Correctly handle virtual related fields.

tenancy/models.py

@@ -231,14 +231,17 @@ def __new__(cls, name, bases, attrs):
                 cls.references[model] = cls.reference(model, Meta, related_names)
                 opts = model._meta
                 # Validate related name of related fields.
-                for field in opts.local_fields:
-                    if field.rel:
+                for field in (opts.local_fields + opts.virtual_fields):
+                    rel = getattr(field, 'rel', None)
+                    if rel:
                         cls.validate_related_name(field, field.rel.to, model)
                         # Replace and store the current `on_delete` value to
                         # make sure non-tenant models are not collected on
                         # deletion.
-                        field.rel._on_delete = field.rel.on_delete
-                        field.rel.on_delete = DO_NOTHING
+                        on_delete = rel.on_delete
+                        if on_delete is not DO_NOTHING:
+                            rel._on_delete = on_delete
+                            rel.on_delete = DO_NOTHING
                 for m2m in opts.local_many_to_many:
                     rel = m2m.rel
                     to = rel.to
@@ -389,12 +392,16 @@ def abstract_tenant_model_factory(self, tenant):
             local_ptr = self._meta.parents[parent._for_tenant_model]
             ptr.name = None
             ptr.set_attributes_from_name(local_ptr.name)
-
-        # Add the local fields of this class
-        local_fields = self._meta.local_fields + self._meta.local_many_to_many
-        for local_field in local_fields:
-            field = copy.deepcopy(local_field)
-            rel = field.rel
+        # Add copy of the fields to cloak the inherited ones.
+        fields = (
+            copy.deepcopy(field) for field in (
+                self._meta.local_fields +
+                self._meta.local_many_to_many +
+                self._meta.virtual_fields
+            )
+        )
+        for field in fields:
+            rel = getattr(field, 'rel', None)
             if rel:
                 # Make sure related fields pointing to tenant models are
                 # pointing to their tenant specific counterpart.
@@ -419,10 +426,11 @@ def abstract_tenant_model_factory(self, tenant):
                 if isinstance(field, models.ManyToManyField):
                     through = field.rel.through
                     rel.through = self.references[through].for_tenant(tenant)
-                else:
-                    # Re-assign the correct `on_delete` that was swapped for
-                    # `DO_NOTHING` to prevent non-tenant model collection.
-                    rel.on_delete = rel._on_delete
+                # Re-assign the correct `on_delete` that was swapped for
+                # `DO_NOTHING` to prevent non-tenant model collection.
+                on_delete = getattr(rel, '_on_delete', None)
+                if on_delete:
+                    rel.on_delete = on_delete
             field.contribute_to_class(model, field.name)
 
         return model

tenancy/tests/models.py

@@ -137,7 +137,7 @@ class TenantMeta:
 
 
 class M2MSpecific(TenantModel):
-    related = models.ForeignKey('RelatedTenantModel')
+    related = models.ForeignKey('RelatedTenantModel', null=True)
     specific = models.ForeignKey(
         SpecificModel, related_name="%(app_label)s_%(class)s_related"
     )
@@ -230,3 +230,15 @@ class MutableModelSubclass(MutableModel):
 
         class NonMutableModel(TenantModel):
             mutable_fk = models.ForeignKey(MutableModel, related_name='non_mutables')
+
+
+try:
+    from django.db.models.fields.related import ForeignObject
+except ImportError:
+    pass
+else:
+    ForeignObject(
+        RelatedTenantModel, ['specific'], ['fk'], related_name='+'
+    ).contribute_to_class(
+        M2MSpecific, 'specific_related_fk', virtual_only=True
+    )

tenancy/tests/test_models.py

@@ -6,9 +6,9 @@
 import sys
 # TODO: Remove when support for Python 2.6 is dropped
 if sys.version_info >= (2, 7):
-    from unittest import skipIf
+    from unittest import skipIf, skipUnless
 else:
-    from django.utils.unittest import skipIf
+    from django.utils.unittest import skipIf, skipUnless
 import weakref
 
 from django.contrib.contenttypes.models import ContentType
@@ -525,6 +525,19 @@ def test_signals(self):
                 ]
             )
 
+    @skipUnless(hasattr(django_models, 'ForeignObject'),
+                'Foreign object is not present is this version of Django.')
+    def test_virtual_foreign_object(self):
+        """
+        Make sure a virtual foreign object pointing to a tenant specific
+        model is correctly handled.
+        """
+        for tenant in Tenant.objects.all():
+            specific = tenant.specificmodels.create()
+            related = tenant.related_tenant_models.create(fk=specific)
+            m2m_specific = tenant.m2m_specifics.create(specific=specific)
+            self.assertEqual(m2m_specific.specific_related_fk, related)
+
 
 class NonTenantModelTest(TransactionTestCase):
     def test_fk_to_tenant(self):