我可以在包装函数之前修补Python装饰器吗? [英] Can I patch a Python decorator before it wraps a function?
问题描述
我有一个带有装饰器的函数，正在尝试借助Python 模拟库.我想用mock.patch替换真正的装饰器，使其仅使用模拟的旁路"装饰器，从而调用该函数.
I have a function with a decorator that I'm trying test with the help of the Python Mock library. I'd like to use mock.patch to replace the real decorator with a mock 'bypass' decorator which just calls the function.
我不知道的是如何在真正的装饰器包装功能之前应用补丁.我在补丁程序目标上尝试了几种不同的变体，并对补丁程序和导入语句重新排序，但均未成功.有什么想法吗?
What I can't figure out is how to apply the patch before the real decorator wraps the function. I've tried a few different variations on the patch target and reordering the patch and import statements, but without success. Any ideas?
推荐答案
装饰符在函数定义时应用.对于大多数功能，这是模块加载时的时间. (在其他函数中定义的函数会在每次调用封闭函数时应用装饰器.)
Decorators are applied at function definition time. For most functions, this is when the module is loaded. (Functions that are defined in other functions have the decorator applied each time the enclosing function is called.)
因此，如果您想用猴子修补装饰器，您需要做的是:
So if you want to monkey-patch a decorator, what you need to do is:
- 导入包含它的模块
- 定义模拟装饰器功能
- 设置例如
module.decorator = mymockdecorator - 导入使用装饰器的模块，或在您自己的模块中使用
- Import the module that contains it
- Define the mock decorator function
- Set e.g.
module.decorator = mymockdecorator - Import the module(s) that use the decorator, or use it in your own module
如果包含装饰器的模块也包含使用该装饰器的函数，则在您看到它们时这些装饰已经被装饰，并且您可能是S.O.L.
If the module that contains the decorator also contains functions that use it, those are already decorated by the time you can see them, and you're probably S.O.L.
编辑以反映对Python的更改，因为我最初是这样写的:如果装饰器使用functools.wraps()并且Python版本足够新，则可以使用__wrapped__属性挖掘出原始函数，然后重新装饰它，但这绝不能保证，您要替换的装饰器也可能不是唯一应用的装饰器.
Edit to reflect changes to Python since I originally wrote this: If the decorator uses functools.wraps() and the version of Python is new enough, you may be able to dig out the original function using the __wrapped__ attribute and re-decorate it, but this is by no means guaranteed, and the decorator you want to replace also may not be the only decorator applied.
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