id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
33410	captureOnCommitCallbacks executes callbacks multiple times.	Petter Friberg	Petter Friberg	"When recursively adding multiple on commit callbacks, `captureOnCommitCallbacks` executes some callbacks multiple times. Below is a test case to reproduce the error.

Patch: https://github.com/django/django/pull/15285

{{{
#!div style=""font-size: 80%""
  {{{#!python
    def test_execute_tree(self):
        """"""
        A visualisation of the callback tree tested. Each node is expected to be visited
        only once. The child count of a node symbolises the amount of on commit
        callbacks.

        root
        └── branch_1
            ├── branch_2
            │   ├── leaf_1
            │   └── leaf_2
            └── leaf_3
        """"""
        (
            branch_1_call_counter,
            branch_2_call_counter,
            leaf_1_call_counter,
            leaf_2_call_counter,
            leaf_3_call_counter,
        ) = [itertools.count(start=1) for _ in range(5)]

        def leaf_3():
            next(leaf_3_call_counter)

        def leaf_2():
            next(leaf_2_call_counter)

        def leaf_1():
            next(leaf_1_call_counter)

        def branch_2():
            next(branch_2_call_counter)
            transaction.on_commit(leaf_1)
            transaction.on_commit(leaf_2)

        def branch_1():
            next(branch_1_call_counter)
            transaction.on_commit(branch_2)
            transaction.on_commit(leaf_3)

        with self.captureOnCommitCallbacks(execute=True) as callbacks:
            with transaction.atomic():
                transaction.on_commit(branch_1)

        # Every counter shall only have been called once, starting at 1; next value then
        # has to be 2
        self.assertEqual(next(branch_1_call_counter), 2)
        self.assertEqual(next(branch_2_call_counter), 2)
        self.assertEqual(next(leaf_1_call_counter), 2)
        self.assertEqual(next(leaf_2_call_counter), 2)
        self.assertEqual(next(leaf_3_call_counter), 2)
        # Make sure all calls can be seen and the execution order is correct
        self.assertEqual(
            [(id(callback), callback.__name__) for callback in callbacks],
            [
                (id(branch_1), ""branch_1""),
                (id(branch_2), ""branch_2""),
                (id(leaf_3), ""leaf_3""),
                (id(leaf_1), ""leaf_1""),
                (id(leaf_2), ""leaf_2""),
            ],
        )
  }}}
}}}"	Bug	closed	Testing framework	4.0	Release blocker	fixed	captureOnCommitCallbacks	Eugene Morozov Adam Johnson	Ready for checkin	1	0	0	0	0	0