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gh-130914: Make graphlib.TopologicalSorter.prepare() idempotent (#131317)

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Closes #130914: Make graphlib.TopologicalSorter.prepare() idempotent

Relax the rules so that `.prepare()` can be called multiple times, provided that no work has been passed out by `.get_ready()` yet.
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Daniel Pope 2025-03-18 21:28:00 +00:00 • committed by GitHub
parent f819900245
commit c1b42db9e4
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6 changed files with 44 additions and 7 deletions
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14
Lib/test/test_graphlib.py
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@ -140,9 +140,21 @@ def test_calls_before_prepare(self):
def test_prepare_multiple_times(self):
ts = graphlib.TopologicalSorter()
ts.prepare()
with self.assertRaisesRegex(ValueError, r"cannot prepare\(\) more than once"):
ts.prepare()
def test_prepare_after_pass_out(self):
ts = graphlib.TopologicalSorter({'a': 'bc'})
ts.prepare()
self.assertEqual(set(ts.get_ready()), {'b', 'c'})
with self.assertRaisesRegex(ValueError, r"cannot prepare\(\) after starting sort"):
ts.prepare()
def test_prepare_cycleerror_each_time(self):
ts = graphlib.TopologicalSorter({'a': 'b', 'b': 'a'})
for attempt in range(1, 4):
with self.assertRaises(graphlib.CycleError, msg=f"{attempt=}"):
ts.prepare()
def test_invalid_nodes_in_done(self):
ts = graphlib.TopologicalSorter()
ts.add(1, 2, 3, 4)