Source code for django.utils.decorators

"Functions that help with dynamically creating decorators for views."

try:
    from contextlib import ContextDecorator
except ImportError:
    ContextDecorator = None

from functools import WRAPPER_ASSIGNMENTS, update_wrapper, wraps

from django.utils import six


class classonlymethod(classmethod):
    def __get__(self, instance, owner):
        if instance is not None:
            raise AttributeError("This method is available only on the class, not on instances.")
        return super(classonlymethod, self).__get__(instance, owner)


[docs]def method_decorator(decorator, name=''): """ Converts a function decorator into a method decorator """ # 'obj' can be a class or a function. If 'obj' is a function at the time it # is passed to _dec, it will eventually be a method of the class it is # defined on. If 'obj' is a class, the 'name' is required to be the name # of the method that will be decorated. def _dec(obj): is_class = isinstance(obj, type) if is_class: if name and hasattr(obj, name): func = getattr(obj, name) if not callable(func): raise TypeError( "Cannot decorate '{0}' as it isn't a callable " "attribute of {1} ({2})".format(name, obj, func) ) else: raise ValueError( "The keyword argument `name` must be the name of a method " "of the decorated class: {0}. Got '{1}' instead".format( obj, name, ) ) else: func = obj def decorate(function): """ Apply a list/tuple of decorators if decorator is one. Decorator functions are applied so that the call order is the same as the order in which they appear in the iterable. """ if hasattr(decorator, '__iter__'): for dec in decorator[::-1]: function = dec(function) return function return decorator(function) def _wrapper(self, *args, **kwargs): @decorate def bound_func(*args2, **kwargs2): return func.__get__(self, type(self))(*args2, **kwargs2) # bound_func has the signature that 'decorator' expects i.e. no # 'self' argument, but it is a closure over self so it can call # 'func' correctly. return bound_func(*args, **kwargs) # In case 'decorator' adds attributes to the function it decorates, we # want to copy those. We don't have access to bound_func in this scope, # but we can cheat by using it on a dummy function. @decorate def dummy(*args, **kwargs): pass update_wrapper(_wrapper, dummy) # Need to preserve any existing attributes of 'func', including the name. update_wrapper(_wrapper, func) if is_class: setattr(obj, name, _wrapper) return obj return _wrapper # Don't worry about making _dec look similar to a list/tuple as it's rather # meaningless. if not hasattr(decorator, '__iter__'): update_wrapper(_dec, decorator, assigned=available_attrs(decorator)) # Change the name to aid debugging. if hasattr(decorator, '__name__'): _dec.__name__ = 'method_decorator(%s)' % decorator.__name__ else: _dec.__name__ = 'method_decorator(%s)' % decorator.__class__.__name__ return _dec
[docs]def decorator_from_middleware_with_args(middleware_class): """ Like decorator_from_middleware, but returns a function that accepts the arguments to be passed to the middleware_class. Use like:: cache_page = decorator_from_middleware_with_args(CacheMiddleware) # ... @cache_page(3600) def my_view(request): # ... """ return make_middleware_decorator(middleware_class)
[docs]def decorator_from_middleware(middleware_class): """ Given a middleware class (not an instance), returns a view decorator. This lets you use middleware functionality on a per-view basis. The middleware is created with no params passed. """ return make_middleware_decorator(middleware_class)()
def available_attrs(fn): """ Return the list of functools-wrappable attributes on a callable. This is required as a workaround for http://bugs.python.org/issue3445 under Python 2. """ if six.PY3: return WRAPPER_ASSIGNMENTS else: return tuple(a for a in WRAPPER_ASSIGNMENTS if hasattr(fn, a)) def make_middleware_decorator(middleware_class): def _make_decorator(*m_args, **m_kwargs): middleware = middleware_class(*m_args, **m_kwargs) def _decorator(view_func): @wraps(view_func, assigned=available_attrs(view_func)) def _wrapped_view(request, *args, **kwargs): if hasattr(middleware, 'process_request'): result = middleware.process_request(request) if result is not None: return result if hasattr(middleware, 'process_view'): result = middleware.process_view(request, view_func, args, kwargs) if result is not None: return result try: response = view_func(request, *args, **kwargs) except Exception as e: if hasattr(middleware, 'process_exception'): result = middleware.process_exception(request, e) if result is not None: return result raise if hasattr(response, 'render') and callable(response.render): if hasattr(middleware, 'process_template_response'): response = middleware.process_template_response(request, response) # Defer running of process_response until after the template # has been rendered: if hasattr(middleware, 'process_response'): callback = lambda response: middleware.process_response(request, response) response.add_post_render_callback(callback) else: if hasattr(middleware, 'process_response'): return middleware.process_response(request, response) return response return _wrapped_view return _decorator return _make_decorator if ContextDecorator is None: # ContextDecorator was introduced in Python 3.2 # See https://docs.python.org/3/library/contextlib.html#contextlib.ContextDecorator class ContextDecorator(object): """ A base class that enables a context manager to also be used as a decorator. """ def __call__(self, func): @wraps(func, assigned=available_attrs(func)) def inner(*args, **kwargs): with self: return func(*args, **kwargs) return inner class classproperty(object): def __init__(self, method=None): self.fget = method def __get__(self, instance, owner): return self.fget(owner) def getter(self, method): self.fget = method return self
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