Dataclasses fields should evaluate their annotations

Feature or enhancement

Proposal:

In Python 3.14 (a5), I was surprised that while

import dataclasses

@dataclasses.dataclass
class X:
    a: X | None

print(X.__annotations__)

works as expected and prints,

{'a': __main__.X | None}

if one tries to look at the type of the field using the dataclasses.fields interface:

print(dataclasses.fields(X)[0].type)

then this instead results in a ForwardRef

ForwardRef('X | None')

Surely, someone trying to inspect the field would want the value version, consistent with the new default functionality of __annotations__ rather than trying to figure out how to evaluate the ForwardRef precisely.

The current behaviour was introduced in

https://github.com/python/cpython/commit/7b7b90d1ce5116f29ad6c8120c0490824baa54e0#diff-44ce2dc1c4922b2f5cf7631d8f86cc569a4c25eb003aaecdc2bc22eb9163d5f5R986

where the dataclasses fields are constructed by reading the ForwardRef mode of annotationlib.

I believe this would be backwards in that the type value had to exists without from __future__ import annotations and would be a string with it.

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

No response

首先检查所引用的 CPython 提交以及读取 annotationlib 的 ForwardRef 模式的 dataclasses 字段构造。将该行为与 annotations 中的求值结果进行比较，然后确定兼容的 field.type 语义，并根据文档中记录的向后兼容性问题验证所提议的更改。