Fix dataclass ignoring default_factory passed in Annotated

[kc0506]

Change Summary

This is a fix for bug reported in #9947. When using pydantic.dataclass with Annotated and Field(default_factory=...), the generated field does not have correct default_factory.

The only change I made was changing

if dc_field.default_factory is dataclasses.MISSING:
    default_factory: typing.Callable[[], Any] | None = None

to

if dc_field.default_factory is dataclasses.MISSING:
    default_factory: typing.Callable[[], Any] | None = _Unset

in FieldInfo._from_dataclass_field function.

The original assignment of None will cause default_factory to be override in FieldInfo.merge_field_infos method, which is called in collect_dataclass_fields.

Related issue number

fix #9947

Checklist

• The pull request title is a good summary of the changes - it will be used in the changelog
• Unit tests for the changes exist
• Tests pass on CI
• Documentation reflects the changes where applicable
• My PR is ready to review, please add a comment including the phrase "please review" to assign reviewers

[codspeed-hq]

CodSpeed Performance Report

Merging #9971 will not alter performance

_{Comparing kc0506:fix-dataclass-field-default-factory (6b3b1fb) with main (d92d341)}

Summary

✅ 14 untouched benchmarks

[AlessandroMiola]

Without entering into the details of the fix, perhaps you might want to call make format to let ruff fix formatting for you...

[kc0506]

I did run the make format command, but weirdly I only got the following output:

PDM, version 2.17.1
pdm run ruff check --fix pydantic tests docs/plugins
All checks passed!
pdm run ruff format pydantic tests docs/plugins
87 files left unchanged

It does not format the unformatted test file, so I have to explicitly format it:

$ pdm run ruff format .\tests\test_dataclasses.pytaclasses.py  test_datetime.py
1 file reformatted                              

It does work for files under pydantic/ though.

[AlessandroMiola]

Interesting 🤔 might be worth a check IMO as pdm run ruff format pydantic tests docs/plugins does consider tests.

[sydney-runkle]

Looks good overall - I had a few follow up requests.

Thanks so much for your contribution!

[sydney-runkle]

Wonderful, thanks for the fix and the amazingly fast turnaround!

[saintx]

Thank you!