Commit 12385a5f authored by Robert Stapenhurst's avatar Robert Stapenhurst Committed by Tim Graham
Browse files

Fixed #21763 -- Added an error msg for missing methods on ManyRelatedManager. 

Attempting to add() and remove() an object related by a 'through' model
now raises more descriptive AttributeErrors, in line with set and
create().
parent 29345390

django/db/models/fields/related.py

+23 −14
Original line number Diff line number Diff line
@@ -867,10 +867,13 @@ def create_many_related_manager(superclass, rel): 
                    False,

                    self.prefetch_cache_name)



        # If the ManyToMany relation has an intermediary model,

        # the add and remove methods do not exist.

        if rel.through._meta.auto_created:

        def add(self, *objs):

            if not rel.through._meta.auto_created:

                opts = self.through._meta

                raise AttributeError(

                    "Cannot use add() on a ManyToManyField which specifies an intermediary model. Use %s.%s's Manager instead." %

                    (opts.app_label, opts.object_name)

                )

            self._add_items(self.source_field_name, self.target_field_name, *objs)



            # If this is a symmetrical m2m relation to self, add the mirror entry in the m2m table
@@ -879,6 +882,12 @@ def create_many_related_manager(superclass, rel): 
        add.alters_data = True



        def remove(self, *objs):

            if not rel.through._meta.auto_created:

                opts = self.through._meta

                raise AttributeError(

                    "Cannot use remove() on a ManyToManyField which specifies an intermediary model. Use %s.%s's Manager instead." %

                    (opts.app_label, opts.object_name)

                )

            self._remove_items(self.source_field_name, self.target_field_name, *objs)

        remove.alters_data = True

tests/m2m_through/tests.py

+56 −15
Original line number Diff line number Diff line
@@ -68,12 +68,24 @@ class M2mThroughTests(TestCase): 


    def test_forward_descriptors(self):

        # Due to complications with adding via an intermediary model,

        # the add method is not provided.

        self.assertRaises(AttributeError, lambda: self.rock.members.add(self.bob))

        # the add method raises an error.

        self.assertRaisesMessage(

            AttributeError,

            'Cannot use add() on a ManyToManyField which specifies an intermediary model',

            lambda: self.rock.members.add(self.bob)

        )

        # Create is also disabled as it suffers from the same problems as add.

        self.assertRaises(AttributeError, lambda: self.rock.members.create(name='Anne'))

        # Remove has similar complications, and is not provided either.

        self.assertRaises(AttributeError, lambda: self.rock.members.remove(self.jim))

        self.assertRaisesMessage(

            AttributeError,

            'Cannot use create() on a ManyToManyField which specifies an intermediary model',

            lambda: self.rock.members.create(name='Anne')

        )

        # Remove has similar complications, and it also raises an error.

        self.assertRaisesMessage(

            AttributeError,

            'Cannot use remove() on a ManyToManyField which specifies an intermediary model',

            lambda: self.rock.members.remove(self.jim)

        )



        m1 = Membership.objects.create(person=self.jim, group=self.rock)

        m2 = Membership.objects.create(person=self.jane, group=self.rock)
@@ -93,9 +105,17 @@ class M2mThroughTests(TestCase): 
            []

        )



        # Assignment should not work with models specifying a through model for many of

        # the same reasons as adding.

        self.assertRaises(AttributeError, setattr, self.rock, "members", backup)

        # Assignment should not work with models specifying a through model for

        # many of the same reasons as adding.

        self.assertRaisesMessage(

            AttributeError,

            'Cannot set values on a ManyToManyField which specifies an intermediary model',

            setattr,

            self.rock,

            "members",

            backup

        )



        # Let's re-save those instances that we've cleared.

        m1.save()

        m2.save()
@@ -111,11 +131,25 @@ class M2mThroughTests(TestCase): 
    def test_reverse_descriptors(self):

        # Due to complications with adding via an intermediary model,

        # the add method is not provided.

        self.assertRaises(AttributeError, lambda: self.bob.group_set.add(self.rock))

        self.assertRaisesMessage(

            AttributeError,

            'Cannot use add() on a ManyToManyField which specifies an intermediary model',

            lambda: self.bob.group_set.add(self.rock)

        )



        # Create is also disabled as it suffers from the same problems as add.

        self.assertRaises(AttributeError, lambda: self.bob.group_set.create(name="funk"))

        self.assertRaisesMessage(

            AttributeError,

            'Cannot use create() on a ManyToManyField which specifies an intermediary model',

            lambda: self.bob.group_set.create(name="funk")

        )



        # Remove has similar complications, and is not provided either.

        self.assertRaises(AttributeError, lambda: self.jim.group_set.remove(self.rock))

        self.assertRaisesMessage(

            AttributeError,

            'Cannot use remove() on a ManyToManyField which specifies an intermediary model',

            lambda: self.jim.group_set.remove(self.rock)

        )



        m1 = Membership.objects.create(person=self.jim, group=self.rock)

        m2 = Membership.objects.create(person=self.jim, group=self.roll)
@@ -133,11 +167,18 @@ class M2mThroughTests(TestCase): 
            self.jim.group_set.all(),

            []

        )

        # Assignment should not work with models specifying a through model for many of

        # the same reasons as adding.

        self.assertRaises(AttributeError, setattr, self.jim, "group_set", backup)

        # Let's re-save those instances that we've cleared.

        # Assignment should not work with models specifying a through model for

        # many of the same reasons as adding.

        self.assertRaisesMessage(

            AttributeError,

            'Cannot set values on a ManyToManyField which specifies an intermediary model',

            setattr,

            self.jim,

            "group_set",

            backup

        )



        # Let's re-save those instances that we've cleared.

        m1.save()

        m2.save()

        # Verifying that those instances were re-saved successfully.