407 lines
14 KiB
Python
407 lines
14 KiB
Python
# (c) 2005 Ian Bicking and contributors; written for Paste (http://pythonpaste.org)
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# Licensed under the MIT license: http://www.opensource.org/licenses/mit-license.php
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"""
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Middleware to make internal requests and forward requests internally.
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When applied, several keys are added to the environment that will allow
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you to trigger recursive redirects and forwards.
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paste.recursive.include:
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When you call
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``environ['paste.recursive.include'](new_path_info)`` a response
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will be returned. The response has a ``body`` attribute, a
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``status`` attribute, and a ``headers`` attribute.
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paste.recursive.script_name:
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The ``SCRIPT_NAME`` at the point that recursive lives. Only
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paths underneath this path can be redirected to.
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paste.recursive.old_path_info:
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A list of previous ``PATH_INFO`` values from previous redirects.
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Raise ``ForwardRequestException(new_path_info)`` to do a forward
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(aborting the current request).
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"""
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import six
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import warnings
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from six.moves import cStringIO as StringIO
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__all__ = ['RecursiveMiddleware']
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__pudge_all__ = ['RecursiveMiddleware', 'ForwardRequestException']
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class RecursionLoop(AssertionError):
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# Subclasses AssertionError for legacy reasons
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"""Raised when a recursion enters into a loop"""
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class CheckForRecursionMiddleware(object):
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def __init__(self, app, env):
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self.app = app
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self.env = env
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def __call__(self, environ, start_response):
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path_info = environ.get('PATH_INFO','')
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if path_info in self.env.get(
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'paste.recursive.old_path_info', []):
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raise RecursionLoop(
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"Forwarding loop detected; %r visited twice (internal "
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"redirect path: %s)"
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% (path_info, self.env['paste.recursive.old_path_info']))
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old_path_info = self.env.setdefault('paste.recursive.old_path_info', [])
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old_path_info.append(self.env.get('PATH_INFO', ''))
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return self.app(environ, start_response)
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class RecursiveMiddleware(object):
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"""
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A WSGI middleware that allows for recursive and forwarded calls.
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All these calls go to the same 'application', but presumably that
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application acts differently with different URLs. The forwarded
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URLs must be relative to this container.
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Interface is entirely through the ``paste.recursive.forward`` and
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``paste.recursive.include`` environmental keys.
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"""
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def __init__(self, application, global_conf=None):
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self.application = application
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def __call__(self, environ, start_response):
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environ['paste.recursive.forward'] = Forwarder(
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self.application,
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environ,
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start_response)
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environ['paste.recursive.include'] = Includer(
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self.application,
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environ,
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start_response)
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environ['paste.recursive.include_app_iter'] = IncluderAppIter(
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self.application,
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environ,
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start_response)
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my_script_name = environ.get('SCRIPT_NAME', '')
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environ['paste.recursive.script_name'] = my_script_name
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try:
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return self.application(environ, start_response)
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except ForwardRequestException as e:
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middleware = CheckForRecursionMiddleware(
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e.factory(self), environ)
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return middleware(environ, start_response)
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class ForwardRequestException(Exception):
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"""
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Used to signal that a request should be forwarded to a different location.
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``url``
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The URL to forward to starting with a ``/`` and relative to
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``RecursiveMiddleware``. URL fragments can also contain query strings
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so ``/error?code=404`` would be a valid URL fragment.
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``environ``
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An altertative WSGI environment dictionary to use for the forwarded
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request. If specified is used *instead* of the ``url_fragment``
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``factory``
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If specifed ``factory`` is used instead of ``url`` or ``environ``.
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``factory`` is a callable that takes a WSGI application object
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as the first argument and returns an initialised WSGI middleware
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which can alter the forwarded response.
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Basic usage (must have ``RecursiveMiddleware`` present) :
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.. code-block:: python
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from paste.recursive import ForwardRequestException
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def app(environ, start_response):
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if environ['PATH_INFO'] == '/hello':
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start_response("200 OK", [('Content-type', 'text/plain')])
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return [b'Hello World!']
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elif environ['PATH_INFO'] == '/error':
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start_response("404 Not Found", [('Content-type', 'text/plain')])
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return [b'Page not found']
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else:
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raise ForwardRequestException('/error')
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from paste.recursive import RecursiveMiddleware
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app = RecursiveMiddleware(app)
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If you ran this application and visited ``/hello`` you would get a
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``Hello World!`` message. If you ran the application and visited
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``/not_found`` a ``ForwardRequestException`` would be raised and the caught
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by the ``RecursiveMiddleware``. The ``RecursiveMiddleware`` would then
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return the headers and response from the ``/error`` URL but would display
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a ``404 Not found`` status message.
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You could also specify an ``environ`` dictionary instead of a url. Using
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the same example as before:
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.. code-block:: python
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def app(environ, start_response):
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... same as previous example ...
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else:
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new_environ = environ.copy()
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new_environ['PATH_INFO'] = '/error'
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raise ForwardRequestException(environ=new_environ)
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Finally, if you want complete control over every aspect of the forward you
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can specify a middleware factory. For example to keep the old status code
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but use the headers and resposne body from the forwarded response you might
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do this:
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.. code-block:: python
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from paste.recursive import ForwardRequestException
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from paste.recursive import RecursiveMiddleware
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from paste.errordocument import StatusKeeper
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def app(environ, start_response):
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if environ['PATH_INFO'] == '/hello':
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start_response("200 OK", [('Content-type', 'text/plain')])
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return [b'Hello World!']
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elif environ['PATH_INFO'] == '/error':
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start_response("404 Not Found", [('Content-type', 'text/plain')])
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return [b'Page not found']
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else:
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def factory(app):
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return StatusKeeper(app, status='404 Not Found', url='/error')
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raise ForwardRequestException(factory=factory)
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app = RecursiveMiddleware(app)
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"""
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def __init__(
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self,
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url=None,
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environ={},
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factory=None,
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path_info=None):
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# Check no incompatible options have been chosen
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if factory and url:
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raise TypeError(
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'You cannot specify factory and a url in '
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'ForwardRequestException')
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elif factory and environ:
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raise TypeError(
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'You cannot specify factory and environ in '
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'ForwardRequestException')
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if url and environ:
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raise TypeError(
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'You cannot specify environ and url in '
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'ForwardRequestException')
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# set the path_info or warn about its use.
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if path_info:
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if not url:
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warnings.warn(
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"ForwardRequestException(path_info=...) has been deprecated; please "
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"use ForwardRequestException(url=...)",
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DeprecationWarning, 2)
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else:
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raise TypeError('You cannot use url and path_info in ForwardRequestException')
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self.path_info = path_info
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# If the url can be treated as a path_info do that
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if url and not '?' in str(url):
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self.path_info = url
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# Base middleware
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class ForwardRequestExceptionMiddleware(object):
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def __init__(self, app):
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self.app = app
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# Otherwise construct the appropriate middleware factory
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if hasattr(self, 'path_info'):
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p = self.path_info
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def factory_(app):
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class PathInfoForward(ForwardRequestExceptionMiddleware):
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def __call__(self, environ, start_response):
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environ['PATH_INFO'] = p
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return self.app(environ, start_response)
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return PathInfoForward(app)
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self.factory = factory_
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elif url:
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def factory_(app):
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class URLForward(ForwardRequestExceptionMiddleware):
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def __call__(self, environ, start_response):
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environ['PATH_INFO'] = url.split('?')[0]
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environ['QUERY_STRING'] = url.split('?')[1]
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return self.app(environ, start_response)
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return URLForward(app)
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self.factory = factory_
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elif environ:
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def factory_(app):
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class EnvironForward(ForwardRequestExceptionMiddleware):
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def __call__(self, environ_, start_response):
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return self.app(environ, start_response)
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return EnvironForward(app)
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self.factory = factory_
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else:
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self.factory = factory
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class Recursive(object):
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def __init__(self, application, environ, start_response):
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self.application = application
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self.original_environ = environ.copy()
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self.previous_environ = environ
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self.start_response = start_response
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def __call__(self, path, extra_environ=None):
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"""
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`extra_environ` is an optional dictionary that is also added
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to the forwarded request. E.g., ``{'HTTP_HOST': 'new.host'}``
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could be used to forward to a different virtual host.
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"""
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environ = self.original_environ.copy()
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if extra_environ:
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environ.update(extra_environ)
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environ['paste.recursive.previous_environ'] = self.previous_environ
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base_path = self.original_environ.get('SCRIPT_NAME')
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if path.startswith('/'):
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assert path.startswith(base_path), (
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"You can only forward requests to resources under the "
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"path %r (not %r)" % (base_path, path))
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path = path[len(base_path)+1:]
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assert not path.startswith('/')
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path_info = '/' + path
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environ['PATH_INFO'] = path_info
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environ['REQUEST_METHOD'] = 'GET'
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environ['CONTENT_LENGTH'] = '0'
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environ['CONTENT_TYPE'] = ''
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environ['wsgi.input'] = StringIO('')
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return self.activate(environ)
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def activate(self, environ):
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raise NotImplementedError
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def __repr__(self):
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return '<%s.%s from %s>' % (
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self.__class__.__module__,
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self.__class__.__name__,
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self.original_environ.get('SCRIPT_NAME') or '/')
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class Forwarder(Recursive):
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"""
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The forwarder will try to restart the request, except with
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the new `path` (replacing ``PATH_INFO`` in the request).
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It must not be called after and headers have been returned.
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It returns an iterator that must be returned back up the call
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stack, so it must be used like:
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.. code-block:: python
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return environ['paste.recursive.forward'](path)
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Meaningful transformations cannot be done, since headers are
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sent directly to the server and cannot be inspected or
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rewritten.
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"""
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def activate(self, environ):
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warnings.warn(
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"recursive.Forwarder has been deprecated; please use "
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"ForwardRequestException",
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DeprecationWarning, 2)
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return self.application(environ, self.start_response)
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class Includer(Recursive):
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"""
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Starts another request with the given path and adding or
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overwriting any values in the `extra_environ` dictionary.
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Returns an IncludeResponse object.
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"""
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def activate(self, environ):
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response = IncludedResponse()
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def start_response(status, headers, exc_info=None):
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if exc_info:
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six.reraise(exc_info[0], exc_info[1], exc_info[2])
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response.status = status
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response.headers = headers
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return response.write
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app_iter = self.application(environ, start_response)
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try:
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for s in app_iter:
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response.write(s)
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finally:
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if hasattr(app_iter, 'close'):
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app_iter.close()
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response.close()
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return response
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class IncludedResponse(object):
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def __init__(self):
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self.headers = None
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self.status = None
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self.output = StringIO()
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self.str = None
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def close(self):
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self.str = self.output.getvalue()
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self.output.close()
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self.output = None
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def write(self, s):
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assert self.output is not None, (
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"This response has already been closed and no further data "
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"can be written.")
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self.output.write(s)
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def __str__(self):
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return self.body
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def body__get(self):
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if self.str is None:
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return self.output.getvalue()
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else:
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return self.str
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body = property(body__get)
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class IncluderAppIter(Recursive):
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"""
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Like Includer, but just stores the app_iter response
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(be sure to call close on the response!)
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"""
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def activate(self, environ):
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response = IncludedAppIterResponse()
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def start_response(status, headers, exc_info=None):
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if exc_info:
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six.reraise(exc_info[0], exc_info[1], exc_info[2])
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response.status = status
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response.headers = headers
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return response.write
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app_iter = self.application(environ, start_response)
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response.app_iter = app_iter
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return response
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class IncludedAppIterResponse(object):
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def __init__(self):
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self.status = None
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self.headers = None
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self.accumulated = []
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self.app_iter = None
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self._closed = False
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def close(self):
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assert not self._closed, (
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"Tried to close twice")
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if hasattr(self.app_iter, 'close'):
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self.app_iter.close()
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def write(self, s):
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self.accumulated.append
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def make_recursive_middleware(app, global_conf):
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return RecursiveMiddleware(app)
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make_recursive_middleware.__doc__ = __doc__
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