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Source code for pyramid.tweens

import sys

from pyramid.interfaces import (
    IExceptionViewClassifier,
    IRequest,
    IView,
    )

from zope.interface import providedBy

[docs]def excview_tween_factory(handler, registry): """ A :term:`tween` factory which produces a tween that catches an exception raised by downstream tweens (or the main Pyramid request handler) and, if possible, converts it into a Response using an :term:`exception view`.""" adapters = registry.adapters def excview_tween(request): attrs = request.__dict__ try: response = handler(request) except Exception as exc: # WARNING: do not assign the result of sys.exc_info() to a local # var here, doing so will cause a leak. We used to actually # explicitly delete both "exception" and "exc_info" from ``attrs`` # in a ``finally:`` clause below, but now we do not because these # attributes are useful to upstream tweens. This actually still # apparently causes a reference cycle, but it is broken # successfully by the garbage collector (see # https://github.com/Pylons/pyramid/issues/1223). attrs['exc_info'] = sys.exc_info() attrs['exception'] = exc # clear old generated request.response, if any; it may # have been mutated by the view, and its state is not # sane (e.g. caching headers) if 'response' in attrs: del attrs['response'] # we use .get instead of .__getitem__ below due to # https://github.com/Pylons/pyramid/issues/700 request_iface = attrs.get('request_iface', IRequest) provides = providedBy(exc) for_ = (IExceptionViewClassifier, request_iface.combined, provides) view_callable = adapters.lookup(for_, IView, default=None) if view_callable is None: raise response = view_callable(exc, request) return response return excview_tween
MAIN = 'MAIN' INGRESS = 'INGRESS' EXCVIEW = 'pyramid.tweens.excview_tween_factory'