Issue #22410: Module level functions in the re module now cache compiled

locale-dependent regular expressions taking into account the locale.

Lib/re.py

@@ -104,6 +104,7 @@ This module also defines an exception 'error'.
 import sys
 import sre_compile
 import sre_parse
+import _locale
 
 # public symbols
 __all__ = [ "match", "search", "sub", "subn", "split", "findall",
@@ -229,9 +230,12 @@ def _compile(*key):
     bypass_cache = flags & DEBUG
     if not bypass_cache:
         cachekey = (type(key[0]),) + key
-        p = _cache.get(cachekey)
-        if p is not None:
-            return p
+        try:
+            p, loc = _cache[cachekey]
+            if loc is None or loc == _locale.setlocale(_locale.LC_CTYPE):
+                return p
+        except KeyError:
+            pass
     if isinstance(pattern, _pattern_type):
         if flags:
             raise ValueError('Cannot process flags argument with a compiled pattern')
@@ -245,7 +249,11 @@ def _compile(*key):
     if not bypass_cache:
         if len(_cache) >= _MAXCACHE:
             _cache.clear()
-        _cache[cachekey] = p
+        if p.flags & LOCALE:
+            loc = _locale.setlocale(_locale.LC_CTYPE)
+        else:
+            loc = None
+        _cache[cachekey] = p, loc
     return p
 
 def _compile_repl(*key):

Lib/test/test_re.py

 from test.test_support import verbose, run_unittest, import_module
 from test.test_support import precisionbigmemtest, _2G, cpython_only
 from test.test_support import captured_stdout, have_unicode, requires_unicode, u
+import locale
 import re
 from re import Scanner
 import sre_constants
@@ -975,6 +976,42 @@ subpattern None
         self.assertEqual(re.match("(foo)", "foo").group(1L), "foo")
         self.assertRaises(IndexError, re.match("", "").group, sys.maxint + 1)
 
+    def test_locale_caching(self):
+        # Issue #22410
+        oldlocale = locale.setlocale(locale.LC_CTYPE)
+        self.addCleanup(locale.setlocale, locale.LC_CTYPE, oldlocale)
+        for loc in 'en_US.iso88591', 'en_US.utf8':
+            try:
+                locale.setlocale(locale.LC_CTYPE, loc)
+            except locale.Error:
+                # Unsupported locale on this system
+                self.skipTest('test needs %s locale' % loc)
+
+        re.purge()
+        self.check_en_US_iso88591()
+        self.check_en_US_utf8()
+        re.purge()
+        self.check_en_US_utf8()
+        self.check_en_US_iso88591()
+
+    def check_en_US_iso88591(self):
+        locale.setlocale(locale.LC_CTYPE, 'en_US.iso88591')
+        self.assertTrue(re.match(b'\xc5\xe5', b'\xc5\xe5', re.L|re.I))
+        self.assertTrue(re.match(b'\xc5', b'\xe5', re.L|re.I))
+        self.assertTrue(re.match(b'\xe5', b'\xc5', re.L|re.I))
+        self.assertTrue(re.match(b'(?Li)\xc5\xe5', b'\xc5\xe5'))
+        self.assertTrue(re.match(b'(?Li)\xc5', b'\xe5'))
+        self.assertTrue(re.match(b'(?Li)\xe5', b'\xc5'))
+
+    def check_en_US_utf8(self):
+        locale.setlocale(locale.LC_CTYPE, 'en_US.utf8')
+        self.assertTrue(re.match(b'\xc5\xe5', b'\xc5\xe5', re.L|re.I))
+        self.assertIsNone(re.match(b'\xc5', b'\xe5', re.L|re.I))
+        self.assertIsNone(re.match(b'\xe5', b'\xc5', re.L|re.I))
+        self.assertTrue(re.match(b'(?Li)\xc5\xe5', b'\xc5\xe5'))
+        self.assertIsNone(re.match(b'(?Li)\xc5', b'\xe5'))
+        self.assertIsNone(re.match(b'(?Li)\xe5', b'\xc5'))
+
 
 def run_re_tests():
     from test.re_tests import tests, SUCCEED, FAIL, SYNTAX_ERROR

Misc/NEWS

@@ -37,6 +37,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #22410: Module level functions in the re module now cache compiled
+  locale-dependent regular expressions taking into account the locale.
+
 - Issue #8876: distutils now falls back to copying files when hard linking
   doesn't work.  This allows use with special filesystems such as VirtualBox
   shared folders.