Add property tests for the zoneinfo module

This migrates the tests from
https://github.com/Zac-HD/stdlib-property-tests into the standard
library, using the hypothesis stubs.

Lib/test/test_zoneinfo/__init__.py

@@ -1 +1,2 @@
 from .test_zoneinfo import *
+from .test_zoneinfo_property import *

Lib/test/test_zoneinfo/test_zoneinfo_property.py

@@ -0,0 +1,318 @@
+import contextlib
+import datetime
+import os
+import pickle
+import unittest
+import zoneinfo
+
+from test.support.hypothesis_helper import hypothesis
+
+import test.test_zoneinfo._support as test_support
+
+ZoneInfoTestBase = test_support.ZoneInfoTestBase
+
+py_zoneinfo, c_zoneinfo = test_support.get_modules()
+
+UTC = datetime.timezone.utc
+MIN_UTC = datetime.datetime.min.replace(tzinfo=UTC)
+MAX_UTC = datetime.datetime.max.replace(tzinfo=UTC)
+ZERO = datetime.timedelta(0)
+
+
+def _valid_keys():
+    """Get available time zones, including posix/ and right/ directories."""
+    from importlib import resources
+
+    available_zones = sorted(zoneinfo.available_timezones())
+    TZPATH = zoneinfo.TZPATH
+
+    def valid_key(key):
+        for root in TZPATH:
+            key_file = os.path.join(root, key)
+            if os.path.exists(key_file):
+                return True
+
+        components = key.split("/")
+        package_name = ".".join(["tzdata.zoneinfo"] + components[:-1])
+        resource_name = components[-1]
+
+        try:
+            return resources.files(package_name).joinpath(resource_name).is_file()
+        except ModuleNotFoundError:
+            return False
+
+    # This relies on the fact that dictionaries maintain insertion order — for
+    # shrinking purposes, it is preferable to start with the standard version,
+    # then move to the posix/ version, then to the right/ version.
+    out_zones = {"": available_zones}
+    for prefix in ["posix", "right"]:
+        prefix_out = []
+        for key in available_zones:
+            prefix_key = f"{prefix}/{key}"
+            if valid_key(prefix_key):
+                prefix_out.append(prefix_key)
+
+        out_zones[prefix] = prefix_out
+
+    output = []
+    for keys in out_zones.values():
+        output.extend(keys)
+
+    return output
+
+
+VALID_KEYS = _valid_keys()
+if not VALID_KEYS:
+    raise unittest.SkipTest("No time zone data available")
+
+
+def valid_keys():
+    return hypothesis.strategies.sampled_from(VALID_KEYS)
+
+
+class ZoneInfoTest(ZoneInfoTestBase):
+    module = py_zoneinfo
+
+    @hypothesis.given(key=valid_keys())
+    def test_str(self, key):
+        zi = self.klass(key)
+        self.assertEqual(str(zi), key)
+
+    @hypothesis.given(key=valid_keys())
+    def test_key(self, key):
+        zi = self.klass(key)
+
+        self.assertEqual(zi.key, key)
+
+    @hypothesis.given(
+        dt=hypothesis.strategies.one_of(
+            hypothesis.strategies.datetimes(), hypothesis.strategies.times()
+        )
+    )
+    def test_utc(self, dt):
+        zi = self.klass("UTC")
+        dt_zi = dt.replace(tzinfo=zi)
+
+        self.assertEqual(dt_zi.utcoffset(), ZERO)
+        self.assertEqual(dt_zi.dst(), ZERO)
+        self.assertEqual(dt_zi.tzname(), "UTC")
+
+
+class CZoneInfoTest(ZoneInfoTest):
+    module = c_zoneinfo
+
+
+class ZoneInfoPickleTest(ZoneInfoTestBase):
+    module = py_zoneinfo
+
+    def setUp(self):
+        with contextlib.ExitStack() as stack:
+            stack.enter_context(test_support.set_zoneinfo_module(self.module))
+            self.addCleanup(stack.pop_all().close)
+
+        super().setUp()
+
+    @hypothesis.given(key=valid_keys())
+    def test_pickle_unpickle_cache(self, key):
+        zi = self.klass(key)
+        pkl_str = pickle.dumps(zi)
+        zi_rt = pickle.loads(pkl_str)
+
+        self.assertIs(zi, zi_rt)
+
+    @hypothesis.given(key=valid_keys())
+    def test_pickle_unpickle_no_cache(self, key):
+        zi = self.klass.no_cache(key)
+        pkl_str = pickle.dumps(zi)
+        zi_rt = pickle.loads(pkl_str)
+
+        self.assertIsNot(zi, zi_rt)
+        self.assertEqual(str(zi), str(zi_rt))
+
+    @hypothesis.given(key=valid_keys())
+    def test_pickle_unpickle_cache_multiple_rounds(self, key):
+        """Test that pickle/unpickle is idempotent."""
+        zi_0 = self.klass(key)
+        pkl_str_0 = pickle.dumps(zi_0)
+        zi_1 = pickle.loads(pkl_str_0)
+        pkl_str_1 = pickle.dumps(zi_1)
+        zi_2 = pickle.loads(pkl_str_1)
+        pkl_str_2 = pickle.dumps(zi_2)
+
+        self.assertEqual(pkl_str_0, pkl_str_1)
+        self.assertEqual(pkl_str_1, pkl_str_2)
+
+        self.assertIs(zi_0, zi_1)
+        self.assertIs(zi_0, zi_2)
+        self.assertIs(zi_1, zi_2)
+
+    @hypothesis.given(key=valid_keys())
+    def test_pickle_unpickle_no_cache_multiple_rounds(self, key):
+        """Test that pickle/unpickle is idempotent."""
+        zi_cache = self.klass(key)
+
+        zi_0 = self.klass.no_cache(key)
+        pkl_str_0 = pickle.dumps(zi_0)
+        zi_1 = pickle.loads(pkl_str_0)
+        pkl_str_1 = pickle.dumps(zi_1)
+        zi_2 = pickle.loads(pkl_str_1)
+        pkl_str_2 = pickle.dumps(zi_2)
+
+        self.assertEqual(pkl_str_0, pkl_str_1)
+        self.assertEqual(pkl_str_1, pkl_str_2)
+
+        self.assertIsNot(zi_0, zi_1)
+        self.assertIsNot(zi_0, zi_2)
+        self.assertIsNot(zi_1, zi_2)
+
+        self.assertIsNot(zi_0, zi_cache)
+        self.assertIsNot(zi_1, zi_cache)
+        self.assertIsNot(zi_2, zi_cache)
+
+
+class CZoneInfoPickleTest(ZoneInfoPickleTest):
+    module = c_zoneinfo
+
+
+class ZoneInfoCacheTest(ZoneInfoTestBase):
+    module = py_zoneinfo
+
+    @hypothesis.given(key=valid_keys())
+    def test_cache(self, key):
+        zi_0 = self.klass(key)
+        zi_1 = self.klass(key)
+
+        self.assertIs(zi_0, zi_1)
+
+    @hypothesis.given(key=valid_keys())
+    def test_no_cache(self, key):
+        zi_0 = self.klass.no_cache(key)
+        zi_1 = self.klass.no_cache(key)
+
+        self.assertIsNot(zi_0, zi_1)
+
+
+class CZoneInfoCacheTest(ZoneInfoCacheTest):
+    klass = c_zoneinfo.ZoneInfo
+
+
+class PythonCConsistencyTest(unittest.TestCase):
+    """Tests that the C and Python versions do the same thing."""
+
+    def _is_ambiguous(self, dt):
+        return dt.replace(fold=not dt.fold).utcoffset() == dt.utcoffset()
+
+    @hypothesis.given(dt=hypothesis.strategies.datetimes(), key=valid_keys())
+    def test_same_str(self, dt, key):
+        py_dt = dt.replace(tzinfo=py_zoneinfo.ZoneInfo(key))
+        c_dt = dt.replace(tzinfo=c_zoneinfo.ZoneInfo(key))
+
+        self.assertEqual(str(py_dt), str(c_dt))
+
+    @hypothesis.given(dt=hypothesis.strategies.datetimes(), key=valid_keys())
+    def test_same_offsets_and_names(self, dt, key):
+        py_dt = dt.replace(tzinfo=py_zoneinfo.ZoneInfo(key))
+        c_dt = dt.replace(tzinfo=c_zoneinfo.ZoneInfo(key))
+
+        self.assertEqual(py_dt.tzname(), c_dt.tzname())
+        self.assertEqual(py_dt.utcoffset(), c_dt.utcoffset())
+        self.assertEqual(py_dt.dst(), c_dt.dst())
+
+    @hypothesis.given(
+        dt=hypothesis.strategies.datetimes(timezones=hypothesis.strategies.just(UTC)),
+        key=valid_keys(),
+    )
+    @hypothesis.example(dt=MIN_UTC, key="Asia/Tokyo")
+    @hypothesis.example(dt=MAX_UTC, key="Asia/Tokyo")
+    @hypothesis.example(dt=MIN_UTC, key="America/New_York")
+    @hypothesis.example(dt=MAX_UTC, key="America/New_York")
+    @hypothesis.example(
+        dt=datetime.datetime(2006, 10, 29, 5, 15, tzinfo=UTC),
+        key="America/New_York",
+    )
+    def test_same_from_utc(self, dt, key):
+        py_zi = py_zoneinfo.ZoneInfo(key)
+        c_zi = c_zoneinfo.ZoneInfo(key)
+
+        # Convert to UTC: This can overflow, but we just care about consistency
+        py_overflow_exc = None
+        c_overflow_exc = None
+        try:
+            py_dt = dt.astimezone(py_zi)
+        except OverflowError as e:
+            py_overflow_exc = e
+
+        try:
+            c_dt = dt.astimezone(c_zi)
+        except OverflowError as e:
+            c_overflow_exc = e
+
+        if (py_overflow_exc is not None) != (c_overflow_exc is not None):
+            raise py_overflow_exc or c_overflow_exc  # pragma: nocover
+
+        if py_overflow_exc is not None:
+            return  # Consistently raises the same exception
+
+        # PEP 495 says that an inter-zone comparison between ambiguous
+        # datetimes is always False.
+        if py_dt != c_dt:
+            self.assertEqual(
+                self._is_ambiguous(py_dt),
+                self._is_ambiguous(c_dt),
+                (py_dt, c_dt),
+            )
+
+        self.assertEqual(py_dt.tzname(), c_dt.tzname())
+        self.assertEqual(py_dt.utcoffset(), c_dt.utcoffset())
+        self.assertEqual(py_dt.dst(), c_dt.dst())
+
+    @hypothesis.given(dt=hypothesis.strategies.datetimes(), key=valid_keys())
+    @hypothesis.example(dt=datetime.datetime.max, key="America/New_York")
+    @hypothesis.example(dt=datetime.datetime.min, key="America/New_York")
+    @hypothesis.example(dt=datetime.datetime.min, key="Asia/Tokyo")
+    @hypothesis.example(dt=datetime.datetime.max, key="Asia/Tokyo")
+    def test_same_to_utc(self, dt, key):
+        py_dt = dt.replace(tzinfo=py_zoneinfo.ZoneInfo(key))
+        c_dt = dt.replace(tzinfo=c_zoneinfo.ZoneInfo(key))
+
+        # Convert from UTC: Overflow OK if it happens in both implementations
+        py_overflow_exc = None
+        c_overflow_exc = None
+        try:
+            py_utc = py_dt.astimezone(UTC)
+        except OverflowError as e:
+            py_overflow_exc = e
+
+        try:
+            c_utc = c_dt.astimezone(UTC)
+        except OverflowError as e:
+            c_overflow_exc = e
+
+        if (py_overflow_exc is not None) != (c_overflow_exc is not None):
+            raise py_overflow_exc or c_overflow_exc  # pragma: nocover
+
+        if py_overflow_exc is not None:
+            return  # Consistently raises the same exception
+
+        self.assertEqual(py_utc, c_utc)
+
+    @hypothesis.given(key=valid_keys())
+    def test_cross_module_pickle(self, key):
+        py_zi = py_zoneinfo.ZoneInfo(key)
+        c_zi = c_zoneinfo.ZoneInfo(key)
+
+        with test_support.set_zoneinfo_module(py_zoneinfo):
+            py_pkl = pickle.dumps(py_zi)
+
+        with test_support.set_zoneinfo_module(c_zoneinfo):
+            c_pkl = pickle.dumps(c_zi)
+
+        with test_support.set_zoneinfo_module(c_zoneinfo):
+            # Python → C
+            py_to_c_zi = pickle.loads(py_pkl)
+            self.assertIs(py_to_c_zi, c_zi)
+
+        with test_support.set_zoneinfo_module(py_zoneinfo):
+            # C → Python
+            c_to_py_zi = pickle.loads(c_pkl)
+            self.assertIs(c_to_py_zi, py_zi)