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"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)
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
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)
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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