Add typed attribute to third party class.

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Issue 类型
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技术栈
flask, python
领域
tooling

调研方向

首先，在 airflow/www/views.py:850 复现 reveal_type 的结果，以及第 115 行附近的 TYPE_CHECKING 尝试。检查 Flask's flask.globals 的类型和 stubgen 如何处理第三方属性。完成标准是：该 issue 具有一种有文档记录且可维护的方法，或具有一个范围明确的 type-checker 功能，可以在不提供完整替代 stub 的情况下为此类属性添加类型。

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描述

feature

Feature

I would like to be able to add a (typed) attribute to a third-party class instance.

To give a specific example, Flask's current_app, and Flask-AppBuilder. Some example code:

    def my_view(self):
        reveal_type(current_app.appbuilder)
        if current_app.appbuilder.sm.has_access(...):
            ...

The reveal_type here shows Any: airflow/www/views.py:850: note: Revealed type is 'Any'

Things I tried:

  1. To add a typed attribute myself:

    if TYPE_CHECKING:
    current_app.appbuilder = AppBuilder(None)
    reveal_type(current_app.appbuilder)

    Didn't work: airflow/www/views.py:115: note: Revealed type is 'Any'

  2. A partial type stub file

    I could use stubgen etc to create a stub file for all of flask and then edit the type in flask.globals, but this presents a maintenance burden that I don't want (keeping it in sync).

    I searched for any way I could to have a "partial" stub file -- if I could have a stubs/flask/globals.pyi with out neededing all the rest of the type stubs for this module, but couldn't get it working - likely not supported.

Pitch

I don't know what the feature would look like, but for the flask ecosystem it is fairly common to add properties on to the global flask object, or the g global variable, and I would love to be able to type-check my use of them, without needing to cast it at each use.

This issue is mostly a request for help/ "is there any sensible way of doing this?"

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