Ticket #18823: m2m_through_field.patch

django/db/models/fields/related.py

@@ -558 +558 @@
             self.reverse = reverse
             self.through = through
             self.prefetch_cache_name = prefetch_cache_name
-            self._pk_val = self.instance.pk
+            self._pk_val = self._get_fk_val(self.instance, source_field_name)
             if self._pk_val is None:
                 raise ValueError("%r instance needs to have a primary key value before a many-to-many relationship can be used." % instance.__class__.__name__)
 
+        def _get_fk_val(self, obj, field_name):
+            # Get's the correct value for this relationship
+            # takes to_field into account
+            fk = self.through._meta.get_field(field_name)
+            value = obj.pk
+            if fk.rel.field_name and fk.rel.field_name != fk.rel.to._meta.pk.attname:
+                attname = fk.rel.get_related_field().get_attname()
+                value = fk.get_prep_lookup('exact', getattr(obj, attname))
+            return value
+
         def get_query_set(self):
             try:
                 return self.instance._prefetched_objects_cache[self.prefetch_cache_name]
@@ -662 +672 @@
                         if not router.allow_relation(obj, self.instance):
                            raise ValueError('Cannot add "%r": instance is on database "%s", value is on database "%s"' %
                                                (obj, self.instance._state.db, obj._state.db))
-                        new_ids.add(obj.pk)
+                        new_ids.add(self._get_fk_val(obj, target_field_name))
                     elif isinstance(obj, Model):
                         raise TypeError("'%s' instance expected, got %r" % (self.model._meta.object_name, obj))
                     else:
@@ -689 +699 @@
                     })
                     for obj_id in new_ids
                 ])
+
                 if self.reverse or source_field_name == self.source_field_name:
                     # Don't send the signal when we are inserting the
                     # duplicate data row for symmetrical reverse entries.
@@ -707 +718 @@
                 old_ids = set()
                 for obj in objs:
                     if isinstance(obj, self.model):
-                        old_ids.add(obj.pk)
+                        old_ids.add(self._get_fk_val(obj, target_field_name))
                     else:
                         old_ids.add(obj)
                 # Work out what DB we're operating on

tests/regressiontests/m2m_through_regress/models.py

@@ -80 +80 @@
     car = models.ForeignKey('Car', to_field='make')
     driver = models.ForeignKey('Driver', to_field='name')
 
+    class Meta:
+        auto_created = Car
+
     def __str__(self):
         return "pk=%s car=%s driver=%s" % (str(self.pk), self.car, self.driver)

tests/regressiontests/m2m_through_regress/tests.py

@@ -136 +136 @@
             ["<Car: Toyota>"]
             )
 
+    def test_to_field_clear_reverse(self):
+        self.driver.car_set.clear()
+        self.assertQuerysetEqual(
+            self.driver.car_set.all(),[])
+
+    def test_to_field_clear(self):
+        self.car.drivers.clear()
+        self.assertQuerysetEqual(
+            self.car.drivers.all(),[])
+
+class AutoToFieldThroughTests(TestCase):
+    def setUp(self):
+        self.car = Car.objects.create(make="Toyota")
+        self.driver = Driver.objects.create(name="Ryan Briscoe")
+
+    def test_add(self):
+        self.assertQuerysetEqual(
+            self.car.drivers.all(),[])
+        self.car.drivers.add(self.driver)
+        self.assertQuerysetEqual(
+            self.car.drivers.all(),
+            ["<Driver: Ryan Briscoe>"]
+            )
+
+    def test_add_reverse(self):
+        self.assertQuerysetEqual(
+            self.driver.car_set.all(),[])
+        self.driver.car_set.add(self.car)
+        self.assertQuerysetEqual(
+            self.driver.car_set.all(),
+            ["<Car: Toyota>"]
+            )
+
+    def test_remove(self):
+        CarDriver.objects.create(car=self.car, driver=self.driver)
+        self.assertQuerysetEqual(
+            self.car.drivers.all(),
+            ["<Driver: Ryan Briscoe>"]
+            )
+        self.car.drivers.remove(self.driver)
+        self.assertQuerysetEqual(
+            self.car.drivers.all(),[])
+
+
+    def test_remove_reverse(self):
+        CarDriver.objects.create(car=self.car, driver=self.driver)
+        self.assertQuerysetEqual(
+            self.driver.car_set.all(),
+            ["<Car: Toyota>"]
+            )
+        self.driver.car_set.remove(self.car)
+        self.assertQuerysetEqual(
+            self.driver.car_set.all(),[])
+
+
 class ThroughLoadDataTestCase(TestCase):
     fixtures = ["m2m_through"]