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Source code for django.utils.decorators

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

    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): """ Converts a function decorator into a method decorator """ # 'func' is a function at the time it is passed to _dec, but will eventually # be a method of the class it is defined on. def _dec(func): def _wrapper(self, *args, **kwargs): @decorator 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. @decorator def dummy(*args, **kwargs): pass update_wrapper(_wrapper, dummy) # Need to preserve any existing attributes of 'func', including the name. update_wrapper(_wrapper, func) return _wrapper 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
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