Distinguish unnamed timezone file contents in equality

docs/docs/timezones.md

@@ -9,6 +9,13 @@ tries to provide an easy and accurate system to handle them properly.
     can also be used with the standard ``datetime`` library with a few limitations.
     See [Using the timezone library directly](#using-the-timezone-library-directly).
 
+## Timezone equality
+
+Named timezones compare equal when their names match. When the local timezone is
+loaded from a file without a name, equality instead compares the timezone file
+contents. This keeps different unnamed timezones distinct in sets and dictionary
+keys, while preserving equality after pickling and unpickling the same timezone.
+
 ## Normalization
 
 When you create a `DateTime` instance, the library will normalize it for the

src/pendulum/tz/timezone.py

@@ -99,9 +99,15 @@ def _from_pickled_file(cls, data: bytes, key: str | None) -> Self:
         return cls.from_file(io.BytesIO(data), key=key)
 
     def __eq__(self, other: object) -> bool:
-        return isinstance(other, Timezone) and self.key == other.key
+        if not isinstance(other, Timezone) or self.key != other.key:
+            return False
+
+        return self.key is not None or self._file_bytes == other._file_bytes
 
     def __hash__(self) -> int:
+        if self.key is None:
+            return hash((Timezone, self.key, self._file_bytes))
+
         return hash((Timezone, self.key))
 
     @property

tests/tz/test_timezone.py

@@ -5,6 +5,7 @@
 
 from datetime import datetime
 from datetime import timedelta
+from io import BytesIO
 
 import pytest
 
@@ -15,6 +16,7 @@
 from pendulum.tz.exceptions import AmbiguousTime
 from pendulum.tz.exceptions import NonExistingTime
 from pendulum.tz.timezone import FixedTimezone
+from pendulum.tz.timezone import Timezone
 from tests.conftest import assert_datetime
 
 
@@ -479,20 +481,18 @@ def test_repr():
     assert repr(tz) == "Timezone('Europe/Paris')"
 
 
-def _paris_tzif_bytes() -> bytes:
+def _tzif_bytes(name: str) -> bytes:
     # tzdata works the same on every platform pendulum supports, unlike /usr/share/zoneinfo.
     from importlib import resources
 
-    return resources.files("tzdata.zoneinfo").joinpath("Europe", "Paris").read_bytes()
+    return resources.files("tzdata.zoneinfo").joinpath(*name.split("/")).read_bytes()
 
 
 def test_from_file_without_a_key_can_be_pickled():
     # get_local_timezone()'s last-resort fallback builds a Timezone this same way, with no key.
-    from io import BytesIO
-
     import pendulum.tz.timezone as timezone_module
 
-    tz = timezone_module.Timezone.from_file(BytesIO(_paris_tzif_bytes()))
+    tz = timezone_module.Timezone.from_file(BytesIO(_tzif_bytes("Europe/Paris")))
 
     assert tz.key is None
 
@@ -503,3 +503,76 @@ def test_from_file_without_a_key_can_be_pickled():
     assert dt.utcoffset() == timedelta(hours=2)  # CEST, matches Europe/Paris in July
     dt = datetime(2024, 1, 1, 12, tzinfo=unpickled)
     assert dt.utcoffset() == timedelta(hours=1)  # CET, matches Europe/Paris in January
+
+
+@pytest.mark.parametrize("name", ["UTC", "America/New_York", "Europe/London"])
+def test_from_file_without_a_key_distinguishes_zones(name):
+    paris = Timezone.from_file(BytesIO(_tzif_bytes("Europe/Paris")))
+    other = Timezone.from_file(BytesIO(_tzif_bytes(name)))
+
+    assert paris.key is None
+    assert other.key is None
+    assert paris.utcoffset(datetime(2024, 7, 1)) != other.utcoffset(
+        datetime(2024, 7, 1)
+    )
+    assert paris != other
+    assert other != paris
+    assert len({paris, other}) == 2
+    zones = {paris: "Paris", other: name}
+    assert zones[paris] == "Paris"
+    assert zones[other] == name
+
+
+def test_from_file_without_a_key_compares_file_contents():
+    data = _tzif_bytes("Europe/Paris")
+    first = Timezone.from_file(BytesIO(data))
+    second = Timezone.from_file(BytesIO(data))
+
+    assert first is not second
+    assert first == second
+    assert hash(first) == hash(second)
+    assert len({first, second}) == 1
+    assert {first: "Paris"}[second] == "Paris"
+
+
+@pytest.mark.parametrize("protocol", range(pickle.HIGHEST_PROTOCOL + 1))
+def test_from_file_without_a_key_preserves_equality_when_pickled(protocol):
+    original = Timezone.from_file(BytesIO(_tzif_bytes("Europe/Paris")))
+    restored = pickle.loads(pickle.dumps(original, protocol=protocol))
+
+    assert original is not restored
+    assert original == restored
+    assert hash(original) == hash(restored)
+    assert {original: "Paris"}[restored] == "Paris"
+
+
+def test_from_file_named_equality_uses_the_key():
+    data = _tzif_bytes("Europe/Paris")
+    named = Timezone.from_file(BytesIO(data), key="Europe/Paris")
+    uncached = Timezone.no_cache("Europe/Paris")
+    unnamed = Timezone.from_file(BytesIO(data))
+
+    assert named == uncached
+    assert hash(named) == hash(uncached)
+    assert named == Timezone.from_file(BytesIO(_tzif_bytes("UTC")), key="Europe/Paris")
+    assert named != unnamed
+    assert unnamed != named
+    assert named != Timezone.from_file(BytesIO(data), key="custom")
+    assert unnamed != object()
+
+
+def test_local_timezone_files_remain_distinct(tmp_path, monkeypatch):
+    from pendulum.tz.local_timezone import _get_unix_timezone
+
+    monkeypatch.delenv("TZ", raising=False)
+    localtime = tmp_path / "etc" / "localtime"
+    localtime.parent.mkdir()
+    localtime.write_bytes(_tzif_bytes("Europe/Paris"))
+    paris = _get_unix_timezone(_root=str(tmp_path))
+    localtime.write_bytes(_tzif_bytes("UTC"))
+    utc = _get_unix_timezone(_root=str(tmp_path))
+
+    assert paris.key is None
+    assert utc.key is None
+    assert paris != utc
+    assert len({paris, utc}) == 2