Commit c5def493 authored by Andrew Godwin's avatar Andrew Godwin
Browse files

Fixed #23835: Changed circular dependency in DFS to be less infinite

parent c1584e1d

django/db/migrations/graph.py

+2 −2
Original line number Diff line number Diff line
@@ -116,8 +116,8 @@ class MigrationGraph(object): 
            visited.insert(0, node)

            children = sorted(get_children(node))



            if not children:

                path = []

            if path[-1] == node:

                path.pop()



            stack = children + stack

tests/migrations/test_graph.py

+27 −0
Original line number Diff line number Diff line
@@ -188,3 +188,30 @@ class GraphTests(TestCase): 
        msg = "Migration app_a.0002 dependencies reference nonexistent child node ('app_a', '0002')"

        with self.assertRaisesMessage(NodeNotFoundError, msg):

            graph.add_dependency("app_a.0002", ("app_a", "0002"), ("app_a", "0001"))



    def test_infinite_loop(self):

        """

        Tests a complex dependency graph:



        app_a:        0001 <-

                             \

        app_b:        0001 <- x 0002 <-

                       /               \

        app_c:   0001<-  <------------- x 0002



        And apply sqashing on app_c.

        """

        graph = MigrationGraph()



        graph.add_node(("app_a", "0001"), None)

        graph.add_node(("app_b", "0001"), None)

        graph.add_node(("app_b", "0002"), None)

        graph.add_node(("app_c", "0001_squashed_0002"), None)



        graph.add_dependency("app_b.0001", ("app_b", "0001"), ("app_c", "0001_squashed_0002"))

        graph.add_dependency("app_b.0002", ("app_b", "0002"), ("app_a", "0001"))

        graph.add_dependency("app_b.0002", ("app_b", "0002"), ("app_b", "0001"))

        graph.add_dependency("app_c.0001_squashed_0002", ("app_c", "0001_squashed_0002"), ("app_b", "0002"))



        with self.assertRaises(CircularDependencyError):

            graph.forwards_plan(("app_c", "0001_squashed_0002"))