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

This commit is contained in:
Andrew Godwin 2014-11-15 17:37:13 +01:00
parent c1584e1df4
commit c5def493d0
2 changed files with 29 additions and 2 deletions
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4
django/db/migrations/graph.py
View File

@ -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

27
tests/migrations/test_graph.py
View File

@ -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"))