bpo-47080: Use atomic groups to simplify fnmatch (GH-32029)

Use re's new atomic groups to greatly simplify the construction of worst-case linear-time patterns.

1 files changed, 2 insertions, 10 deletions

diff --git a/Lib/test/test_fnmatch.py b/Lib/test/test_fnmatch.py
index 10668e4..ca695d6 100644
--- a/Lib/test/test_fnmatch.py
+++ b/Lib/test/test_fnmatch.py
@@ -124,17 +124,9 @@ class TranslateTestCase(unittest.TestCase):
         self.assertEqual(translate('A*********?[?]?'), r'(?s:A.*.[?].)\Z')
         # fancy translation to prevent exponential-time match failure
         t = translate('**a*a****a')
-        digits = re.findall(r'\d+', t)
-        self.assertEqual(len(digits), 4)
-        self.assertEqual(digits[0], digits[1])
-        self.assertEqual(digits[2], digits[3])
-        g1 = f"g{digits[0]}"  # e.g., group name "g4"
-        g2 = f"g{digits[2]}"  # e.g., group name "g5"
-        self.assertEqual(t,
-         fr'(?s:(?=(?P<{g1}>.*?a))(?P={g1})(?=(?P<{g2}>.*?a))(?P={g2}).*a)\Z')
+        self.assertEqual(t, r'(?s:(?>.*?a)(?>.*?a).*a)\Z')
         # and try pasting multiple translate results - it's an undocumented
-        # feature that this works; all the pain of generating unique group
-        # names across calls exists to support this
+        # feature that this works
         r1 = translate('**a**a**a*')
         r2 = translate('**b**b**b*')
         r3 = translate('*c*c*c*')