使用多个装饰器继承装饰器

Question

我使用以下 Mixin 类沿子类继承装饰器。 问题是当一个方法有多个装饰器时，它们不会被识别（只是最后一个）。 例如，如果我有课程：

class Example(InheritDecoratorsMixin): 
  
  @decorator1
  @decorator2
  def method(): 
    pass

然后任何子类都只会继承 decorator1 而不是我想要的 decorator2。 这是 Mixin 类：

class InheritDecoratorsMixin:
  """Mixin Class that allows to inherit decorators.

  Each subclass of this class will have a '_decorator_registry'
  attribute which contains all decorators to be applied.

  Each decorator output must contain the attribute 'inherit_decorator'
  with itself as the value.
  """

  def __init_subclass__(cls, *args, **kwargs):
    super().__init_subclass__(*args, **kwargs)
    decorator_registry = getattr(cls, '_decorator_registry', {}).copy()
    cls._decorator_registry = decorator_registry

    # Check for decorated objects in the mixin itself:
    for name, obj in __class__.__dict__.items():
      if (getattr(obj, 'inherit_decorator', False)
              and name not in decorator_registry):
        decorator_registry[name] = obj.inherit_decorator

    # annotate newly decorated methods in the current subclass:
    for name, obj in cls.__dict__.items():
      if (getattr(obj, 'inherit_decorator', False)
              and name not in decorator_registry):
        decorator_registry[name] = obj.inherit_decorator

    # finally, decorate all methods annotated in the registry:
    for name, decorator in decorator_registry.items():
      if (name in cls.__dict__ and getattr(
              getattr(cls, name), 'inherit_decorator', None) != decorator):
        setattr(cls, name, decorator(cls.__dict__[name]))

谢谢你的帮助。

对于任何装饰师，我都会这样做：

def decorator(func): 
  def wrapper(*args, **kwargs):

    ...
    
    return result

  wrapper.inherit_decorator = decorator
  return wrapper

Answer 1

您正在尝试做的事情很麻烦，如果您确定这种方法，只需相应地修改您正在做的事情：代码中的“decorator_registry”专门为每个方法名称绑定一个装饰器。 更改您的代码，使注册表中的每个条目都是一个列表，而不是单个对象，并维护该列表，而不是在查找新装饰器时替换装饰器。 此外，你的装饰器，而不是仅仅在“inherit_decorator”方法中用最顶层的装饰器本身标记被装饰的函数，应该在这个属性中维护一个所有底层装饰器的列表。

我没有对此进行测试，因为应该有很多极端情况，但总体思路是：

from copy import copy
from functools import wraps

class InheritDecoratorsMixin:
  """Mixin Class that allows to inherit decorators.

  Each subclass of this class will have a '_decorator_registry'
  attribute which contains all decorators to be applied.

  Each decorator output must contain the attribute 'inherit_decorator'
  with itself as the value.
  """

  def __init_subclass__(cls, *args, **kwargs):
    super().__init_subclass__(*args, **kwargs)
    decorator_registry = getattr(cls, '_decorator_registry', {}).copy()
    cls._decorator_registry = decorator_registry

    for class_obj in (__class__, cls):
        
        for name, obj in class_obj.__dict__.items():
            if getattr(obj, 'inherit_decorator', False):
                new_decorators = [deco for deco  in obj.inherit_decorator if deco.__name__ not in decorator_registry.get(name)]
                decorator_registry.setdefault(name, []).extend(new_decorators)

    # finally, decorate all methods annotated in the registry. 
    # note that this code might apply some decorators more than once.

    for name, decorators in decorator_registry.items():
        if name not in cls.__dict__: 
            continue
        method = getattr(cls, name)
        new_method = None
        for deco in decorators:
            if deco in getattr(method, inherit_decorators, []):
                continue
            new_method = deco(method)
        if new_method:
            setattr(cls, name, new_method)
            
def decorator(func): 
    @wraps(func)  # this call preserves name and other properties from the decorated function
    def wrapper(*args, **kwargs):

        ...
        
        return result
    decorators = copy(getattr(func, "inherit_decorator", []))
    decorators.append(decorator)

    wrapper.inherit_decorator = decorators
    return wrapper