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core.py
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core.py
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"""The core WSGIController"""
import inspect
import logging
import types
import warnings
from paste.httpexceptions import HTTPException as LegacyHTTPException
from webob.exc import HTTPException, HTTPNotFound
import pylons
import pylons.legacy
__all__ = ['WSGIController']
log = logging.getLogger(__name__)
class WSGIController(object):
"""WSGI Controller that follows WSGI spec for calling and return
values
The Pylons WSGI Controller handles incoming web requests that are
dispatched from the PylonsBaseWSGIApp. These requests result in a
new instance of the WSGIController being created, which is then
called with the dict options from the Routes match. The standard
WSGI response is then returned with start_response called as per
the WSGI spec.
Special WSGIController methods you may define:
``__before__``
This method is called before your action is, and should be used
for setting up variables/objects, restricting access to other
actions, or other tasks which should be executed before the
action is called.
``__after__``
This method is called after the action is, unless an unexpected
exception was raised. Subclasses of
:class:`~webob.exc.HTTPException` (such as those raised by
``redirect_to`` and ``abort``) are expected; e.g. ``__after__``
will be called on redirects.
Each action to be called is inspected with :meth:`_inspect_call` so
that it is only passed the arguments in the Routes match dict that
it asks for. The arguments passed into the action can be customized
by overriding the :meth:`_get_method_args` function which is
expected to return a dict.
In the event that an action is not found to handle the request, the
Controller will raise an "Action Not Found" error if in debug mode,
otherwise a ``404 Not Found`` error will be returned.
"""
_pylons_log_debug = False
def _perform_call(self, func, args):
"""Hide the traceback for everything above this method"""
__traceback_hide__ = 'before_and_this'
return func(**args)
def _inspect_call(self, func):
"""Calls a function with arguments from
:meth:`_get_method_args`
Given a function, inspect_call will inspect the function args
and call it with no further keyword args than it asked for.
If the function has been decorated, it is assumed that the
decorator preserved the function signature.
"""
# Check to see if the class has a cache of argspecs yet
try:
cached_argspecs = self.__class__._cached_argspecs
except AttributeError:
self.__class__._cached_argspecs = cached_argspecs = {}
try:
argspec = cached_argspecs[func.im_func]
except KeyError:
argspec = cached_argspecs[func.im_func] = inspect.getargspec(func)
kargs = self._get_method_args()
log_debug = self._pylons_log_debug
c = self._py_object.c
environ = self._py_object.request.environ
args = None
if argspec[2]:
if self._py_object.config['pylons.c_attach_args']:
for k, val in kargs.iteritems():
setattr(c, k, val)
args = kargs
else:
args = {}
argnames = argspec[0][isinstance(func, types.MethodType)
and 1 or 0:]
for name in argnames:
if name in kargs:
if self._py_object.config['pylons.c_attach_args']:
setattr(c, name, kargs[name])
args[name] = kargs[name]
if log_debug:
log.debug("Calling %r method with keyword args: **%r",
func.__name__, args)
try:
result = self._perform_call(func, args)
except HTTPException, httpe:
if log_debug:
log.debug("%r method raised HTTPException: %s (code: %s)",
func.__name__, httpe.__class__.__name__,
httpe.wsgi_response.code, exc_info=True)
result = httpe
# Store the exception in the environ
environ['pylons.controller.exception'] = httpe
# 304 Not Modified's shouldn't have a content-type set
if result.wsgi_response.status_int == 304:
result.wsgi_response.headers.pop('Content-Type', None)
result._exception = True
except LegacyHTTPException, httpe:
if log_debug:
log.debug("%r method raised legacy HTTPException: %s (code: "
"%s)", func.__name__, httpe.__class__.__name__,
httpe.code, exc_info=True)
warnings.warn("Raising a paste.httpexceptions.HTTPException is "
"deprecated, use webob.exc.HTTPException instead",
DeprecationWarning, 2)
result = httpe.response(environ)
result.headers.pop('Content-Type')
result._exception = True
return result
def _get_method_args(self):
"""Retrieve the method arguments to use with inspect call
By default, this uses Routes to retrieve the arguments,
override this method to customize the arguments your controller
actions are called with.
This method should return a dict.
"""
req = self._py_object.request
kargs = req.environ['pylons.routes_dict'].copy()
kargs['environ'] = req.environ
kargs['start_response'] = self.start_response
kargs['pylons'] = self._py_object
return kargs
def _dispatch_call(self):
"""Handles dispatching the request to the function using
Routes"""
log_debug = self._pylons_log_debug
req = self._py_object.request
try:
action = req.environ['pylons.routes_dict']['action']
except KeyError:
raise Exception("No action matched from Routes, unable to"
"determine action dispatch.")
action_method = action.replace('-', '_')
if log_debug:
log.debug("Looking for %r method to handle the request",
action_method)
try:
func = getattr(self, action_method, None)
except UnicodeEncodeError:
func = None
if action_method != 'start_response' and callable(func):
# Store function used to handle request
req.environ['pylons.action_method'] = func
response = self._inspect_call(func)
else:
if log_debug:
log.debug("Couldn't find %r method to handle response", action)
if pylons.config['debug']:
raise NotImplementedError('Action %r is not implemented' %
action)
else:
response = HTTPNotFound()
return response
def __call__(self, environ, start_response):
"""The main call handler that is called to return a response"""
log_debug = self._pylons_log_debug
# Keep a local reference to the req/response objects
self._py_object = environ['pylons.pylons']
# Keep private methods private
try:
if environ['pylons.routes_dict']['action'][:1] in ('_', '-'):
if log_debug:
log.debug("Action starts with _, private action not "
"allowed. Returning a 404 response")
return HTTPNotFound()(environ, start_response)
except KeyError:
# The check later will notice that there's no action
pass
start_response_called = []
def repl_start_response(status, headers, exc_info=None):
response = self._py_object.response
start_response_called.append(None)
# Copy the headers from the global response
if log_debug:
log.debug("Merging pylons.response headers into "
"start_response call, status: %s", status)
for header in response.headerlist:
if header[0] == 'Set-Cookie' or header[0].startswith('X-'):
headers.append(header)
return start_response(status, headers, exc_info)
self.start_response = repl_start_response
if hasattr(self, '__before__'):
response = self._inspect_call(self.__before__)
if hasattr(response, '_exception'):
return response(environ, self.start_response)
response = self._dispatch_call()
if not start_response_called:
self.start_response = start_response
py_response = self._py_object.response
# If its not a WSGI response, and we have content, it needs to
# be wrapped in the response object
if isinstance(response, str):
if log_debug:
log.debug("Controller returned a string "
", writing it to pylons.response")
py_response.body = py_response.body + response
elif isinstance(response, unicode):
if log_debug:
log.debug("Controller returned a unicode string "
", writing it to pylons.response")
py_response.unicode_body = py_response.unicode_body + \
response
elif hasattr(response, 'wsgi_response'):
# It's either a legacy WSGIResponse object, or an exception
# that got tossed.
if log_debug:
log.debug("Controller returned a Response object, merging "
"it with pylons.response")
if response is pylons.response:
# Only etag_cache() returns pylons.response
# (deprecated). Unwrap it to avoid a recursive loop
# (see ticket #508)
response = response._current_obj()
warnings.warn(pylons.legacy.response_warning,
DeprecationWarning, 1)
for name, value in py_response.headers.items():
if name.lower() == 'set-cookie':
response.headers.add(name, value)
else:
response.headers.setdefault(name, value)
try:
registry = environ['paste.registry']
registry.replace(pylons.response, response)
except KeyError:
# Ignore the case when someone removes the registry
pass
py_response = response
elif response is None:
if log_debug:
log.debug("Controller returned None")
else:
if log_debug:
log.debug("Assuming controller returned an iterable, "
"setting it as pylons.response.app_iter")
py_response.app_iter = response
response = py_response
if hasattr(self, '__after__'):
after = self._inspect_call(self.__after__)
if hasattr(after, '_exception'):
return after(environ, self.start_response)
if hasattr(response, 'wsgi_response'):
# Copy the response object into the testing vars if we're testing
if 'paste.testing_variables' in environ:
environ['paste.testing_variables']['response'] = response
if log_debug:
log.debug("Calling Response object to return WSGI data")
return response(environ, self.start_response)
if log_debug:
log.debug("Response assumed to be WSGI content, returning "
"un-touched")
return response