gh-53203: Improve tests for strptime() (GH-125090)

Run them with different locales and different date and time.

Add the @run_with_locales() decorator to run the test with multiple
locales.

Improve the run_with_locale() context manager/decorator -- it now
catches only expected exceptions and reports the test as skipped if no
appropriate locale is available.

Author: serhiy-storchaka

Lib/test/pickletester.py

@@ -26,7 +26,7 @@
 from test import support
 from test.support import os_helper
 from test.support import (
-    TestFailed, run_with_locale, no_tracing,
+    TestFailed, run_with_locales, no_tracing,
     _2G, _4G, bigmemtest
     )
 from test.support.import_helper import forget
@@ -2895,7 +2895,7 @@ def test_float(self):
                 got = self.loads(pickle)
                 self.assert_is_copy(value, got)
 
-    @run_with_locale('LC_ALL', 'de_DE', 'fr_FR')
+    @run_with_locales('LC_ALL', 'de_DE', 'fr_FR', '')
     def test_float_format(self):
         # make sure that floats are formatted locale independent with proto 0
         self.assertEqual(self.dumps(1.2, 0)[0:3], b'F1.')

Lib/test/support/__init__.py

@@ -930,8 +930,8 @@ def check_sizeof(test, o, size):
     test.assertEqual(result, size, msg)
 
 #=======================================================================
-# Decorator for running a function in a different locale, correctly resetting
-# it afterwards.
+# Decorator/context manager for running a code in a different locale,
+# correctly resetting it afterwards.
 
 @contextlib.contextmanager
 def run_with_locale(catstr, *locales):
@@ -942,23 +942,68 @@ def run_with_locale(catstr, *locales):
     except AttributeError:
         # if the test author gives us an invalid category string
         raise
-    except:
+    except Exception:
         # cannot retrieve original locale, so do nothing
         locale = orig_locale = None
+        if '' not in locales:
+            raise unittest.SkipTest('no locales')
     else:
         for loc in locales:
             try:
                 locale.setlocale(category, loc)
                 break
-            except:
+            except locale.Error:
                 pass
+        else:
+            if '' not in locales:
+                raise unittest.SkipTest(f'no locales {locales}')
 
     try:
         yield
     finally:
         if locale and orig_locale:
             locale.setlocale(category, orig_locale)
 
+#=======================================================================
+# Decorator for running a function in multiple locales (if they are
+# availasble) and resetting the original locale afterwards.
+
+def run_with_locales(catstr, *locales):
+    def deco(func):
+        @functools.wraps(func)
+        def wrapper(self, /, *args, **kwargs):
+            dry_run = '' in locales
+            try:
+                import locale
+                category = getattr(locale, catstr)
+                orig_locale = locale.setlocale(category)
+            except AttributeError:
+                # if the test author gives us an invalid category string
+                raise
+            except Exception:
+                # cannot retrieve original locale, so do nothing
+                pass
+            else:
+                try:
+                    for loc in locales:
+                        with self.subTest(locale=loc):
+                            try:
+                                locale.setlocale(category, loc)
+                            except locale.Error:
+                                self.skipTest(f'no locale {loc!r}')
+                            else:
+                                dry_run = False
+                                func(self, *args, **kwargs)
+                finally:
+                    locale.setlocale(category, orig_locale)
+            if dry_run:
+                # no locales available, so just run the test
+                # with the current locale
+                with self.subTest(locale=None):
+                    func(self, *args, **kwargs)
+        return wrapper
+    return deco
+
 #=======================================================================
 # Decorator for running a function in a specific timezone, correctly
 # resetting it afterwards.

Lib/test/test_codecs.py

@@ -2,7 +2,6 @@
 import contextlib
 import copy
 import io
-import locale
 import pickle
 import sys
 import unittest
@@ -1812,16 +1811,10 @@ def test_getwriter(self):
         self.assertRaises(TypeError, codecs.getwriter)
         self.assertRaises(LookupError, codecs.getwriter, "__spam__")
 
+    @support.run_with_locale('LC_CTYPE', 'tr_TR')
     def test_lookup_issue1813(self):
         # Issue #1813: under Turkish locales, lookup of some codecs failed
         # because 'I' is lowercased as "ı" (dotless i)
-        oldlocale = locale.setlocale(locale.LC_CTYPE)
-        self.addCleanup(locale.setlocale, locale.LC_CTYPE, oldlocale)
-        try:
-            locale.setlocale(locale.LC_CTYPE, 'tr_TR')
-        except locale.Error:
-            # Unsupported locale on this system
-            self.skipTest('test needs Turkish locale')
         c = codecs.lookup('ASCII')
         self.assertEqual(c.name, 'ascii')
 

Lib/test/test_decimal.py

@@ -1253,7 +1253,7 @@ def test_deprecated_N_format(self):
             self.assertRaises(ValueError, format, h, '10Nf')
             self.assertRaises(ValueError, format, h, 'Nx')
 
-    @run_with_locale('LC_ALL', 'ps_AF')
+    @run_with_locale('LC_ALL', 'ps_AF', '')
     def test_wide_char_separator_decimal_point(self):
         # locale with wide char separator and decimal point
         Decimal = self.decimal.Decimal

Lib/test/test_float.py

@@ -175,7 +175,7 @@ def check(s):
         # non-UTF-8 byte string
         check(b'123\xa0')
 
-    @support.run_with_locale('LC_NUMERIC', 'fr_FR', 'de_DE')
+    @support.run_with_locale('LC_NUMERIC', 'fr_FR', 'de_DE', '')
     def test_float_with_comma(self):
         # set locale to something that doesn't use '.' for the decimal point
         # float must not accept the locale specific decimal point but

Lib/test/test_imaplib.py

@@ -57,7 +57,7 @@ def timevalues(self):
                                        timezone(timedelta(0, 2 * 60 * 60))),
                 '"18-May-2033 05:33:20 +0200"']
 
-    @run_with_locale('LC_ALL', 'de_DE', 'fr_FR')
+    @run_with_locale('LC_ALL', 'de_DE', 'fr_FR', '')
     # DST rules included to work around quirk where the Gnu C library may not
     # otherwise restore the previous time zone
     @run_with_tz('STD-1DST,M3.2.0,M11.1.0')

Lib/test/test_str.py

@@ -1665,7 +1665,7 @@ def test_startswith_endswith_errors(self):
             self.assertIn('str', exc)
             self.assertIn('tuple', exc)
 
-    @support.run_with_locale('LC_ALL', 'de_DE', 'fr_FR')
+    @support.run_with_locale('LC_ALL', 'de_DE', 'fr_FR', '')
     def test_format_float(self):
         # should not format with a comma, but always with C locale
         self.assertEqual('1.0', '%.1f' % 1.0)