Warn if `__exit__` doesn't have the right signature.

未关闭
#4,885 2 条评论 9 个 reaction 已指派 0 人 在 GitHub 查看

还没有人认领这个 Issue。

评估

难度
4/5
预计耗时
3-5 天
新手友好度
38/100
Issue 类型
功能
描述清晰度
描述清楚
活跃度
停滞
技术栈
python
领域
devtools

调研方向

Start by tracing mypy's existing checks for binary operators and its handling of the ContextManager protocol. Compare those entry points with the standard exit signature shown in the issue; done means incompatible exit methods produce a warning without rejecting compatible implementations.

由索引模型根据 Issue 内容生成。

描述

feature needs discussion priority-2-low

A typeshed user found that zipfile.ZipFile wasn't compatible with the ContextManager protocol, and it turns out that this was because its __exit__ method was declared as taking Exception instead of BaseException: python/typeshed#2043.

I imagine this kind of mistake is pretty common in user code, and it won't be noticed until somebody tries to pass the object to an API that accepts a ContextManager and the user gets an obscure error. Perhaps mypy should warn for __exit__ methods that are not compatible with the standard signature:

    def __exit__(self, t: Optional[Type[BaseException]] = ..., value: Optional[BaseException] = ...,
                 traceback: Optional[TracebackType] = ...) -> bool: ...

Doing this makes more sense for __exit__ than for many other special methods because __exit__'s signature is rather more complicated than that of other dunders, so it's easier to make mistakes. mypy already does something similar for binary operators.

主要语言
Python
星标
20.6k
派生
3.3k
平均合并
1 天 18 小时
30 天内合并 PR
54

贡献指南

打开贡献指南

从这里开始

  1. 先读完整个 Issue，再读项目的贡献指南。
  2. 在 Issue 下留言说明你要接手 —— 这能避免两个人做同样的事。
  3. Fork 仓库，在一个分支上完成修改。
  4. 提交 Pull Request，并在描述里引用这个 Issue 编号。

python/mypy 的其他 Issue

查看 python/mypy 的全部 Issue

相似的 Issue

更多 Python Issue

把新 issue 发到你的邮箱

精选适合新手参与的 GitHub issue 摘要。