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.

10 files changed, 200 insertions, 85 deletions

diff --git a/Lib/test/pickletester.py b/Lib/test/pickletester.py
index 1722cc8612c..8ef8fae44f1 100644
--- a/Lib/test/pickletester.py
+++ b/Lib/test/pickletester.py
@@ -26,7 +26,7 @@ except ImportError:
 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 @@ class AbstractPickleTests:
                 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.')
diff --git a/Lib/test/support/__init__.py b/Lib/test/support/__init__.py
index 1a44cc638b5..72ce5dacd1b 100644
--- a/Lib/test/support/__init__.py
+++ b/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):
@@ -942,16 +942,21 @@ 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
@@ -960,6 +965,46 @@ def run_with_locale(catstr, *locales):
             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.
 
diff --git a/Lib/test/test_codecs.py b/Lib/test/test_codecs.py
index 428036e1765..290656f0705 100644
--- a/Lib/test/test_codecs.py
+++ b/Lib/test/test_codecs.py
@@ -2,7 +2,6 @@ import codecs
 import contextlib
 import copy
 import io
-import locale
 import pickle
 import sys
 import unittest
@@ -1812,16 +1811,10 @@ class CodecsModuleTest(unittest.TestCase):
         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')
 
diff --git a/Lib/test/test_decimal.py b/Lib/test/test_decimal.py
index c591fd54430..d1e7e69e7e9 100644
--- a/Lib/test/test_decimal.py
+++ b/Lib/test/test_decimal.py
@@ -1253,7 +1253,7 @@ class FormatTest:
             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
diff --git a/Lib/test/test_float.py b/Lib/test/test_float.py
index 048bb145090..f588e16b701 100644
--- a/Lib/test/test_float.py
+++ b/Lib/test/test_float.py
@@ -175,7 +175,7 @@ class GeneralFloatCases(unittest.TestCase):
         # 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
diff --git a/Lib/test/test_imaplib.py b/Lib/test/test_imaplib.py
index 1fd75d0a3f4..a6509fc3ba0 100644
--- a/Lib/test/test_imaplib.py
+++ b/Lib/test/test_imaplib.py
@@ -57,7 +57,7 @@ class TestImaplib(unittest.TestCase):
                                        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')
diff --git a/Lib/test/test_str.py b/Lib/test/test_str.py
index 6600dcf9157..4de6c1cba15 100644
--- a/Lib/test/test_str.py
+++ b/Lib/test/test_str.py
@@ -1665,7 +1665,7 @@ class StrTest(string_tests.StringLikeTest,
             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)
diff --git a/Lib/test/test_strptime.py b/Lib/test/test_strptime.py
index 038746e26c2..37f6b08db28 100644
--- a/Lib/test/test_strptime.py
+++ b/Lib/test/test_strptime.py
@@ -7,7 +7,8 @@ import re
 import os
 import sys
 from test import support
-from test.support import skip_if_buggy_ucrt_strfptime, warnings_helper
+from test.support import warnings_helper
+from test.support import skip_if_buggy_ucrt_strfptime, run_with_locales
 from datetime import date as datetime_date
 
 import _strptime
@@ -207,8 +208,8 @@ class StrptimeTests(unittest.TestCase):
     """Tests for _strptime.strptime."""
 
     def setUp(self):
-        """Create testing time tuple."""
-        self.time_tuple = time.gmtime()
+        """Create testing time tuples."""
+        self.time_tuple = time.localtime()
 
     def test_ValueError(self):
         # Make sure ValueError is raised when match fails or format is bad
@@ -289,54 +290,67 @@ class StrptimeTests(unittest.TestCase):
         # Check ValueError is raised when there is unconverted data
         self.assertRaises(ValueError, _strptime._strptime_time, "10 12", "%m")
 
-    def helper(self, directive, position):
+    def roundtrip(self, fmt, position, time_tuple=None):
         """Helper fxn in testing."""
-        fmt = "%d %Y" if directive == 'd' else "%" + directive
-        strf_output = time.strftime(fmt, self.time_tuple)
+        if time_tuple is None:
+            time_tuple = self.time_tuple
+        strf_output = time.strftime(fmt, time_tuple)
         strp_output = _strptime._strptime_time(strf_output, fmt)
-        self.assertTrue(strp_output[position] == self.time_tuple[position],
-                        "testing of '%s' directive failed; '%s' -> %s != %s" %
-                         (directive, strf_output, strp_output[position],
-                          self.time_tuple[position]))
+        self.assertEqual(strp_output[position], time_tuple[position],
+                        "testing of %r format failed; %r -> %r != %r" %
+                         (fmt, strf_output, strp_output[position],
+                          time_tuple[position]))
+        if support.verbose >= 3:
+            print("testing of %r format: %r -> %r" %
+                  (fmt, strf_output, strp_output[position]))
 
     def test_year(self):
         # Test that the year is handled properly
-        for directive in ('y', 'Y'):
-            self.helper(directive, 0)
+        self.roundtrip('%Y', 0)
+        self.roundtrip('%y', 0)
+        self.roundtrip('%Y', 0, (1900, 1, 1, 0, 0, 0, 0, 1, 0))
+
         # Must also make sure %y values are correct for bounds set by Open Group
-        for century, bounds in ((1900, ('69', '99')), (2000, ('00', '68'))):
-            for bound in bounds:
-                strp_output = _strptime._strptime_time(bound, '%y')
-                expected_result = century + int(bound)
-                self.assertTrue(strp_output[0] == expected_result,
-                                "'y' test failed; passed in '%s' "
-                                "and returned '%s'" % (bound, strp_output[0]))
+        strptime = _strptime._strptime_time
+        self.assertEqual(strptime('00', '%y')[0], 2000)
+        self.assertEqual(strptime('68', '%y')[0], 2068)
+        self.assertEqual(strptime('69', '%y')[0], 1969)
+        self.assertEqual(strptime('99', '%y')[0], 1999)
 
     def test_month(self):
         # Test for month directives
-        for directive in ('B', 'b', 'm'):
-            self.helper(directive, 1)
+        self.roundtrip('%m', 1)
+
+    @run_with_locales('LC_TIME', 'C', 'en_US', 'fr_FR', 'de_DE', 'ja_JP', 'he_IL', '')
+    def test_month_locale(self):
+        # Test for month directives
+        self.roundtrip('%B', 1)
+        self.roundtrip('%b', 1)
+        for m in range(1, 13):
+            self.roundtrip('%B', 1, (1900, m, 1, 0, 0, 0, 0, 1, 0))
+            self.roundtrip('%b', 1, (1900, m, 1, 0, 0, 0, 0, 1, 0))
 
     def test_day(self):
         # Test for day directives
-        self.helper('d', 2)
+        self.roundtrip('%d %Y', 2)
 
     def test_hour(self):
         # Test hour directives
-        self.helper('H', 3)
-        strf_output = time.strftime("%I %p", self.time_tuple)
-        strp_output = _strptime._strptime_time(strf_output, "%I %p")
-        self.assertTrue(strp_output[3] == self.time_tuple[3],
-                        "testing of '%%I %%p' directive failed; '%s' -> %s != %s" %
-                         (strf_output, strp_output[3], self.time_tuple[3]))
+        self.roundtrip('%H', 3)
+
+    # NB: Only works on locales with AM/PM
+    @run_with_locales('LC_TIME', 'C', 'en_US', 'ja_JP')
+    def test_hour_locale(self):
+        # Test hour directives
+        self.roundtrip('%I %p', 3)
 
     def test_minute(self):
         # Test minute directives
-        self.helper('M', 4)
+        self.roundtrip('%M', 4)
 
     def test_second(self):
         # Test second directives
-        self.helper('S', 5)
+        self.roundtrip('%S', 5)
 
     def test_fraction(self):
         # Test microseconds
@@ -347,12 +361,18 @@ class StrptimeTests(unittest.TestCase):
 
     def test_weekday(self):
         # Test weekday directives
-        for directive in ('A', 'a', 'w', 'u'):
-            self.helper(directive,6)
+        self.roundtrip('%w', 6)
+        self.roundtrip('%u', 6)
+
+    @run_with_locales('LC_TIME', 'C', 'en_US', 'fr_FR', 'de_DE', 'ja_JP', '')
+    def test_weekday_locale(self):
+        # Test weekday directives
+        self.roundtrip('%A', 6)
+        self.roundtrip('%a', 6)
 
     def test_julian(self):
         # Test julian directives
-        self.helper('j', 7)
+        self.roundtrip('%j', 7)
 
     def test_offset(self):
         one_hour = 60 * 60
@@ -449,20 +469,96 @@ class StrptimeTests(unittest.TestCase):
                     "time.daylight set to %s and passing in %s" %
                     (time.tzname, tz_value, time.daylight, tz_name))
 
-    def test_date_time(self):
+    # NB: Does not roundtrip in some locales due to the ambiguity of
+    # the date and time representation (bugs in locales?):
+    # * Seconds are not included: bem_ZM, bokmal, ff_SN, nb_NO, nn_NO,
+    #   no_NO, norwegian, nynorsk.
+    # * Hours are in 12-hour notation without AM/PM indication: hy_AM,
+    #   id_ID, ms_MY.
+    # * Year is not included: ha_NG.
+    # * Use non-Gregorian calendar: lo_LA, thai, th_TH.
+    #
+    # BUG: Generates invalid regexp for br_FR, csb_PL, Arabic.
+    # BUG: Generates regexp that does not match the current date and time
+    # for fa_IR, gez_ER, gez_ET, lzh_TW, my_MM, or_IN, shn_MM, yo_NG.
+    # BUG: Generates regexp that does not match the current date and time
+    # for fa_IR, gez_ER, gez_ET, lzh_TW, my_MM, or_IN, shn_MM, yo_NG,
+    # fr_FR, ja_JP, he_IL, ko_KR, zh_CN, etc.
+    @run_with_locales('LC_TIME', 'C', 'en_US', 'de_DE',
+                      'eu_ES', 'mfe_MU')
+    def test_date_time_locale(self):
         # Test %c directive
-        for position in range(6):
-            self.helper('c', position)
-
-    def test_date(self):
+        now = time.time()
+        self.roundtrip('%c', slice(0, 6), time.localtime(now))
+        # 1 hour 20 minutes 30 seconds ago
+        self.roundtrip('%c', slice(0, 6), time.localtime(now - 4830))
+        # 12 hours ago
+        self.roundtrip('%c', slice(0, 6), time.localtime(now - 12*3600))
+        # different days of the week
+        for i in range(1, 7):
+            self.roundtrip('%c', slice(0, 6), time.localtime(now - i*24*3600))
+        # different months
+        for i in range(1, 12):
+            self.roundtrip('%c', slice(0, 6), time.localtime(now - i*30*24*3600))
+        # different year
+        self.roundtrip('%c', slice(0, 6), time.localtime(now - 366*24*3600))
+
+    # NB: Dates before 1969 do not roundtrip on some locales:
+    # bo_CN, bo_IN, dz_BT, eu_ES, eu_FR.
+    @run_with_locales('LC_TIME', 'C', 'en_US', 'de_DE', 'ja_JP')
+    def test_date_time_locale2(self):
+        # Test %c directive
+        self.roundtrip('%c', slice(0, 6), (1900, 1, 1, 0, 0, 0, 0, 1, 0))
+
+    # NB: Does not roundtrip because use non-Gregorian calendar:
+    # lo_LA, thai, th_TH.
+    # BUG: Generates regexp that does not match the current date
+    # for az_IR, fa_IR, lzh_TW, my_MM, or_IN, shn_MM,
+    # Arabic, ja_JP, ko_KR, zh_CN, etc.
+    @run_with_locales('LC_TIME', 'C', 'en_US', 'fr_FR', 'de_DE',
+                      'he_IL', 'eu_ES')
+    def test_date_locale(self):
         # Test %x directive
-        for position in range(0,3):
-            self.helper('x', position)
-
-    def test_time(self):
+        now = time.time()
+        self.roundtrip('%x', slice(0, 3), time.localtime(now))
+        # different days of the week
+        for i in range(1, 7):
+            self.roundtrip('%x', slice(0, 3), time.localtime(now - i*24*3600))
+        # different months
+        for i in range(1, 12):
+            self.roundtrip('%x', slice(0, 3), time.localtime(now - i*30*24*3600))
+        # different year
+        self.roundtrip('%x', slice(0, 3), time.localtime(now - 366*24*3600))
+
+    # NB: Dates before 1969 do not roundtrip on many locales, including C.
+    @unittest.skipIf(
+        support.is_emscripten or support.is_wasi,
+        "musl libc issue on Emscripten, bpo-46390"
+    )
+    @run_with_locales('LC_TIME', 'en_US', 'fr_FR', 'de_DE', 'ja_JP')
+    def test_date_locale2(self):
+        # Test %x directive
+        self.roundtrip('%x', slice(0, 3), (1900, 1, 1, 0, 0, 0, 0, 1, 0))
+
+    # NB: Does not roundtrip in some locales due to the ambiguity of
+    # the time representation (bugs in locales?):
+    # * Seconds are not included: bokmal, ff_SN, nb_NO, nn_NO, no_NO,
+    #   norwegian, nynorsk.
+    # * Hours are in 12-hour notation without AM/PM indication: hy_AM,
+    #   ms_MY, sm_WS.
+    # BUG: Generates regexp that does not match the current time for
+    # aa_DJ, aa_ER, aa_ET, am_ET, az_IR, byn_ER, fa_IR, gez_ER, gez_ET,
+    # lzh_TW, my_MM, om_ET, om_KE, or_IN, shn_MM, sid_ET, so_DJ, so_ET,
+    # so_SO, ti_ER, ti_ET, tig_ER, wal_ET.
+    @run_with_locales('LC_TIME', 'C', 'en_US', 'fr_FR', 'de_DE', 'ja_JP')
+    def test_time_locale(self):
         # Test %X directive
-        for position in range(3,6):
-            self.helper('X', position)
+        now = time.time()
+        self.roundtrip('%X', slice(3, 6), time.localtime(now))
+        # 1 hour 20 minutes 30 seconds ago
+        self.roundtrip('%X', slice(3, 6), time.localtime(now - 4830))
+        # 12 hours ago
+        self.roundtrip('%X', slice(3, 6), time.localtime(now - 12*3600))
 
     def test_percent(self):
         # Make sure % signs are handled properly
@@ -714,12 +810,7 @@ class CacheTests(unittest.TestCase):
 
     def test_TimeRE_recreation_locale(self):
         # The TimeRE instance should be recreated upon changing the locale.
-        locale_info = locale.getlocale(locale.LC_TIME)
-        try:
-            locale.setlocale(locale.LC_TIME, ('en_US', 'UTF8'))
-        except locale.Error:
-            self.skipTest('test needs en_US.UTF8 locale')
-        try:
+        with support.run_with_locale('LC_TIME', 'en_US.UTF8'):
             _strptime._strptime_time('10 2004', '%d %Y')
             # Get id of current cache object.
             first_time_re = _strptime._TimeRE_cache
@@ -736,10 +827,6 @@ class CacheTests(unittest.TestCase):
             # to the resetting to the original locale.
             except locale.Error:
                 self.skipTest('test needs de_DE.UTF8 locale')
-        # Make sure we don't trample on the locale setting once we leave the
-        # test.
-        finally:
-            locale.setlocale(locale.LC_TIME, locale_info)
 
     @support.run_with_tz('STD-1DST,M4.1.0,M10.1.0')
     def test_TimeRE_recreation_timezone(self):
diff --git a/Lib/test/test_time.py b/Lib/test/test_time.py
index 530c317a852..5b5779231f0 100644
--- a/Lib/test/test_time.py
+++ b/Lib/test/test_time.py
@@ -2,7 +2,6 @@ from test import support
 from test.support import warnings_helper
 import decimal
 import enum
-import locale
 import math
 import platform
 import sys
@@ -600,17 +599,8 @@ class TimeTestCase(unittest.TestCase):
 
 
 class TestLocale(unittest.TestCase):
-    def setUp(self):
-        self.oldloc = locale.setlocale(locale.LC_ALL)
-
-    def tearDown(self):
-        locale.setlocale(locale.LC_ALL, self.oldloc)
-
+    @support.run_with_locale('LC_ALL', 'fr_FR', '')
     def test_bug_3061(self):
-        try:
-            tmp = locale.setlocale(locale.LC_ALL, "fr_FR")
-        except locale.Error:
-            self.skipTest('could not set locale.LC_ALL to fr_FR')
         # This should not cause an exception
         time.strftime("%B", (2009,2,1,0,0,0,0,0,0))
 
diff --git a/Lib/test/test_types.py b/Lib/test/test_types.py
index 3c9e33e3c9d..d1161719d98 100644
--- a/Lib/test/test_types.py
+++ b/Lib/test/test_types.py
@@ -398,7 +398,7 @@ class TypesTests(unittest.TestCase):
         test(123456, "1=20", '11111111111111123456')
         test(123456, "*=20", '**************123456')
 
-    @run_with_locale('LC_NUMERIC', 'en_US.UTF8')
+    @run_with_locale('LC_NUMERIC', 'en_US.UTF8', '')
     def test_float__format__locale(self):
         # test locale support for __format__ code 'n'
 
@@ -407,7 +407,7 @@ class TypesTests(unittest.TestCase):
             self.assertEqual(locale.format_string('%g', x, grouping=True), format(x, 'n'))
             self.assertEqual(locale.format_string('%.10g', x, grouping=True), format(x, '.10n'))
 
-    @run_with_locale('LC_NUMERIC', 'en_US.UTF8')
+    @run_with_locale('LC_NUMERIC', 'en_US.UTF8', '')
     def test_int__format__locale(self):
         # test locale support for __format__ code 'n' for integers