from __future__ import annotations import collections.abc as c import typing as t import warnings import weakref from collections import defaultdict from contextlib import AbstractContextManager from contextlib import contextmanager from functools import cached_property from inspect import iscoroutinefunction from weakref import WeakValueDictionary from ._utilities import make_id from ._utilities import make_ref from ._utilities import Symbol if t.TYPE_CHECKING: F = t.TypeVar("F", bound=c.Callable[..., t.Any]) ANY = Symbol("ANY") """Symbol for "any sender".""" ANY_ID = 0 class Signal: """A notification emitter. :param doc: The docstring for the signal. """ ANY = ANY """An alias for the :data:`~blinker.ANY` sender symbol.""" set_class: type[set[t.Any]] = set """The set class to use for tracking connected receivers and senders. Python's ``set`` is unordered. If receivers must be dispatched in the order they were connected, an ordered set implementation can be used. .. versionadded:: 1.7 """ @cached_property def receiver_connected(self) -> Signal: """Emitted at the end of each :meth:`connect` call. The signal sender is the signal instance, and the :meth:`connect` arguments are passed through: ``receiver``, ``sender``, and ``weak``. .. versionadded:: 1.2 """ return Signal(doc="Emitted after a receiver connects.") @cached_property def receiver_disconnected(self) -> Signal: """Emitted at the end of each :meth:`disconnect` call. The sender is the signal instance, and the :meth:`disconnect` arguments are passed through: ``receiver`` and ``sender``. This signal is emitted **only** when :meth:`disconnect` is called explicitly. This signal cannot be emitted by an automatic disconnect when a weakly referenced receiver or sender goes out of scope, as the instance is no longer be available to be used as the sender for this signal. An alternative approach is available by subscribing to :attr:`receiver_connected` and setting up a custom weakref cleanup callback on weak receivers and senders. .. versionadded:: 1.2 """ return Signal(doc="Emitted after a receiver disconnects.") def __init__(self, doc: str | None = None) -> None: if doc: self.__doc__ = doc self.receivers: dict[ t.Any, weakref.ref[c.Callable[..., t.Any]] | c.Callable[..., t.Any] ] = {} """The map of connected receivers. Useful to quickly check if any receivers are connected to the signal: ``if s.receivers:``. The structure and data is not part of the public API, but checking its boolean value is. """ self.is_muted: bool = False self._by_receiver: dict[t.Any, set[t.Any]] = defaultdict(self.set_class) self._by_sender: dict[t.Any, set[t.Any]] = defaultdict(self.set_class) self._weak_senders: dict[t.Any, weakref.ref[t.Any]] = {} def connect(self, receiver: F, sender: t.Any = ANY, weak: bool = True) -> F: """Connect ``receiver`` to be called when the signal is sent by ``sender``. :param receiver: The callable to call when :meth:`send` is called with the given ``sender``, passing ``sender`` as a positional argument along with any extra keyword arguments. :param sender: Any object or :data:`ANY`. ``receiver`` will only be called when :meth:`send` is called with this sender. If ``ANY``, the receiver will be called for any sender. A receiver may be connected to multiple senders by calling :meth:`connect` multiple times. :param weak: Track the receiver with a :mod:`weakref`. The receiver will be automatically disconnected when it is garbage collected. When connecting a receiver defined within a function, set to ``False``, otherwise it will be disconnected when the function scope ends. """ receiver_id = make_id(receiver) sender_id = ANY_ID if sender is ANY else make_id(sender) if weak: self.receivers[receiver_id] = make_ref( receiver, self._make_cleanup_receiver(receiver_id) ) else: self.receivers[receiver_id] = receiver self._by_sender[sender_id].add(receiver_id) self._by_receiver[receiver_id].add(sender_id) if sender is not ANY and sender_id not in self._weak_senders: # store a cleanup for weakref-able senders try: self._weak_senders[sender_id] = make_ref( sender, self._make_cleanup_sender(sender_id) ) except TypeError: pass if "receiver_connected" in self.__dict__ and self.receiver_connected.receivers: try: self.receiver_connected.send( self, receiver=receiver, sender=sender, weak=weak ) except TypeError: # TODO no explanation or test for this self.disconnect(receiver, sender) raise if _receiver_connected.receivers and self is not _receiver_connected: try: _receiver_connected.send( self, receiver_arg=receiver, sender_arg=sender, weak_arg=weak ) except TypeError: self.disconnect(receiver, sender) raise return receiver def connect_via(self, sender: t.Any, weak: bool = False) -> c.Callable[[F], F]: """Connect the decorated function to be called when the signal is sent by ``sender``. The decorated function will be called when :meth:`send` is called with the given ``sender``, passing ``sender`` as a positional argument along with any extra keyword arguments. :param sender: Any object or :data:`ANY`. ``receiver`` will only be called when :meth:`send` is called with this sender. If ``ANY``, the receiver will be called for any sender. A receiver may be connected to multiple senders by calling :meth:`connect` multiple times. :param weak: Track the receiver with a :mod:`weakref`. The receiver will be automatically disconnected when it is garbage collected. When connecting a receiver defined within a function, set to ``False``, otherwise it will be disconnected when the function scope ends.= .. versionadded:: 1.1 """ def decorator(fn: F) -> F: self.connect(fn, sender, weak) return fn return decorator @contextmanager def connected_to( self, receiver: c.Callable[..., t.Any], sender: t.Any = ANY ) -> c.Generator[None, None, None]: """A context manager that temporarily connects ``receiver`` to the signal while a ``with`` block executes. When the block exits, the receiver is disconnected. Useful for tests. :param receiver: The callable to call when :meth:`send` is called with the given ``sender``, passing ``sender`` as a positional argument along with any extra keyword arguments. :param sender: Any object or :data:`ANY`. ``receiver`` will only be called when :meth:`send` is called with this sender. If ``ANY``, the receiver will be called for any sender. .. versionadded:: 1.1 """ self.connect(receiver, sender=sender, weak=False) try: yield None finally: self.disconnect(receiver) @contextmanager def muted(self) -> c.Generator[None, None, None]: """A context manager that temporarily disables the signal. No receivers will be called if the signal is sent, until the ``with`` block exits. Useful for tests. """ self.is_muted = True try: yield None finally: self.is_muted = False def temporarily_connected_to( self, receiver: c.Callable[..., t.Any], sender: t.Any = ANY ) -> AbstractContextManager[None]: """Deprecated alias for :meth:`connected_to`. .. deprecated:: 1.1 Renamed to ``connected_to``. Will be removed in Blinker 1.9. .. versionadded:: 0.9 """ warnings.warn( "'temporarily_connected_to' is renamed to 'connected_to'. The old name is" " deprecated and will be removed in Blinker 1.9.", DeprecationWarning, stacklevel=2, ) return self.connected_to(receiver, sender) def send( self, sender: t.Any | None = None, /, *, _async_wrapper: c.Callable[ [c.Callable[..., c.Coroutine[t.Any, t.Any, t.Any]]], c.Callable[..., t.Any] ] | None = None, **kwargs: t.Any, ) -> list[tuple[c.Callable[..., t.Any], t.Any]]: """Call all receivers that are connected to the given ``sender`` or :data:`ANY`. Each receiver is called with ``sender`` as a positional argument along with any extra keyword arguments. Return a list of ``(receiver, return value)`` tuples. The order receivers are called is undefined, but can be influenced by setting :attr:`set_class`. If a receiver raises an exception, that exception will propagate up. This makes debugging straightforward, with an assumption that correctly implemented receivers will not raise. :param sender: Call receivers connected to this sender, in addition to those connected to :data:`ANY`. :param _async_wrapper: Will be called on any receivers that are async coroutines to turn them into sync callables. For example, could run the receiver with an event loop. :param kwargs: Extra keyword arguments to pass to each receiver. .. versionchanged:: 1.7 Added the ``_async_wrapper`` argument. """ if self.is_muted: return [] results = [] for receiver in self.receivers_for(sender): if iscoroutinefunction(receiver): if _async_wrapper is None: raise RuntimeError("Cannot send to a coroutine function.") result = _async_wrapper(receiver)(sender, **kwargs) else: result = receiver(sender, **kwargs) results.append((receiver, result)) return results async def send_async( self, sender: t.Any | None = None, /, *, _sync_wrapper: c.Callable[ [c.Callable[..., t.Any]], c.Callable[..., c.Coroutine[t.Any, t.Any, t.Any]] ] | None = None, **kwargs: t.Any, ) -> list[tuple[c.Callable[..., t.Any], t.Any]]: """Await all receivers that are connected to the given ``sender`` or :data:`ANY`. Each receiver is called with ``sender`` as a positional argument along with any extra keyword arguments. Return a list of ``(receiver, return value)`` tuples. The order receivers are called is undefined, but can be influenced by setting :attr:`set_class`. If a receiver raises an exception, that exception will propagate up. This makes debugging straightforward, with an assumption that correctly implemented receivers will not raise. :param sender: Call receivers connected to this sender, in addition to those connected to :data:`ANY`. :param _sync_wrapper: Will be called on any receivers that are sync callables to turn them into async coroutines. For example, could call the receiver in a thread. :param kwargs: Extra keyword arguments to pass to each receiver. .. versionadded:: 1.7 """ if self.is_muted: return [] results = [] for receiver in self.receivers_for(sender): if not iscoroutinefunction(receiver): if _sync_wrapper is None: raise RuntimeError("Cannot send to a non-coroutine function.") result = await _sync_wrapper(receiver)(sender, **kwargs) else: result = await receiver(sender, **kwargs) results.append((receiver, result)) return results def has_receivers_for(self, sender: t.Any) -> bool: """Check if there is at least one receiver that will be called with the given ``sender``. A receiver connected to :data:`ANY` will always be called, regardless of sender. Does not check if weakly referenced receivers are still live. See :meth:`receivers_for` for a stronger search. :param sender: Check for receivers connected to this sender, in addition to those connected to :data:`ANY`. """ if not self.receivers: return False if self._by_sender[ANY_ID]: return True if sender is ANY: return False return make_id(sender) in self._by_sender def receivers_for( self, sender: t.Any ) -> c.Generator[c.Callable[..., t.Any], None, None]: """Yield each receiver to be called for ``sender``, in addition to those to be called for :data:`ANY`. Weakly referenced receivers that are not live will be disconnected and skipped. :param sender: Yield receivers connected to this sender, in addition to those connected to :data:`ANY`. """ # TODO: test receivers_for(ANY) if not self.receivers: return sender_id = make_id(sender) if sender_id in self._by_sender: ids = self._by_sender[ANY_ID] | self._by_sender[sender_id] else: ids = self._by_sender[ANY_ID].copy() for receiver_id in ids: receiver = self.receivers.get(receiver_id) if receiver is None: continue if isinstance(receiver, weakref.ref): strong = receiver() if strong is None: self._disconnect(receiver_id, ANY_ID) continue yield strong else: yield receiver def disconnect(self, receiver: c.Callable[..., t.Any], sender: t.Any = ANY) -> None: """Disconnect ``receiver`` from being called when the signal is sent by ``sender``. :param receiver: A connected receiver callable. :param sender: Disconnect from only this sender. By default, disconnect from all senders. """ sender_id: c.Hashable if sender is ANY: sender_id = ANY_ID else: sender_id = make_id(sender) receiver_id = make_id(receiver) self._disconnect(receiver_id, sender_id) if ( "receiver_disconnected" in self.__dict__ and self.receiver_disconnected.receivers ): self.receiver_disconnected.send(self, receiver=receiver, sender=sender) def _disconnect(self, receiver_id: c.Hashable, sender_id: c.Hashable) -> None: if sender_id == ANY_ID: if self._by_receiver.pop(receiver_id, None) is not None: for bucket in self._by_sender.values(): bucket.discard(receiver_id) self.receivers.pop(receiver_id, None) else: self._by_sender[sender_id].discard(receiver_id) self._by_receiver[receiver_id].discard(sender_id) def _make_cleanup_receiver( self, receiver_id: c.Hashable ) -> c.Callable[[weakref.ref[c.Callable[..., t.Any]]], None]: """Create a callback function to disconnect a weakly referenced receiver when it is garbage collected. """ def cleanup(ref: weakref.ref[c.Callable[..., t.Any]]) -> None: self._disconnect(receiver_id, ANY_ID) return cleanup def _make_cleanup_sender( self, sender_id: c.Hashable ) -> c.Callable[[weakref.ref[t.Any]], None]: """Create a callback function to disconnect all receivers for a weakly referenced sender when it is garbage collected. """ assert sender_id != ANY_ID def cleanup(ref: weakref.ref[t.Any]) -> None: self._weak_senders.pop(sender_id, None) for receiver_id in self._by_sender.pop(sender_id, ()): self._by_receiver[receiver_id].discard(sender_id) return cleanup def _cleanup_bookkeeping(self) -> None: """Prune unused sender/receiver bookkeeping. Not threadsafe. Connecting & disconnecting leaves behind a small amount of bookkeeping data. Typical workloads using Blinker, for example in most web apps, Flask, CLI scripts, etc., are not adversely affected by this bookkeeping. With a long-running process performing dynamic signal routing with high volume, e.g. connecting to function closures, senders are all unique object instances. Doing all of this over and over may cause memory usage to grow due to extraneous bookkeeping. (An empty ``set`` for each stale sender/receiver pair.) This method will prune that bookkeeping away, with the caveat that such pruning is not threadsafe. The risk is that cleanup of a fully disconnected receiver/sender pair occurs while another thread is connecting that same pair. If you are in the highly dynamic, unique receiver/sender situation that has lead you to this method, that failure mode is perhaps not a big deal for you. """ for mapping in (self._by_sender, self._by_receiver): for ident, bucket in list(mapping.items()): if not bucket: mapping.pop(ident, None) def _clear_state(self) -> None: """Disconnect all receivers and senders. Useful for tests.""" self._weak_senders.clear() self.receivers.clear() self._by_sender.clear() self._by_receiver.clear() _receiver_connected = Signal( """\ Sent by a :class:`Signal` after a receiver connects. :argument: the Signal that was connected to :keyword receiver_arg: the connected receiver :keyword sender_arg: the sender to connect to :keyword weak_arg: true if the connection to receiver_arg is a weak reference .. deprecated:: 1.2 Individual signals have their own :attr:`~Signal.receiver_connected` and :attr:`~Signal.receiver_disconnected` signals with a slightly simplified call signature. This global signal will be removed in Blinker 1.9. """ ) class NamedSignal(Signal): """A named generic notification emitter. The name is not used by the signal itself, but matches the key in the :class:`Namespace` that it belongs to. :param name: The name of the signal within the namespace. :param doc: The docstring for the signal. """ def __init__(self, name: str, doc: str | None = None) -> None: super().__init__(doc) #: The name of this signal. self.name: str = name def __repr__(self) -> str: base = super().__repr__() return f"{base[:-1]}; {self.name!r}>" # noqa: E702 if t.TYPE_CHECKING: class PNamespaceSignal(t.Protocol): def __call__(self, name: str, doc: str | None = None) -> NamedSignal: ... # Python < 3.9 _NamespaceBase = dict[str, NamedSignal] # type: ignore[misc] else: _NamespaceBase = dict class Namespace(_NamespaceBase): """A dict mapping names to signals.""" def signal(self, name: str, doc: str | None = None) -> NamedSignal: """Return the :class:`NamedSignal` for the given ``name``, creating it if required. Repeated calls with the same name return the same signal. :param name: The name of the signal. :param doc: The docstring of the signal. """ if name not in self: self[name] = NamedSignal(name, doc) return self[name] class _WeakNamespace(WeakValueDictionary): # type: ignore[type-arg] """A weak mapping of names to signals. Automatically cleans up unused signals when the last reference goes out of scope. This namespace implementation provides similar behavior to Blinker <= 1.2. .. deprecated:: 1.3 Will be removed in Blinker 1.9. .. versionadded:: 1.3 """ def __init__(self) -> None: warnings.warn( "'WeakNamespace' is deprecated and will be removed in Blinker 1.9." " Use 'Namespace' instead.", DeprecationWarning, stacklevel=2, ) super().__init__() def signal(self, name: str, doc: str | None = None) -> NamedSignal: """Return the :class:`NamedSignal` for the given ``name``, creating it if required. Repeated calls with the same name return the same signal. :param name: The name of the signal. :param doc: The docstring of the signal. """ if name not in self: self[name] = NamedSignal(name, doc) return self[name] # type: ignore[no-any-return] default_namespace: Namespace = Namespace() """A default :class:`Namespace` for creating named signals. :func:`signal` creates a :class:`NamedSignal` in this namespace. """ signal: PNamespaceSignal = default_namespace.signal """Return a :class:`NamedSignal` in :data:`default_namespace` with the given ``name``, creating it if required. Repeated calls with the same name return the same signal. """ def __getattr__(name: str) -> t.Any: if name == "receiver_connected": warnings.warn( "The global 'receiver_connected' signal is deprecated and will be" " removed in Blinker 1.9. Use 'Signal.receiver_connected' and" " 'Signal.receiver_disconnected' instead.", DeprecationWarning, stacklevel=2, ) return _receiver_connected if name == "WeakNamespace": warnings.warn( "'WeakNamespace' is deprecated and will be removed in Blinker 1.9." " Use 'Namespace' instead.", DeprecationWarning, stacklevel=2, ) return _WeakNamespace raise AttributeError(name)