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