[1.5.x] Fix #19524 -- Incorrect caching of parents of unsaved model instances.

Thanks qcwxezdas for the report. Refs #13839.

Backport of e9c24be.

5 files changed, 48 insertions, 4 deletions

diff --git a/django/db/models/base.py b/django/db/models/base.py
index bf9854d289..bd638e2499 100644
--- a/django/db/models/base.py
+++ b/django/db/models/base.py
@@ -583,6 +583,15 @@ class Model(six.with_metaclass(ModelBase, object)):
 
                 if field:
                     setattr(self, field.attname, self._get_pk_val(parent._meta))
+                    # Since we didn't have an instance of the parent handy, we
+                    # set attname directly, bypassing the descriptor.
+                    # Invalidate the related object cache, in case it's been
+                    # accidentally populated. A fresh instance will be
+                    # re-built from the database if necessary.
+                    cache_name = field.get_cache_name()
+                    if hasattr(self, cache_name):
+                        delattr(self, cache_name)
+
             if meta.proxy:
                 return
 
diff --git a/django/forms/models.py b/django/forms/models.py
index 0913a4e8b8..27c246b668 100644
--- a/django/forms/models.py
+++ b/django/forms/models.py
@@ -692,7 +692,10 @@ class BaseInlineFormSet(BaseModelFormSet):
         self.rel_name = RelatedObject(self.fk.rel.to, self.model, self.fk).get_accessor_name()
         if queryset is None:
             queryset = self.model._default_manager
-        qs = queryset.filter(**{self.fk.name: self.instance})
+        if self.instance.pk:
+            qs = queryset.filter(**{self.fk.name: self.instance})
+        else:
+            qs = queryset.none()
         super(BaseInlineFormSet, self).__init__(data, files, prefix=prefix,
                                                 queryset=qs, **kwargs)
 
diff --git a/tests/regressiontests/admin_inlines/admin.py b/tests/regressiontests/admin_inlines/admin.py
index cf51fa49b4..536c3ec079 100644
--- a/tests/regressiontests/admin_inlines/admin.py
+++ b/tests/regressiontests/admin_inlines/admin.py
@@ -124,6 +124,9 @@ class ChildModel1Inline(admin.TabularInline):
 class ChildModel2Inline(admin.StackedInline):
     model = ChildModel2
 
+# admin for #19524
+class SightingInline(admin.TabularInline):
+    model = Sighting
 
 site.register(TitleCollection, inlines=[TitleInline])
 # Test bug #12561 and #12778
@@ -141,4 +144,5 @@ site.register(Holder4, Holder4Admin)
 site.register(Author, AuthorAdmin)
 site.register(CapoFamiglia, inlines=[ConsigliereInline, SottoCapoInline])
 site.register(ProfileCollection, inlines=[ProfileInline])
-site.register(ParentModelWithCustomPk, inlines=[ChildModel1Inline, ChildModel2Inline])
\ No newline at end of file
+site.register(ParentModelWithCustomPk, inlines=[ChildModel1Inline, ChildModel2Inline])
+site.register(ExtraTerrestrial, inlines=[SightingInline])
diff --git a/tests/regressiontests/admin_inlines/models.py b/tests/regressiontests/admin_inlines/models.py
index b004d5f85a..147873a9e8 100644
--- a/tests/regressiontests/admin_inlines/models.py
+++ b/tests/regressiontests/admin_inlines/models.py
@@ -90,7 +90,6 @@ class Inner4Tabular(models.Model):
     dummy = models.IntegerField(help_text="Awesome tabular help text is awesome.")
     holder = models.ForeignKey(Holder4)
 
-
 # Models for #12749
 
 class Person(models.Model):
@@ -133,6 +132,7 @@ class Chapter(models.Model):
 
 
 # Models for #16838
+
 class CapoFamiglia(models.Model):
     name = models.CharField(max_length=100)
 
@@ -170,6 +170,17 @@ class ChildModel2(models.Model):
     def get_absolute_url(self):
         return '/child_model2/'
 
+# Models for #19524
+
+class LifeForm(models.Model):
+    pass
+
+class ExtraTerrestrial(LifeForm):
+    name = models.CharField(max_length=100)
+
+class Sighting(models.Model):
+    et = models.ForeignKey(ExtraTerrestrial)
+    place = models.CharField(max_length=100)
 
 # Other models
 
diff --git a/tests/regressiontests/admin_inlines/tests.py b/tests/regressiontests/admin_inlines/tests.py
index 3c868012fa..54283bf509 100644
--- a/tests/regressiontests/admin_inlines/tests.py
+++ b/tests/regressiontests/admin_inlines/tests.py
@@ -12,7 +12,7 @@ from .admin import InnerInline, TitleInline, site
 from .models import (Holder, Inner, Holder2, Inner2, Holder3, Inner3, Person,
     OutfitItem, Fashionista, Teacher, Parent, Child, Author, Book, Profile,
     ProfileCollection, ParentModelWithCustomPk, ChildModel1, ChildModel2,
-    Title)
+    Sighting, Title)
 
 
 @override_settings(PASSWORD_HASHERS=('django.contrib.auth.hashers.SHA1PasswordHasher',))
@@ -172,6 +172,23 @@ class TestInline(TestCase):
         self.assertContains(response, child1_shortcut)
         self.assertContains(response, child2_shortcut)
 
+    def test_create_inlines_on_inherited_model(self):
+        """
+        Ensure that an object can be created with inlines when it inherits
+        another class. Bug #19524.
+        """
+        data = {
+            'name': 'Martian',
+            'sighting_set-TOTAL_FORMS': 1,
+            'sighting_set-INITIAL_FORMS': 0,
+            'sighting_set-MAX_NUM_FORMS': 0,
+            'sighting_set-0-place': 'Zone 51',
+            '_save': 'Save',
+        }
+        response = self.client.post('/admin/admin_inlines/extraterrestrial/add/', data)
+        self.assertEqual(response.status_code, 302)
+        self.assertEqual(Sighting.objects.filter(et__name='Martian').count(), 1)
+
 
 @override_settings(PASSWORD_HASHERS=('django.contrib.auth.hashers.SHA1PasswordHasher',))
 class TestInlineMedia(TestCase):