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import warnings
from webob import exc
from secure import handle_security, cross_boundary
from util import iscontroller
__all__ = ['lookup_controller', 'find_object']
class NonCanonicalPath(Exception):
'''
Exception Raised when a non-canonical path is encountered when 'walking'
the URI. This is typically a ``POST`` request which requires a trailing
slash.
'''
def __init__(self, controller, remainder):
self.controller = controller
self.remainder = remainder
def lookup_controller(obj, url_path):
'''
Traverses the requested url path and returns the appropriate controller
object, including default routes.
Handles common errors gracefully.
'''
remainder = url_path
notfound_handlers = []
while True:
try:
obj, remainder = find_object(obj, remainder, notfound_handlers)
handle_security(obj)
return obj, remainder
except exc.HTTPNotFound:
while notfound_handlers:
name, obj, remainder = notfound_handlers.pop()
if name == '_default':
# Notfound handler is, in fact, a controller, so stop
# traversal
return obj, remainder
else:
# Notfound handler is an internal redirect, so continue
# traversal
result = handle_lookup_traversal(obj, remainder)
if result:
return lookup_controller(*result)
else:
raise exc.HTTPNotFound
def handle_lookup_traversal(obj, args):
try:
result = obj(*args)
if result:
prev_obj = obj
obj, remainder = result
# crossing controller boundary
cross_boundary(prev_obj, obj)
return result
except TypeError as te:
msg = 'Got exception calling lookup(): %s (%s)'
warnings.warn(
msg % (te, te.args),
RuntimeWarning
)
def find_object(obj, remainder, notfound_handlers):
'''
'Walks' the url path in search of an action for which a controller is
implemented and returns that controller object along with what's left
of the remainder.
'''
prev_obj = None
while True:
if obj is None:
raise exc.HTTPNotFound
if iscontroller(obj):
return obj, remainder
# are we traversing to another controller
cross_boundary(prev_obj, obj)
if remainder and remainder[0] == '':
index = getattr(obj, 'index', None)
if iscontroller(index):
return index, remainder[1:]
elif not remainder:
# the URL has hit an index method without a trailing slash
index = getattr(obj, 'index', None)
if iscontroller(index):
raise NonCanonicalPath(index, remainder[1:])
default = getattr(obj, '_default', None)
if iscontroller(default):
notfound_handlers.append(('_default', default, remainder))
lookup = getattr(obj, '_lookup', None)
if iscontroller(lookup):
notfound_handlers.append(('_lookup', lookup, remainder))
route = getattr(obj, '_route', None)
if iscontroller(route):
next, next_remainder = route(remainder)
cross_boundary(route, next)
return next, next_remainder
if not remainder:
raise exc.HTTPNotFound
next, remainder = remainder[0], remainder[1:]
prev_obj = obj
obj = getattr(obj, next, None)
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