bpo-32775: Fix regular expression warnings in fnmatch. (#5583)

fnmatch.translate() no longer produces patterns which contain set
operations.

Sets starting with '[' or containing '--', '&&', '~~' or '||' will
be interpreted differently in regular expressions in future versions.
Currently they emit warnings. fnmatch.translate() now avoids producing
patterns containing such sets by accident.

1 files changed, 12 insertions, 0 deletions

diff --git a/Lib/test/test_fnmatch.py b/Lib/test/test_fnmatch.py
index 78245c3..55f9f0d 100644
--- a/Lib/test/test_fnmatch.py
+++ b/Lib/test/test_fnmatch.py
@@ -2,6 +2,7 @@
 
 import unittest
 import os
+import warnings
 
 from fnmatch import fnmatch, fnmatchcase, translate, filter
 
@@ -83,6 +84,17 @@ class FnmatchTestCase(unittest.TestCase):
         check('usr/bin', 'usr\\bin', normsep)
         check('usr\\bin', 'usr\\bin')
 
+    def test_warnings(self):
+        with warnings.catch_warnings():
+            warnings.simplefilter('error', Warning)
+            check = self.check_match
+            check('[', '[[]')
+            check('&', '[a&&b]')
+            check('|', '[a||b]')
+            check('~', '[a~~b]')
+            check(',', '[a-z+--A-Z]')
+            check('.', '[a-z--/A-Z]')
+
 
 class TranslateTestCase(unittest.TestCase):