From 1d485cf14ffa58dbeb130db2d50aa147556e0244 Mon Sep 17 00:00:00 2001
From: Jannis Leidel <jannis@leidel.info>
Date: Fri, 12 Aug 2011 14:15:08 +0000
Subject: [PATCH] Fixed #10405 -- Raise a more useful error if the formfield of
 a related model field can't be created yet because the related model isn't
 loaded yet. Thanks ojii and charstring.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@16604 bcc190cf-cafb-0310-a4f2-bffc1f526a37
---
 django/core/exceptions.py                   |  2 +-
 django/db/models/fields/related.py          |  4 +++
 tests/regressiontests/forms/tests/models.py | 33 +++++++++++++++++++++
 3 files changed, 38 insertions(+), 1 deletion(-)

diff --git a/django/core/exceptions.py b/django/core/exceptions.py
index 21be8702fa..201a854a4b 100644
--- a/django/core/exceptions.py
+++ b/django/core/exceptions.py
@@ -3,7 +3,7 @@ Global Django exception and warning classes.
 """
 
 class DjangoRuntimeWarning(RuntimeWarning):
-   pass
+    pass
 
 class ObjectDoesNotExist(Exception):
     "The requested object does not exist"
diff --git a/django/db/models/fields/related.py b/django/db/models/fields/related.py
index e7f4b9b3de..3e861cddd2 100644
--- a/django/db/models/fields/related.py
+++ b/django/db/models/fields/related.py
@@ -905,6 +905,10 @@ class ForeignKey(RelatedField, Field):
 
     def formfield(self, **kwargs):
         db = kwargs.pop('using', None)
+        if isinstance(self.rel.to, basestring):
+            raise ValueError("Cannot create form field for %r yet, because "
+                             "its related model %r has not been loaded yet" %
+                             (self.name, self.rel.to))
         defaults = {
             'form_class': forms.ModelChoiceField,
             'queryset': self.rel.to._default_manager.using(db).complex_filter(self.rel.limit_choices_to),
diff --git a/tests/regressiontests/forms/tests/models.py b/tests/regressiontests/forms/tests/models.py
index 5e1bd82640..60fc4e83ba 100644
--- a/tests/regressiontests/forms/tests/models.py
+++ b/tests/regressiontests/forms/tests/models.py
@@ -1,7 +1,9 @@
 # -*- coding: utf-8 -*-
 import datetime
 from django.core.files.uploadedfile import SimpleUploadedFile
+from django.db import models
 from django.forms import Form, ModelForm, FileField, ModelChoiceField
+from django.forms.models import ModelFormMetaclass
 from django.test import TestCase
 from regressiontests.forms.models import (ChoiceOptionModel, ChoiceFieldModel,
     FileModel, Group, BoundaryModel, Defaults)
@@ -160,3 +162,34 @@ class FormsModelTestCase(TestCase):
         self.assertEqual(obj.name, u'class default value')
         self.assertEqual(obj.value, 99)
         self.assertEqual(obj.def_date, datetime.date(1999, 3, 2))
+
+class RelatedModelFormTests(TestCase):
+    def test_invalid_loading_order(self):
+        """
+        Test for issue 10405
+        """
+        class A(models.Model):
+            ref = models.ForeignKey("B")
+
+        class Meta:
+            model=A
+
+        self.assertRaises(ValueError, ModelFormMetaclass, 'Form', (ModelForm,), {'Meta': Meta})
+
+        class B(models.Model):
+            pass
+
+    def test_valid_loading_order(self):
+        """
+        Test for issue 10405
+        """
+        class A(models.Model):
+            ref = models.ForeignKey("B")
+
+        class B(models.Model):
+            pass
+
+        class Meta:
+            model=A
+
+        self.assertTrue(issubclass(ModelFormMetaclass('Form', (ModelForm,), {'Meta': Meta}), ModelForm))