如何覆盖具有 Literal 类型参数的方法？答案

【问题标题】：How to override a method that has an argument of type Literal?如何覆盖具有 Literal 类型参数的方法？
【发布时间】：2022-08-05 12:39:11
【问题描述】：

当我尝试覆盖一个以Literal 作为其类型提示的参数的方法时，我从overrides 模块中得到一个RecursionError（参见下面的堆栈跟踪）。我不确定为什么会发生这种情况，或者是否可以覆盖这些方法。

编辑：我正在谈论的overrides 模块是这个第三方模块：github.com/mkorpela/overrides

这是一个重现我的错误的玩具示例：

from typing import Literal

from overrides import overrides


class Base:
    def foo(self, mode: Literal[\"train\"]) -> None:
        raise NotImplementedError()


class Child(Base):
    @overrides
    def foo(self, mode: Literal[\"train\"]) -> None:
        pass

删除 @overrides 装饰器是一种解决方法，因为它不会改变我的代码的行为，但如果可能的话，我更愿意保留它。我的计划是将 arg 类型更改为 Enum，这可能是一个更好的设计决策。但我很好奇为什么@overrides 和Literal 的这种组合不起作用。

这是堆栈跟踪：

Traceback (most recent call last):
  File \"model-autotraining/temp.py\", line 12, in <module>
    class ChildModel(BaseClass):
  File \"model-autotraining/temp.py\", line 14, in ChildModel
    def foo(self, mode: Literal[\"train\"]) -> None:
  File \"/opt/homebrew/Caskroom/miniforge/base/envs/worker/lib/python3.8/site-packages/overrides/overrides.py\", line 88, in overrides
    return _overrides(method, check_signature, check_at_runtime)
  File \"/opt/homebrew/Caskroom/miniforge/base/envs/worker/lib/python3.8/site-packages/overrides/overrides.py\", line 114, in _overrides
    _validate_method(method, super_class, check_signature)
  File \"/opt/homebrew/Caskroom/miniforge/base/envs/worker/lib/python3.8/site-packages/overrides/overrides.py\", line 135, in _validate_method
    ensure_signature_is_compatible(super_method, method, is_static)
  File \"/opt/homebrew/Caskroom/miniforge/base/envs/worker/lib/python3.8/site-packages/overrides/signature.py\", line 94, in ensure_signature_is_compatible
    ensure_all_kwargs_defined_in_sub(
  File \"/opt/homebrew/Caskroom/miniforge/base/envs/worker/lib/python3.8/site-packages/overrides/signature.py\", line 153, in ensure_all_kwargs_defined_in_sub
    and not _issubtype(super_type_hints[name], sub_type_hints[name])
  File \"/opt/homebrew/Caskroom/miniforge/base/envs/worker/lib/python3.8/site-packages/overrides/signature.py\", line 42, in _issubtype
    return issubtype(left, right)
  File \"/opt/homebrew/Caskroom/miniforge/base/envs/worker/lib/python3.8/site-packages/typing_utils/__init__.py\", line 428, in issubtype
    return _is_normal_subtype(normalize(left), normalize(right), forward_refs)
  File \"/opt/homebrew/Caskroom/miniforge/base/envs/worker/lib/python3.8/site-packages/typing_utils/__init__.py\", line 251, in normalize
    args = _normalize_args(args)
  File \"/opt/homebrew/Caskroom/miniforge/base/envs/worker/lib/python3.8/site-packages/typing_utils/__init__.py\", line 232, in _normalize_args
    return tuple(_normalize_args(type_) for type_ in tps)
  File \"/opt/homebrew/Caskroom/miniforge/base/envs/worker/lib/python3.8/site-packages/typing_utils/__init__.py\", line 232, in <genexpr>
    return tuple(_normalize_args(type_) for type_ in tps)
  File \"/opt/homebrew/Caskroom/miniforge/base/envs/worker/lib/python3.8/site-packages/typing_utils/__init__.py\", line 232, in _normalize_args
    return tuple(_normalize_args(type_) for type_ in tps)
  File \"/opt/homebrew/Caskroom/miniforge/base/envs/worker/lib/python3.8/site-packages/typing_utils/__init__.py\", line 232, in <genexpr>

... repeated many times ...

  File \"/opt/homebrew/Caskroom/miniforge/base/envs/worker/lib/python3.8/site-packages/typing_utils/__init__.py\", line 232, in _normalize_args
    return tuple(_normalize_args(type_) for type_ in tps)
  File \"/opt/homebrew/Caskroom/miniforge/base/envs/worker/lib/python3.8/site-packages/typing_utils/__init__.py\", line 232, in <genexpr>
    return tuple(_normalize_args(type_) for type_ in tps)
  File \"/opt/homebrew/Caskroom/miniforge/base/envs/worker/lib/python3.8/site-packages/typing_utils/__init__.py\", line 231, in _normalize_args
    if isinstance(tps, collections.abc.Sequence):
  File \"/opt/homebrew/Caskroom/miniforge/base/envs/worker/lib/python3.8/abc.py\", line 98, in __instancecheck__
    return _abc_instancecheck(cls, instance)
  File \"/opt/homebrew/Caskroom/miniforge/base/envs/worker/lib/python3.8/abc.py\", line 102, in __subclasscheck__
    return _abc_subclasscheck(cls, subclass)
RecursionError: maximum recursion depth exceeded in comparison

\"来自覆盖模块。\" 这到底是从哪里来的？它does not appear to be a standard library module。这看起来像是该第三方功能中的一个错误，应该这样报告。
没错，它是第三方模块：github.com/mkorpela/overrides。我会将此作为错误报告给他们。我不确定这是否只是一个错误，或者是否有一些更根本的原因此代码不起作用。
已知问题：github.com/mkorpela/overrides/issues/94
那里的讨论说这实际上是typing_utils 中的一个错误。 github.com/bojiang/typing_utils/issues/10。有一个带有修复的 PR，但尚未合并。

标签： python types overriding literals

【解决方案1】：

正如其他人在 cmets 中指出的那样，这种行为是我正在使用的第三方 overrides 模块中的一个错误 https://github.com/mkorpela/overrides)。这是一个已知的错误：https://github.com/mkorpela/overrides/issues/94

【讨论】：

【解决方案2】：

包中的错误现已修复。

【讨论】：