Fixed #27272 -- Added an on_delete RESTRICT handler to allow cascading deletions while protecting direct ones.

2 files changed, 140 insertions, 5 deletions

diff --git a/tests/delete/models.py b/tests/delete/models.py
index e2ddce0588..7a38ecc777 100644
--- a/tests/delete/models.py
+++ b/tests/delete/models.py
@@ -1,8 +1,17 @@
+from django.contrib.contenttypes.fields import (
+    GenericForeignKey, GenericRelation,
+)
+from django.contrib.contenttypes.models import ContentType
 from django.db import models
 
 
+class P(models.Model):
+    pass
+
+
 class R(models.Model):
     is_default = models.BooleanField(default=False)
+    p = models.ForeignKey(P, models.CASCADE, null=True)
 
     def __str__(self):
         return "%s" % self.pk
@@ -46,10 +55,12 @@ class A(models.Model):
     )
     cascade = models.ForeignKey(R, models.CASCADE, related_name='cascade_set')
     cascade_nullable = models.ForeignKey(R, models.CASCADE, null=True, related_name='cascade_nullable_set')
-    protect = models.ForeignKey(R, models.PROTECT, null=True)
+    protect = models.ForeignKey(R, models.PROTECT, null=True, related_name='protect_set')
+    restrict = models.ForeignKey(R, models.RESTRICT, null=True, related_name='restrict_set')
     donothing = models.ForeignKey(R, models.DO_NOTHING, null=True, related_name='donothing_set')
     child = models.ForeignKey(RChild, models.CASCADE, related_name="child")
     child_setnull = models.ForeignKey(RChild, models.SET_NULL, null=True, related_name="child_setnull")
+    cascade_p = models.ForeignKey(P, models.CASCADE, related_name='cascade_p_set', null=True)
 
     # A OneToOneField is just a ForeignKey unique=True, so we don't duplicate
     # all the tests; just one smoke test to ensure on_delete works for it as
@@ -61,7 +72,7 @@ def create_a(name):
     a = A(name=name)
     for name in ('auto', 'auto_nullable', 'setvalue', 'setnull', 'setdefault',
                  'setdefault_none', 'cascade', 'cascade_nullable', 'protect',
-                 'donothing', 'o2o_setnull'):
+                 'restrict', 'donothing', 'o2o_setnull'):
         r = R.objects.create()
         setattr(a, name, r)
     a.child = RChild.objects.create()
@@ -147,3 +158,45 @@ class SecondReferrer(models.Model):
     other_referrer = models.ForeignKey(
         Referrer, models.CASCADE, to_field='unique_field', related_name='+'
     )
+
+
+class DeleteTop(models.Model):
+    b1 = GenericRelation('GenericB1')
+    b2 = GenericRelation('GenericB2')
+
+
+class B1(models.Model):
+    delete_top = models.ForeignKey(DeleteTop, models.CASCADE)
+
+
+class B2(models.Model):
+    delete_top = models.ForeignKey(DeleteTop, models.CASCADE)
+
+
+class DeleteBottom(models.Model):
+    b1 = models.ForeignKey(B1, models.RESTRICT)
+    b2 = models.ForeignKey(B2, models.CASCADE)
+
+
+class GenericB1(models.Model):
+    content_type = models.ForeignKey(ContentType, on_delete=models.CASCADE)
+    object_id = models.PositiveIntegerField()
+    generic_delete_top = GenericForeignKey('content_type', 'object_id')
+
+
+class GenericB2(models.Model):
+    content_type = models.ForeignKey(ContentType, on_delete=models.CASCADE)
+    object_id = models.PositiveIntegerField()
+    generic_delete_top = GenericForeignKey('content_type', 'object_id')
+    generic_delete_bottom = GenericRelation('GenericDeleteBottom')
+
+
+class GenericDeleteBottom(models.Model):
+    generic_b1 = models.ForeignKey(GenericB1, models.RESTRICT)
+    content_type = models.ForeignKey(ContentType, on_delete=models.CASCADE)
+    object_id = models.PositiveIntegerField()
+    generic_b2 = GenericForeignKey()
+
+
+class GenericDeleteBottomParent(models.Model):
+    generic_delete_bottom = models.ForeignKey(GenericDeleteBottom, on_delete=models.CASCADE)
diff --git a/tests/delete/tests.py b/tests/delete/tests.py
index d61fdb40c1..b93bdd5265 100644
--- a/tests/delete/tests.py
+++ b/tests/delete/tests.py
@@ -1,13 +1,14 @@
 from math import ceil
 
 from django.db import IntegrityError, connection, models
-from django.db.models.deletion import Collector
+from django.db.models.deletion import Collector, RestrictedError
 from django.db.models.sql.constants import GET_ITERATOR_CHUNK_SIZE
 from django.test import TestCase, skipIfDBFeature, skipUnlessDBFeature
 
 from .models import (
-    MR, A, Avatar, Base, Child, HiddenUser, HiddenUserProfile, M, M2MFrom,
-    M2MTo, MRNull, Origin, Parent, R, RChild, RChildChild, Referrer, S, T,
+    B1, B2, MR, A, Avatar, Base, Child, DeleteBottom, DeleteTop, GenericB1,
+    GenericB2, GenericDeleteBottom, HiddenUser, HiddenUserProfile, M, M2MFrom,
+    M2MTo, MRNull, Origin, P, Parent, R, RChild, RChildChild, Referrer, S, T,
     User, create_a, get_default_r,
 )
 
@@ -146,6 +147,87 @@ class OnDeleteTests(TestCase):
         a = A.objects.get(pk=a.pk)
         self.assertIsNone(a.o2o_setnull)
 
+    def test_restrict(self):
+        a = create_a('restrict')
+        msg = (
+            "Cannot delete some instances of model 'R' because they are "
+            "referenced through a restricted foreign key: 'A.restrict'."
+        )
+        with self.assertRaisesMessage(RestrictedError, msg):
+            a.restrict.delete()
+
+    def test_restrict_path_cascade_indirect(self):
+        a = create_a('restrict')
+        a.restrict.p = P.objects.create()
+        a.restrict.save()
+        msg = (
+            "Cannot delete some instances of model 'R' because they are "
+            "referenced through a restricted foreign key: 'A.restrict'."
+        )
+        with self.assertRaisesMessage(RestrictedError, msg):
+            a.restrict.p.delete()
+        # Object referenced also with CASCADE relationship can be deleted.
+        a.cascade.p = a.restrict.p
+        a.cascade.save()
+        a.restrict.p.delete()
+        self.assertFalse(A.objects.filter(name='restrict').exists())
+        self.assertFalse(R.objects.filter(pk=a.restrict_id).exists())
+
+    def test_restrict_path_cascade_direct(self):
+        a = create_a('restrict')
+        a.restrict.p = P.objects.create()
+        a.restrict.save()
+        a.cascade_p = a.restrict.p
+        a.save()
+        a.restrict.p.delete()
+        self.assertFalse(A.objects.filter(name='restrict').exists())
+        self.assertFalse(R.objects.filter(pk=a.restrict_id).exists())
+
+    def test_restrict_path_cascade_indirect_diamond(self):
+        delete_top = DeleteTop.objects.create()
+        b1 = B1.objects.create(delete_top=delete_top)
+        b2 = B2.objects.create(delete_top=delete_top)
+        DeleteBottom.objects.create(b1=b1, b2=b2)
+        msg = (
+            "Cannot delete some instances of model 'B1' because they are "
+            "referenced through a restricted foreign key: 'DeleteBottom.b1'."
+        )
+        with self.assertRaisesMessage(RestrictedError, msg):
+            b1.delete()
+        self.assertTrue(DeleteTop.objects.exists())
+        self.assertTrue(B1.objects.exists())
+        self.assertTrue(B2.objects.exists())
+        self.assertTrue(DeleteBottom.objects.exists())
+        # Object referenced also with CASCADE relationship can be deleted.
+        delete_top.delete()
+        self.assertFalse(DeleteTop.objects.exists())
+        self.assertFalse(B1.objects.exists())
+        self.assertFalse(B2.objects.exists())
+        self.assertFalse(DeleteBottom.objects.exists())
+
+    def test_restrict_gfk_no_fast_delete(self):
+        delete_top = DeleteTop.objects.create()
+        generic_b1 = GenericB1.objects.create(generic_delete_top=delete_top)
+        generic_b2 = GenericB2.objects.create(generic_delete_top=delete_top)
+        GenericDeleteBottom.objects.create(generic_b1=generic_b1, generic_b2=generic_b2)
+        msg = (
+            "Cannot delete some instances of model 'GenericB1' because they "
+            "are referenced through a restricted foreign key: "
+            "'GenericDeleteBottom.generic_b1'."
+        )
+        with self.assertRaisesMessage(RestrictedError, msg):
+            generic_b1.delete()
+        self.assertTrue(DeleteTop.objects.exists())
+        self.assertTrue(GenericB1.objects.exists())
+        self.assertTrue(GenericB2.objects.exists())
+        self.assertTrue(GenericDeleteBottom.objects.exists())
+        # Object referenced also with CASCADE relationship can be deleted.
+        delete_top.delete()
+        self.assertFalse(DeleteTop.objects.exists())
+        self.assertFalse(GenericB1.objects.exists())
+        self.assertFalse(GenericB2.objects.exists())
+        self.assertFalse(GenericDeleteBottom.objects.exists())
+
 
 class DeletionTests(TestCase):