让mypy警告具有不同类型的变量的相等性检查

编辑: 下面我的原始答案描述了如何通过编写自定义mypy插件来实现这一点。

然而, as of mypy 0.700 ,现在可以通过 --strict-equality --strict 旗帜。

例如,在上面的原始程序上运行mypy将产生以下错误:

test.py:4: error: Non-overlapping equality check (left operand type: "int", right operand type: "str")

您可以在页面底部找到有关此标志的更多详细信息 Miscellaneous strictness options mypy命令行标志doc的部分。

这是可能的使用(目前实验和未记录)插件API。

简而言之,在项目中的某个位置添加以下文件:

from typing import Callable, Optional, Type
from mypy.plugin import MethodContext, Plugin
from mypy.meet import is_overlapping_types

class StrictEqualityPlugin(Plugin):
    def get_method_hook(self, fullname: str) -> Optional[Callable[[MethodContext], Type]]:
        if fullname.endswith('__eq__') or fullname.endswith('__ne__'):
            return strict_check_callback

def strict_check_callback(ctx: MethodContext) -> Type:
    if len(ctx.arg_types) == 1 and len(ctx.arg_types[0]) == 1:
        # Note: Expressions of the form 'base_type == arg_type' get
        # translated into `base_type.__eq__(arg_type)`.
        base_type = ctx.type
        arg_type = ctx.arg_types[0][0]

        # Two types are overlapping if one of the types could potentially be the
        # same as or a subtype of the other.
        #
        # If you want something even stricter, add `from mypy.sametypes import is_same_type`
        # up at the top and call `is_same_type` instead of `is_overlapping_types`.
        if not is_overlapping_types(base_type, arg_type):
            ctx.api.msg.warn(
                "The left and right operands have disjoint types ({} and {})".format(
                    ctx.api.msg.format(base_type),
                    ctx.api.msg.format(arg_type),
                ), 
                ctx.context)
    return ctx.default_return_type

def plugin(mypy_version: str) -> Plugin:
    return StrictEqualityPlugin

strict_equality_plugins.py .

然后,在项目的顶层中,创建一个 mypy.ini

[mypy]
plugins = ./path/to/strict_equality_plugins.py

然后,在根项目中运行mypy将产生如下错误:

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