Date string coerced to datetime infers timezone #8762
Description
Initial Checks
- I confirm that I'm using Pydantic V2
Description
Split from #8736 (comment)
Coercion of date strings to midnight datetimes, new in v2.6, infers a UTC timezone.
This is inconsistent with coercion of datetime strings to datetimes, which do not infer a timezone; they only add one when explicitly given.
I believe quite strongly that timezone should not be inferred here, and this is a bug in the new date-to-midnight coercion.
Example Code
from pydantic import TypeAdapter
from datetime import datetime
print(repr(TypeAdapter(datetime).validate_python("2021-01-01").tzinfo))
#> TzInfo(UTC) # <-- this should be None to be consistent with the case below
print(repr(TypeAdapter(datetime).validate_python("2021-01-01T00:00:00").tzinfo))
#> None
print(repr(TypeAdapter(datetime).validate_python("2021-01-01T00:00:00Z").tzinfo))
#> TzInfo(UTC)
print(repr(TypeAdapter(datetime).validate_python("2021-01-01T00:00:00+01:00").tzinfo))
#> TzInfo(+01:00)Python, Pydantic & OS Version
pydantic version: 2.6.1
pydantic-core version: 2.16.2
pydantic-core build: profile=release pgo=true
install path: /home/david/.virtualenvs/pydantic-prod/lib/python3.11/site-packages/pydantic
python version: 3.11.6 (main, Oct 8 2023, 05:06:43) [GCC 13.2.0]
platform: Linux-5.15.133.1-microsoft-standard-WSL2-x86_64-with-glibc2.38
related packages: mypy-1.4.1 pydantic-settings-2.1.0 email-validator-2.0.0.post2 pyright-1.1.316 typing_extensions-4.6.3
commit: unknown