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DateTime.combine should default to time.tzinfo #20

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Merged
glyph merged 1 commit into from
Nov 12, 2025
Merged

DateTime.combine should default to time.tzinfo #20

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6 changes: 5 additions & 1 deletion src/datetype/__init__.py
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Original file line number Diff line number Diff line change
Expand Up @@ -39,6 +39,8 @@
AnyDateTime = TypeVar("AnyDateTime", bound="DateTime[Optional[_tzinfo]]")
AnyTime = TypeVar("AnyTime", bound="Time[Optional[_tzinfo]]")

_missing = object()

if sys.version_info >= (3, 9):

class _IsoCalendarDate(NamedTuple):
Expand Down Expand Up @@ -513,8 +515,10 @@ def combine(
cls,
date: Date,
time: Time[Optional[_tzinfo]],
tzinfo: Optional[_tzinfo] = None,
tzinfo: Optional[_tzinfo] = _missing, # type: ignore[assignment]
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@RazerM RazerM Nov 11, 2025

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Some context for the sentinel I used here:

The Python implemention of CPython's datetime module uses True for the sentinel, but that is not part of the API and doesn't work with the builtin module:

❯ uv run --isolated --no-project -p 3.14 python
Python 3.14.0 (main, Oct 28 2025, 12:03:45) [Clang 20.1.4 ] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import _datetime
>>> import _pydatetime
>>> _pydatetime.datetime.combine(_pydatetime.date.today(), _pydatetime.time(tzinfo=_pydatetime.UTC), True)
datetime.datetime(2025, 11, 11, 0, 0, tzinfo=datetime.timezone.utc)
>>> _datetime.datetime.combine(_datetime.date.today(), _datetime.time(tzinfo=_datetime.UTC), True)
Traceback (most recent call last):
  File "<python-input-3>", line 1, in <module>
    _datetime.datetime.combine(_datetime.date.today(), _datetime.time(tzinfo=_datetime.UTC), True)
    ~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: tzinfo argument must be None or of a tzinfo subclass, not type 'bool'

) -> DateTime[Optional[_tzinfo]]:
if tzinfo is _missing:
tzinfo = time.tzinfo
return _datetime.combine(
concrete(date), concrete(time), tzinfo
) # type:ignore[return-value]
Expand Down
29 changes: 29 additions & 0 deletions src/datetype/test/test_datetype.py
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Expand Up @@ -12,6 +12,7 @@
aware,
naive,
DateTime,
date_only,
)

TEST_DATA = (Path(__file__) / "..").resolve()
Expand Down Expand Up @@ -109,3 +110,31 @@ def test_differing_zone_subtract(self) -> None:

self.assertEqual(dtzi - dttz, timedelta(0))
self.assertEqual(dttz - dtzi, timedelta(0))

def test_combine(self) -> None:
from zoneinfo import ZoneInfo

d = date_only(date(2025, 2, 13))
aware_time = aware(
time(hour=15, minute=35, second=13, tzinfo=timezone.utc), timezone
)
naive_time = naive(time(hour=15, minute=35, second=13))

combined_aware: DateTime[timezone] = DateTime.combine(d, aware_time)
combined_naive: DateTime[None] = DateTime.combine(d, naive_time)

self.assertIsInstance(combined_naive, NaiveDateTime)
self.assertIsInstance(combined_aware, AwareDateTime)
self.assertIs(combined_aware.tzinfo, timezone.utc)

zi = ZoneInfo("Europe/Berlin")

adt_zi: DateTime[ZoneInfo] = DateTime.combine(d, aware_time, zi)
self.assertIsInstance(adt_zi, AwareDateTime)
adt_naive: DateTime[None] = DateTime.combine(d, aware_time, tzinfo=None)
self.assertIsInstance(adt_naive, NaiveDateTime)

ndt_zi: DateTime[ZoneInfo] = DateTime.combine(d, naive_time, zi)
self.assertIsInstance(ndt_zi, AwareDateTime)
ndt_naive: DateTime[None] = DateTime.combine(d, naive_time, tzinfo=None)
self.assertIsInstance(ndt_naive, NaiveDateTime)