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gh-106052: Fix bug in the matching of possessive quantifiers · python/cpython@89bf9dc · GitHub

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Commit 89bf9dc

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serhiy-storchaka
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gh-106052: Fix bug in the matching of possessive quantifiers
It did not work in the case of a subpattern containing backtracking. Temporary implement possessive quantifiers as equivalent greedy qualifiers in atomic groups.
1 parent 24fb627 commit 89bf9dc

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‎Lib/re/_compiler.py‎

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@@ -100,6 +100,13 @@ def _compile(code, pattern, flags):
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emit(ANY_ALL)
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else:
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emit(ANY)
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elif op is POSSESSIVE_REPEAT:
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# gh-106052: Possessive quantifiers do not work when the
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# subpattern contains backtracking, i.e. "(?:ab?c)*+".
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# Implement it as equivalent greedy qualifier in atomic group.
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p = [(MAX_REPEAT, av)]
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p = [(ATOMIC_GROUP, p)]
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_compile(code, p, flags)
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elif op in REPEATING_CODES:
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if _simple(av[2]):
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emit(REPEATING_CODES[op][2])

‎Lib/test/test_re.py‎

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@@ -2398,6 +2398,16 @@ def test_bug_gh91616(self):
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self.assertTrue(re.fullmatch(r'(?s:(?>.*?\.).*)\Z', "a.txt")) # reproducer
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self.assertTrue(re.fullmatch(r'(?s:(?=(?P<g0>.*?\.))(?P=g0).*)\Z', "a.txt"))
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def test_bug_gh106052(self):
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self.assertEqual(re.match("(?>(?:ab?c)+)", "aca").span(), (0, 2))
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self.assertEqual(re.match("(?:ab?c)++", "aca").span(), (0, 2))
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self.assertEqual(re.match("(?>(?:ab?c)*)", "aca").span(), (0, 2))
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self.assertEqual(re.match("(?:ab?c)*+", "aca").span(), (0, 2))
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self.assertEqual(re.match("(?>(?:ab?c)?)", "a").span(), (0, 0))
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self.assertEqual(re.match("(?:ab?c)?+", "a").span(), (0, 0))
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self.assertEqual(re.match("(?>(?:ab?c){1,3})", "aca").span(), (0, 2))
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self.assertEqual(re.match("(?:ab?c){1,3}+", "aca").span(), (0, 2))
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@unittest.skipIf(multiprocessing is None, 'test requires multiprocessing')
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def test_regression_gh94675(self):
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pattern = re.compile(r'(?<=[({}])(((//[^\n]*)?[\n])([\000-\040])*)*'
@@ -2491,6 +2501,7 @@ def test_atomic_group(self):
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17: SUCCESS
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''')
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@unittest.expectedFailure # gh-106052
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def test_possesive_repeat_one(self):
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self.assertEqual(get_debug_out(r'a?+'), '''\
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POSSESSIVE_REPEAT 0 1
@@ -2503,6 +2514,7 @@ def test_possesive_repeat_one(self):
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12: SUCCESS
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''')
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@unittest.expectedFailure # gh-106052
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def test_possesive_repeat(self):
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self.assertEqual(get_debug_out(r'(?:ab)?+'), '''\
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POSSESSIVE_REPEAT 0 1

‎Misc/NEWS.d/next/Library/2023-07-07-14-52-31.gh-issue-106052.ak8nbs.rst‎

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@@ -0,0 +1,2 @@
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:mod:`re` module: fix the matching of possessive quantifiers in the case of
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a subpattern containing backtracking.

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