django-filtersignals/__init__.py

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2020-12-31 14:17:06 +00:00
from django.dispatch.dispatcher import Signal, NO_RECEIVERS, _make_id
from django.utils.inspect import func_accepts_kwargs
import weakref
class FilterSignal(Signal):
def connect(self, receiver, priority, sender=None, weak=True, dispatch_uid=None):
"""
Connect receiver to sender for signal.
Arguments:
receiver
A function or an instance method which is to receive signals.
Receivers must be hashable objects.
If weak is True, then receiver must be weak referenceable.
Receivers must be able to accept keyword arguments.
If a receiver is connected with a dispatch_uid argument, it
will not be added if another receiver was already connected
with that dispatch_uid.
priority
A numerical value indicating the order in which receivers are
called. The higher the value, the lower the priority.
sender
The sender to which the receiver should respond. Must either be
a Python object, or None to receive events from any sender.
weak
Whether to use weak references to the receiver. By default, the
module will attempt to use weak references to the receiver
objects. If this parameter is false, then strong references will
be used.
dispatch_uid
An identifier used to uniquely identify a particular instance of
a receiver. This will usually be a string, though it may be
anything hashable.
"""
from django.conf import settings
# If DEBUG is on, check that we got a good receiver
if settings.configured and settings.DEBUG:
assert callable(receiver), "Signal receivers must be callable."
# Check for **kwargs
if not func_accepts_kwargs(receiver):
raise ValueError("Signal receivers must accept keyword arguments (**kwargs).")
if dispatch_uid:
lookup_key = (dispatch_uid, _make_id(sender))
else:
lookup_key = (_make_id(receiver), _make_id(sender))
if weak:
ref = weakref.ref
receiver_object = receiver
# Check for bound methods
if hasattr(receiver, '__self__') and hasattr(receiver, '__func__'):
ref = weakref.WeakMethod
receiver_object = receiver.__self__
receiver = ref(receiver)
weakref.finalize(receiver_object, self._remove_receiver)
with self.lock:
self._clear_dead_receivers()
if not any(r_key == lookup_key for r_key, _, __ in self.receivers):
self.receivers.append((lookup_key, receiver, priority))
self.sender_receivers_cache.clear()
def disconnect(self, receiver=None, sender=None, dispatch_uid=None):
"""
Disconnect receiver from sender for signal.
If weak references are used, disconnect need not be called. The receiver
will be removed from dispatch automatically.
Arguments:
receiver
The registered receiver to disconnect. May be none if
dispatch_uid is specified.
sender
The registered sender to disconnect
dispatch_uid
the unique identifier of the receiver to disconnect
"""
if dispatch_uid:
lookup_key = (dispatch_uid, _make_id(sender))
else:
lookup_key = (_make_id(receiver), _make_id(sender))
disconnected = False
with self.lock:
self._clear_dead_receivers()
for index in range(len(self.receivers)):
(r_key, _, __) = self.receivers[index]
if r_key == lookup_key:
disconnected = True
del self.receivers[index]
break
self.sender_receivers_cache.clear()
return disconnected
def send(self, sender, **named):
"""
Send signal from sender to all connected receivers.
If any receiver raises an error, the error propagates back through send,
terminating the dispatch loop. So it's possible that all receivers
won't be called if an error is raised.
Receivers must return a dict with argument names from **named as keys
and the new data as values. If a key is not provided, its value is
unchanged.
Arguments:
sender
The sender of the signal. Either a specific object or None.
named
Named arguments which will be passed to receivers.
Return a dict of values processed by receivers.
"""
if not self.receivers or self.sender_receivers_cache.get(sender) is NO_RECEIVERS:
return named
for receiver in self._live_receivers(sender):
return [
(receiver, receiver(signal=self, sender=sender, **named))
for receiver in self._live_receivers(sender)
]
def send_robust(self, sender, **named):
"""
Send signal from sender to all connected receivers catching errors.
Arguments:
sender
The sender of the signal. Can be any Python object (normally one
registered with a connect if you actually want something to
occur).
named
Named arguments which will be passed to receivers. These
arguments must be a subset of the argument names defined in
providing_args.
Return a list of tuple pairs [(receiver, response), ... ].
Return a dict of values processed by receivers.
If any receiver raises an error (specifically any subclass of
Exception), return it as a (receiver, error) tuple under the
"_errors" key.
"""
if not self.receivers or self.sender_receivers_cache.get(sender) is NO_RECEIVERS:
return []
# Call each receiver with whatever arguments it can accept.
# Return a list of tuple pairs [(receiver, response), ... ].
responses = []
for receiver in self._live_receivers(sender):
try:
response = receiver(signal=self, sender=sender, **named)
except Exception as err:
responses.append((receiver, err))
else:
responses.append((receiver, response))
return responses
def receiver(signal, priority, **kwargs):
"""
A decorator for connecting receivers to signals. Used by passing in the
signal (or list of signals), the requested priority, and keyword
arguments to connect:
@receiver(post_save, 0, sender=MyModel)
def signal_receiver(sender, **kwargs):
...
@receiver([post_save, post_delete], 0, sender=MyModel)
def signals_receiver(sender, **kwargs):
...
"""
def _decorator(func):
if isinstance(signal, (list, tuple)):
for s in signal:
s.connect(func, priority **kwargs)
else:
signal.connect(func, priority, **kwargs)
return func
return _decorator