为什么命名数据类字段“date”会导致 RecursionError？

Question

from datetime import date
import dataclasses

@dataclasses.dataclass(frozen=True)
class A:
  date: date = dataclasses.field()

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/Cellar/python/3.7.7/Frameworks/Python.framework/Versions/3.7/lib/python3.7/dataclasses.py", line 1002, in wrap
    return _process_class(cls, init, repr, eq, order, unsafe_hash, frozen)
  File "/usr/local/Cellar/python/3.7.7/Frameworks/Python.framework/Versions/3.7/lib/python3.7/dataclasses.py", line 979, in _process_class
    str(inspect.signature(cls)).replace(' -> None', ''))
  File "/usr/local/Cellar/python/3.7.7/Frameworks/Python.framework/Versions/3.7/lib/python3.7/inspect.py", line 3040, in __str__
    formatted = str(param)
  File "/usr/local/Cellar/python/3.7.7/Frameworks/Python.framework/Versions/3.7/lib/python3.7/inspect.py", line 2558, in __str__
    formatannotation(self._annotation))
  File "/usr/local/Cellar/python/3.7.7/Frameworks/Python.framework/Versions/3.7/lib/python3.7/inspect.py", line 1199, in formatannotation
    return repr(annotation)
  File "/usr/local/Cellar/python/3.7.7/Frameworks/Python.framework/Versions/3.7/lib/python3.7/dataclasses.py", line 249, in __repr__
    return ('Field('
  File "/usr/local/Cellar/python/3.7.7/Frameworks/Python.framework/Versions/3.7/lib/python3.7/dataclasses.py", line 249, in __repr__
    return ('Field('
  File "/usr/local/Cellar/python/3.7.7/Frameworks/Python.framework/Versions/3.7/lib/python3.7/dataclasses.py", line 249, in __repr__
    return ('Field('
  [Previous line repeated 491 more times]
RecursionError: maximum recursion depth exceeded

但这行得通：

@dataclasses.dataclass(frozen=True)
class A:
  date: date

这也是：

@dataclasses.dataclass(frozen=True)
class A:
  date_: date = dataclasses.field()

这是错误还是设计使然？

Answer 1

这个：

date: date = dataclasses.field()

不会将 date 注释为 datetime.date。它将 date 注释为 dataclasses.field()，因为注释是在赋值之后求值的。 dataclasses 不希望字段将自身作为其注释，您也不希望这样。

使用类似

的东西

import datetime
import dataclasses

@dataclasses.dataclass(frozen=True)
class A:
  date: datetime.date = dataclasses.field()

为什么命名数据类字段“date”会导致 RecursionError？

Why does naming a dataclass field `date` cause RecursionError?

python

python-3.x

python-dataclasses