
 in the _related_objects_cache missing elements, causing get_field_by_name
 (and possibly other methods) to fail.

 Steps to reproduce:

 {{{
 # models.py
 from django.db import models

 from django.contrib.auth.models import User
 User._meta.get_field_by_name('username')

 # alternatively, import the below to trigger the error.
 # from django.contrib.auth.admin import UserAdmin

 class UserProfile(models.Model):
 user = models.ForeignKey(User, unique=True, editable=False)
 first_name = models.CharField(max_length=255, blank=True)

 User._meta.ordering = ('userprofile__first_name',)
 }}}

 {{{
 # tests.py
 from django.test import TestCase

 from django.contrib.auth.models import User

 class SimpleTest(TestCase):
 def test_get_field_by_name(self):
 # no assertions needed, the test simply fails
 User.objects.create(username='test')
 User._meta.get_field_by_name('userprofile')

 # similarly methods using get_field_by_name themselves fail, such
 as
 u = User.objects.all()[0]
 }}}


 {{{
 --
 Traceback (most recent call last):
   File "/tmp/ve13/reverselookup/userprofile/tests.py", line 9, in
 test_get_field_by_name
 User._meta.get_field_by_name('userprofile')
   File "/tmp/ve14/lib/python2.6/site-
 packages/django/db/models/options.py", line 315, in get_field_by_name
 % (self.object_name, name))
 !FieldDoesNotExist: User has no field named 'userprofile'
 }}}

 This fails in both Django 1.3 and Django 1.4.

 Solution:
 The canonical solution in options.py seems to be to check for the value of
 app_cache_ready() before actually setting the internal cache attribute.
 E.g.
 https://github.com/django/django/blob/1.4/django/db/models/options.py#L447
 . I'm not sure whether that would fix all problems caused by this or
 whether an assert for app_cache_ready() at the top of the method would be
 more appropriate.

 I'm currently not able to come up with a proper way of providing tests for
 the situation above, because the global state of app loading and such
 makes coming up with tests somewhat harder. If anyone can help me with
 that, that would be great. Alternatively perhaps someone is willing to
 take the above method of reproduction and the fact that no old tests break
 as enough reason for a patch?

 Admittedly the above scenario appears contrived (calling
 User._meta.get_field_by_name('username') in a models.py file). However,
 this is simply the easiest way to reproduce the problem.

 I ran into this when further debugging #18507 . In that case I was using
 from django.contrib.auth.admin import !UserAdmin somewhere early in one of
 my models files. Since Django 1.3 adds more validation to the admins, one
 of which contained a call to get_field_by_name this resulted in a rather
 hard-to-debug problem when upgrading from Django 1.2 to Django 1.3 (or
 1.4).

-- 
Ticket URL: 
Django 
The Web framework for perfectionists with deadlines.

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