#22875: "ValueError: Lookup failed for model referenced by field
app.Model.m2mfield: app.ThroghModel" in simple-self contained M2M setup
--------------------------------------+----------------------------
Reporter: ramiro | Owner: nobody
Type: Bug | Status: new
Component: Migrations | Version: 1.7-beta-2
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 |
--------------------------------------+----------------------------
In a simple `ManyToManyField` with intermediate model setup involving
three models in the same application:
{{{
# app_b/models.py
from django.db import models
class Employee(models.Model):
name = models.CharField(max_length=30)
class Employer(models.Model):
name = models.CharField(max_length=30)
employees = models.ManyToManyField(Employee, through='Employment')
class Employment(models.Model):
employee = models.ForeignKey(Employee)
employer = models.ForeignKey(Employer)
recruiting_date = models.DateField()
}}}
I'm seeing the following traceback when running `migrate` after the
initial migration has been created for the app:
{{{
~/dtest/dtest002$ rm -rf db.sqlite3 app_b/migrations
~/dtest/dtest002$ PYTHONPATH=~/django/upstream python ./manage.py
makemigrations
No changes detected
ramiro@serverid:~/dtest/dtest002$ PYTHONPATH=~/django/upstream python
./manage.py makemigrations app_b
Migrations for 'app_b':
0001_initial.py:
- Create model Employee
- Create model Employer
- Create model Employment
~/dtest/dtest002$ PYTHONPATH=~/django/upstream python ./manage.py migrate
Operations to perform:
Synchronize unmigrated apps: (none)
Apply all migrations: admin, contenttypes, app_b, auth, sessions
Synchronizing apps without migrations:
Creating tables...
Installing custom SQL...
Installing indexes...
Running migrations:
Applying contenttypes.0001_initial... OK
Applying auth.0001_initial... OK
Applying admin.0001_initial... OK
Applying app_b.0001_initial...Traceback (most recent call last):
File "./manage.py", line 10, in <module>
execute_from_command_line(sys.argv)
File "/home/xxx/django/upstream/django/core/management/__init__.py",
line 385, in execute_from_command_line
utility.execute()
File "/home/xxx/django/upstream/django/core/management/__init__.py",
line 377, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "/home/xxx/django/upstream/django/core/management/base.py", line
288, in run_from_argv
self.execute(*args, **options.__dict__)
File "/home/xxx/django/upstream/django/core/management/base.py", line
337, in execute
output = self.handle(*args, **options)
File
"/home/xxx/django/upstream/django/core/management/commands/migrate.py",
line 146, in handle
executor.migrate(targets, plan, fake=options.get("fake", False))
File "/home/xxx/django/upstream/django/db/migrations/executor.py", line
62, in migrate
self.apply_migration(migration, fake=fake)
File "/home/xxx/django/upstream/django/db/migrations/executor.py", line
96, in apply_migration
migration.apply(project_state, schema_editor)
File "/home/xxx/django/upstream/django/db/migrations/migration.py", line
107, in apply
operation.database_forwards(self.app_label, schema_editor,
project_state, new_state)
File
"/home/xxx/django/upstream/django/db/migrations/operations/models.py",
line 33, in database_forwards
apps = to_state.render()
File "/home/xxx/django/upstream/django/db/migrations/state.py", line 89,
in render
model=lookup_model,
ValueError: Lookup failed for model referenced by field
app_b.Employer.employees: app_b.Employment
}}}
I'm selecting '1.7/beta-2' as Version but I'm running the latest
`stable/1.7.x` code:
{{{
~/django/upstream$ git log -1
commit 30d8b95139a1fa3070f3b112115e624ffcf8e555
Author: Tim Graham <[email protected]>
Date: Thu Jun 19 11:02:53 2014 -0400
[1.7.x] Added feature for implied null (needed for Firebird backend)
Backport of 1b07781292 from master
}}}
Initially Employee didn't exist and the m2m relationship was against a
custom User model.
After that trying to create a minimal setup that reproduces the issue,
usage of the swappable user model feature was removed and the m2m field
was re-pointed to standard auth.User, and finally to a local Employee
model.
--
Ticket URL: <https://code.djangoproject.com/ticket/22875>
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