#24434: Django Custom Field inherits ForeignKey deconstruct() fails
-------------------------------------+-------------------------------------
Reporter: greenbender | Owner: Akshat
| verma
Type: Bug | Status: assigned
Component: Documentation | Version: 1.7
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
deconstruct,migration |
Has patch: 1 | Needs documentation: 1
Needs tests: 1 | Patch needs improvement: 1
Easy pickings: 1 | UI/UX: 1
-------------------------------------+-------------------------------------
Old description:
> When creating a custom field that inherits from ForeignKey and sets the
> to field there are issues with deconstruction.
>
> Simplified example (models.py)
>
> {{{
> from django.db import models
> from django.contrib.auth.models import User
>
> class UserField(models.ForeignKey):
>
> def __init__(self, *args, **kwargs):
> kwargs['to'] = User
> super(UserField, self).__init__(*args, **kwargs)
>
> def deconstruct(self):
> name, path, args, kwargs = super(UserField, self).deconstruct()
> del kwargs['to']
> return name, path, args, kwargs
>
> class FooBar(models.Model):
> user = UserField()
> }}}
>
> When {{{python manage.py makemigrations}}} is run the following exception
> is raised.
>
> {{{
> Traceback (most recent call last):
> File "manage.py", line 10, in <module>
> execute_from_command_line(sys.argv)
> File "/usr/local/lib/python2.7/dist-
> packages/django/core/management/__init__.py", line 385, in
> execute_from_command_line
> utility.execute()
> File "/usr/local/lib/python2.7/dist-
> packages/django/core/management/__init__.py", line 377, in execute
> self.fetch_command(subcommand).run_from_argv(self.argv)
> File "/usr/local/lib/python2.7/dist-
> packages/django/core/management/base.py", line 288, in run_from_argv
> self.execute(*args, **options.__dict__)
> File "/usr/local/lib/python2.7/dist-
> packages/django/core/management/base.py", line 338, in execute
> output = self.handle(*args, **options)
> File "/usr/local/lib/python2.7/dist-
> packages/django/core/management/commands/makemigrations.py", line 111, in
> handle
> convert_apps=app_labels or None,
> File "/usr/local/lib/python2.7/dist-
> packages/django/db/migrations/autodetector.py", line 40, in changes
> changes = self._detect_changes(convert_apps, graph)
> File "/usr/local/lib/python2.7/dist-
> packages/django/db/migrations/autodetector.py", line 139, in
> _detect_changes
> self.generate_renamed_models()
> File "/usr/local/lib/python2.7/dist-
> packages/django/db/migrations/autodetector.py", line 413, in
> generate_renamed_models
> model_fields_def =
> self.only_relation_agnostic_fields(model_state.fields)
> File "/usr/local/lib/python2.7/dist-
> packages/django/db/migrations/autodetector.py", line 79, in
> only_relation_agnostic_fields
> del deconstruction[2]['to']
> KeyError: u'to'
> }}}
>
> It can be resolved by not removing the 'to' kwarg during deconstruction,
> however, this obviously leaves the unrequired 'to' kwarg in the
> constructor, as follows:
>
> {{{
> from django.db import models, migrations
> from django.conf import settings
> import bar.models
>
> class Migration(migrations.Migration):
>
> dependencies = [
> migrations.swappable_dependency(settings.AUTH_USER_MODEL),
> ]
>
> operations = [
> migrations.CreateModel(
> name='FooBar',
> fields=[
> ('id', models.AutoField(verbose_name='ID',
> serialize=False, auto_created=True, primary_key=True)),
> ('user',
> bar.models.UserField(to=settings.AUTH_USER_MODEL)),
> ],
> options={
> },
> bases=(models.Model,),
> ),
> ]
> }}}
>
> I've tried a few variations on this (such as supplying User as the first
> arg to the super call), however, the result is much the same or creates
> additional problems.
>
> The solution proposed at ticket:22263 may solve this problem.
>
>
> #When creating a custom field that inherits from ForeignKey and sets the
> to field there are issues with deconstruction.
>
> Simplified example (models.py)
> from django.db import models
> from django.contrib.auth.models import User
>
> class UserField(models.ForeignKey):
>
> def __init__(self, *args, **kwargs):
> kwargs['to'] = User
> super(UserField, self).__init__(*args, **kwargs)
>
> def deconstruct(self):
> name, path, args, kwargs = super(UserField, self).deconstruct()
> del kwargs['to']
> return name, path, args, kwargs
>
> class FooBar(models.Model):
> user = UserField()
>
> #When python manage.py makemigrations the following exception is raised.
>
> Traceback (most recent call last):
> File "manage.py", line 10, in <module>
> execute_from_command_line(sys.argv)
> File "/usr/local/lib/python2.7/dist-
> packages/django/core/management/__init__.py", line 385, in
> execute_from_command_line
> utility.execute()
> File "/usr/local/lib/python2.7/dist-
> packages/django/core/management/__init__.py", line 377, in execute
> self.fetch_command(subcommand).run_from_argv(self.argv)
> File "/usr/local/lib/python2.7/dist-
> packages/django/core/management/base.py", line 288, in run_from_argv
> self.execute(*args, **options.__dict__)
> File "/usr/local/lib/python2.7/dist-
> packages/django/core/management/base.py", line 338, in execute
> output = self.handle(*args, **options)
> File "/usr/local/lib/python2.7/dist-
> packages/django/core/management/commands/makemigrations.py", line 111, in
> handle
> convert_apps=app_labels or None,
> File "/usr/local/lib/python2.7/dist-
> packages/django/db/migrations/autodetector.py", line 40, in changes
> changes = self._detect_changes(convert_apps, graph)
> File "/usr/local/lib/python2.7/dist-
> packages/django/db/migrations/autodetector.py", line 139, in
> _detect_changes
> self.generate_renamed_models()
> File "/usr/local/lib/python2.7/dist-
> packages/django/db/migrations/autodetector.py", line 413, in
> generate_renamed_models
> model_fields_def =
> self.only_relation_agnostic_fields(model_state.fields)
> File "/usr/local/lib/python2.7/dist-
> packages/django/db/migrations/autodetector.py", line 79, in
> only_relation_agnostic_fields
> del deconstruction[2]['to']
> KeyError: u'to'
>
> #It can be resolved by not removing the 'to' kwarg during deconstruction,
> however, this obviously leaves the unrequired 'to' kwarg #in the
> constructor, as follows:
>
> from django.db import models, migrations
> from django.conf import settings
> import bar.models
>
> class Migration(migrations.Migration):
>
> dependencies = [
> migrations.swappable_dependency(settings.AUTH_USER_MODEL),
> ]
>
> operations = [
> migrations.CreateModel(
> name='FooBar',
> fields=[
> ('id', models.AutoField(verbose_name='ID',
> serialize=False, auto_created=True, primary_key=True)),
> ('user',
> bar.models.UserField(to=settings.AUTH_USER_MODEL)),
> ],
> options={
> },
> bases=(models.Model,),
> ),
> ]
New description:
When creating a custom field that inherits from ForeignKey and sets the to
field there are issues with deconstruction.
Simplified example (models.py)
{{{
from django.db import models
from django.contrib.auth.models import User
class UserField(models.ForeignKey):
def __init__(self, *args, **kwargs):
kwargs['to'] = User
super(UserField, self).__init__(*args, **kwargs)
def deconstruct(self):
name, path, args, kwargs = super(UserField, self).deconstruct()
del kwargs['to']
return name, path, args, kwargs
class FooBar(models.Model):
user = UserField()
}}}
When {{{python manage.py makemigrations}}} is run the following exception
is raised.
{{{
Traceback (most recent call last):
File "manage.py", line 10, in <module>
execute_from_command_line(sys.argv)
File "/usr/local/lib/python2.7/dist-
packages/django/core/management/__init__.py", line 385, in
execute_from_command_line
utility.execute()
File "/usr/local/lib/python2.7/dist-
packages/django/core/management/__init__.py", line 377, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "/usr/local/lib/python2.7/dist-
packages/django/core/management/base.py", line 288, in run_from_argv
self.execute(*args, **options.__dict__)
File "/usr/local/lib/python2.7/dist-
packages/django/core/management/base.py", line 338, in execute
output = self.handle(*args, **options)
File "/usr/local/lib/python2.7/dist-
packages/django/core/management/commands/makemigrations.py", line 111, in
handle
convert_apps=app_labels or None,
File "/usr/local/lib/python2.7/dist-
packages/django/db/migrations/autodetector.py", line 40, in changes
changes = self._detect_changes(convert_apps, graph)
File "/usr/local/lib/python2.7/dist-
packages/django/db/migrations/autodetector.py", line 139, in
_detect_changes
self.generate_renamed_models()
File "/usr/local/lib/python2.7/dist-
packages/django/db/migrations/autodetector.py", line 413, in
generate_renamed_models
model_fields_def =
self.only_relation_agnostic_fields(model_state.fields)
File "/usr/local/lib/python2.7/dist-
packages/django/db/migrations/autodetector.py", line 79, in
only_relation_agnostic_fields
del deconstruction[2]['to']
KeyError: u'to'
}}}
--
Comment (by Mariusz Felisiak):
Akshat, please stop or I'll block your from Django org. Your comments are
disturbing and random. You could also check formatting issues before
posting. I'm going to delete all your future comments, if they will be as
useless as they are now.
--
Ticket URL: <https://code.djangoproject.com/ticket/24434#comment:8>
Django <https://code.djangoproject.com/>
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