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from __future__ import annotations
from typing import Any
from pydispatch import dispatcher
from twisted.internet.defer import Deferred
from scrapy.utils import signal as _signal
from scrapy.utils.defer import maybe_deferred_to_future
class SignalManager:
def __init__(self, sender: Any = dispatcher.Anonymous):
self.sender: Any = sender
def connect(self, receiver: Any, signal: Any, **kwargs: Any) -> None:
"""
Connect a receiver function to a signal.
The signal can be any object, although Scrapy comes with some
predefined signals that are documented in the :ref:`topics-signals`
section.
:param receiver: the function to be connected
:type receiver: collections.abc.Callable
:param signal: the signal to connect to
:type signal: object
"""
kwargs.setdefault("sender", self.sender)
dispatcher.connect(receiver, signal, **kwargs)
def disconnect(self, receiver: Any, signal: Any, **kwargs: Any) -> None:
"""
Disconnect a receiver function from a signal. This has the
opposite effect of the :meth:`connect` method, and the arguments
are the same.
"""
kwargs.setdefault("sender", self.sender)
dispatcher.disconnect(receiver, signal, **kwargs)
def send_catch_log(self, signal: Any, **kwargs: Any) -> list[tuple[Any, Any]]:
"""
Send a signal, catch exceptions and log them.
The keyword arguments are passed to the signal handlers (connected
through the :meth:`connect` method).
"""
kwargs.setdefault("sender", self.sender)
return _signal.send_catch_log(signal, **kwargs)
def send_catch_log_deferred(
self, signal: Any, **kwargs: Any
) -> Deferred[list[tuple[Any, Any]]]:
"""
Like :meth:`send_catch_log` but supports returning
:class:`~twisted.internet.defer.Deferred` objects from signal handlers.
Returns a Deferred that gets fired once all signal handlers
deferreds were fired. Send a signal, catch exceptions and log them.
The keyword arguments are passed to the signal handlers (connected
through the :meth:`connect` method).
"""
kwargs.setdefault("sender", self.sender)
return _signal.send_catch_log_deferred(signal, **kwargs)
def disconnect_all(self, signal: Any, **kwargs: Any) -> None:
"""
Disconnect all receivers from the given signal.
:param signal: the signal to disconnect from
:type signal: object
"""
kwargs.setdefault("sender", self.sender)
_signal.disconnect_all(signal, **kwargs)
async def wait_for(self, signal):
"""Await the next *signal*.
See :ref:`start-requests-lazy` for an example.
"""
d = Deferred()
def handle():
self.disconnect(handle, signal)
d.callback(None)
self.connect(handle, signal)
await maybe_deferred_to_future(d)
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