Move to src/ layout

4 files changed, 798 insertions, 0 deletions

diff --git a/src/blinker/__init__.py b/src/blinker/__init__.py
new file mode 100644
index 0000000..5ec9d0b
--- /dev/null
+++ b/src/blinker/__init__.py
@@ -0,0 +1,20 @@
+from blinker.base import ANY
+from blinker.base import NamedSignal
+from blinker.base import Namespace
+from blinker.base import receiver_connected
+from blinker.base import Signal
+from blinker.base import signal
+from blinker.base import WeakNamespace
+
+__all__ = [
+    "ANY",
+    "NamedSignal",
+    "Namespace",
+    "Signal",
+    "WeakNamespace",
+    "receiver_connected",
+    "signal",
+]
+
+
+__version__ = "1.5"
diff --git a/src/blinker/_saferef.py b/src/blinker/_saferef.py
new file mode 100644
index 0000000..8848dea
--- /dev/null
+++ b/src/blinker/_saferef.py
@@ -0,0 +1,228 @@
+# extracted from Louie, http://pylouie.org/
+# updated for Python 3
+#
+# Copyright (c) 2006 Patrick K. O'Brien, Mike C. Fletcher,
+#                    Matthew R. Scott
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+#       notice, this list of conditions and the following disclaimer.
+#
+#     * Redistributions in binary form must reproduce the above
+#       copyright notice, this list of conditions and the following
+#       disclaimer in the documentation and/or other materials provided
+#       with the distribution.
+#
+#     * Neither the name of the <ORGANIZATION> nor the names of its
+#       contributors may be used to endorse or promote products derived
+#       from this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#
+"""Refactored 'safe reference from dispatcher.py"""
+import operator
+import sys
+import traceback
+import weakref
+
+
+get_self = operator.attrgetter("__self__")
+get_func = operator.attrgetter("__func__")
+
+
+def safe_ref(target, on_delete=None):
+    """Return a *safe* weak reference to a callable target.
+
+    - ``target``: The object to be weakly referenced, if it's a bound
+      method reference, will create a BoundMethodWeakref, otherwise
+      creates a simple weakref.
+
+    - ``on_delete``: If provided, will have a hard reference stored to
+      the callable to be called after the safe reference goes out of
+      scope with the reference object, (either a weakref or a
+      BoundMethodWeakref) as argument.
+    """
+    try:
+        im_self = get_self(target)
+    except AttributeError:
+        if callable(on_delete):
+            return weakref.ref(target, on_delete)
+        else:
+            return weakref.ref(target)
+    else:
+        if im_self is not None:
+            # Turn a bound method into a BoundMethodWeakref instance.
+            # Keep track of these instances for lookup by disconnect().
+            assert hasattr(target, "im_func") or hasattr(target, "__func__"), (
+                f"safe_ref target {target!r} has im_self, but no im_func, "
+                "don't know how to create reference"
+            )
+            reference = BoundMethodWeakref(target=target, on_delete=on_delete)
+            return reference
+
+
+class BoundMethodWeakref:
+    """'Safe' and reusable weak references to instance methods.
+
+    BoundMethodWeakref objects provide a mechanism for referencing a
+    bound method without requiring that the method object itself
+    (which is normally a transient object) is kept alive.  Instead,
+    the BoundMethodWeakref object keeps weak references to both the
+    object and the function which together define the instance method.
+
+    Attributes:
+
+    - ``key``: The identity key for the reference, calculated by the
+      class's calculate_key method applied to the target instance method.
+
+    - ``deletion_methods``: Sequence of callable objects taking single
+      argument, a reference to this object which will be called when
+      *either* the target object or target function is garbage
+      collected (i.e. when this object becomes invalid).  These are
+      specified as the on_delete parameters of safe_ref calls.
+
+    - ``weak_self``: Weak reference to the target object.
+
+    - ``weak_func``: Weak reference to the target function.
+
+    Class Attributes:
+
+    - ``_all_instances``: Class attribute pointing to all live
+      BoundMethodWeakref objects indexed by the class's
+      calculate_key(target) method applied to the target objects.
+      This weak value dictionary is used to short-circuit creation so
+      that multiple references to the same (object, function) pair
+      produce the same BoundMethodWeakref instance.
+    """
+
+    _all_instances = weakref.WeakValueDictionary()
+
+    def __new__(cls, target, on_delete=None, *arguments, **named):
+        """Create new instance or return current instance.
+
+        Basically this method of construction allows us to
+        short-circuit creation of references to already-referenced
+        instance methods.  The key corresponding to the target is
+        calculated, and if there is already an existing reference,
+        that is returned, with its deletion_methods attribute updated.
+        Otherwise the new instance is created and registered in the
+        table of already-referenced methods.
+        """
+        key = cls.calculate_key(target)
+        current = cls._all_instances.get(key)
+        if current is not None:
+            current.deletion_methods.append(on_delete)
+            return current
+        else:
+            base = super().__new__(cls)
+            cls._all_instances[key] = base
+            base.__init__(target, on_delete, *arguments, **named)
+            return base
+
+    def __init__(self, target, on_delete=None):
+        """Return a weak-reference-like instance for a bound method.
+
+        - ``target``: The instance-method target for the weak reference,
+          must have im_self and im_func attributes and be
+          reconstructable via the following, which is true of built-in
+          instance methods::
+
+            target.im_func.__get__( target.im_self )
+
+        - ``on_delete``: Optional callback which will be called when
+          this weak reference ceases to be valid (i.e. either the
+          object or the function is garbage collected).  Should take a
+          single argument, which will be passed a pointer to this
+          object.
+        """
+
+        def remove(weak, self=self):
+            """Set self.isDead to True when method or instance is destroyed."""
+            methods = self.deletion_methods[:]
+            del self.deletion_methods[:]
+            try:
+                del self.__class__._all_instances[self.key]
+            except KeyError:
+                pass
+            for function in methods:
+                try:
+                    if callable(function):
+                        function(self)
+                except Exception:
+                    try:
+                        traceback.print_exc()
+                    except AttributeError:
+                        e = sys.exc_info()[1]
+                        print(
+                            f"Exception during saferef {self} "
+                            f"cleanup function {function}: {e}"
+                        )
+
+        self.deletion_methods = [on_delete]
+        self.key = self.calculate_key(target)
+        im_self = get_self(target)
+        im_func = get_func(target)
+        self.weak_self = weakref.ref(im_self, remove)
+        self.weak_func = weakref.ref(im_func, remove)
+        self.self_name = str(im_self)
+        self.func_name = str(im_func.__name__)
+
+    def calculate_key(cls, target):
+        """Calculate the reference key for this reference.
+
+        Currently this is a two-tuple of the id()'s of the target
+        object and the target function respectively.
+        """
+        return (id(get_self(target)), id(get_func(target)))
+
+    calculate_key = classmethod(calculate_key)
+
+    def __str__(self):
+        """Give a friendly representation of the object."""
+        return "{}({}.{})".format(
+            self.__class__.__name__,
+            self.self_name,
+            self.func_name,
+        )
+
+    __repr__ = __str__
+
+    def __nonzero__(self):
+        """Whether we are still a valid reference."""
+        return self() is not None
+
+    def __cmp__(self, other):
+        """Compare with another reference."""
+        if not isinstance(other, self.__class__):
+            return cmp(self.__class__, type(other))
+        return cmp(self.key, other.key)
+
+    def __call__(self):
+        """Return a strong reference to the bound method.
+
+        If the target cannot be retrieved, then will return None,
+        otherwise returns a bound instance method for our object and
+        function.
+
+        Note: You may call this method any number of times, as it does
+        not invalidate the reference.
+        """
+        target = self.weak_self()
+        if target is not None:
+            function = self.weak_func()
+            if function is not None:
+                return function.__get__(target)
+        return None
diff --git a/src/blinker/_utilities.py b/src/blinker/_utilities.py
new file mode 100644
index 0000000..d64d8e8
--- /dev/null
+++ b/src/blinker/_utilities.py
@@ -0,0 +1,95 @@
+from weakref import ref
+
+from blinker._saferef import BoundMethodWeakref
+
+
+class _symbol:
+    def __init__(self, name):
+        """Construct a new named symbol."""
+        self.__name__ = self.name = name
+
+    def __reduce__(self):
+        return symbol, (self.name,)
+
+    def __repr__(self):
+        return self.name
+
+
+_symbol.__name__ = "symbol"
+
+
+class symbol:
+    """A constant symbol.
+
+    >>> symbol('foo') is symbol('foo')
+    True
+    >>> symbol('foo')
+    foo
+
+    A slight refinement of the MAGICCOOKIE=object() pattern.  The primary
+    advantage of symbol() is its repr().  They are also singletons.
+
+    Repeated calls of symbol('name') will all return the same instance.
+
+    """
+
+    symbols = {}
+
+    def __new__(cls, name):
+        try:
+            return cls.symbols[name]
+        except KeyError:
+            return cls.symbols.setdefault(name, _symbol(name))
+
+
+def hashable_identity(obj):
+    if hasattr(obj, "__func__"):
+        return (id(obj.__func__), id(obj.__self__))
+    elif hasattr(obj, "im_func"):
+        return (id(obj.im_func), id(obj.im_self))
+    elif isinstance(obj, str):
+        return obj
+    else:
+        return id(obj)
+
+
+WeakTypes = (ref, BoundMethodWeakref)
+
+
+class annotatable_weakref(ref):
+    """A weakref.ref that supports custom instance attributes."""
+
+
+def reference(object, callback=None, **annotations):
+    """Return an annotated weak ref."""
+    if callable(object):
+        weak = callable_reference(object, callback)
+    else:
+        weak = annotatable_weakref(object, callback)
+    for key, value in annotations.items():
+        setattr(weak, key, value)
+    return weak
+
+
+def callable_reference(object, callback=None):
+    """Return an annotated weak ref, supporting bound instance methods."""
+    if hasattr(object, "im_self") and object.im_self is not None:
+        return BoundMethodWeakref(target=object, on_delete=callback)
+    elif hasattr(object, "__self__") and object.__self__ is not None:
+        return BoundMethodWeakref(target=object, on_delete=callback)
+    return annotatable_weakref(object, callback)
+
+
+class lazy_property:
+    """A @property that is only evaluated once."""
+
+    def __init__(self, deferred):
+        self._deferred = deferred
+        self.__doc__ = deferred.__doc__
+
+    def __get__(self, obj, cls):
+        if obj is None:
+            return self
+        value = self._deferred(obj)
+        setattr(obj, self._deferred.__name__, value)
+        return value
diff --git a/src/blinker/base.py b/src/blinker/base.py
new file mode 100644
index 0000000..467e0ac
--- /dev/null
+++ b/src/blinker/base.py
@@ -0,0 +1,455 @@
+"""Signals and events.
+
+A small implementation of signals, inspired by a snippet of Django signal
+API client code seen in a blog post.  Signals are first-class objects and
+each manages its own receivers and message emission.
+
+The :func:`signal` function provides singleton behavior for named signals.
+
+"""
+from collections import defaultdict
+from contextlib import contextmanager
+from warnings import warn
+from weakref import WeakValueDictionary
+
+from src.blinker._utilities import hashable_identity
+from src.blinker._utilities import lazy_property
+from src.blinker._utilities import reference
+from src.blinker._utilities import symbol
+from src.blinker._utilities import WeakTypes
+
+
+ANY = symbol("ANY")
+ANY.__doc__ = 'Token for "any sender".'
+ANY_ID = 0
+
+
+class Signal:
+    """A notification emitter."""
+
+    #: An :obj:`ANY` convenience synonym, allows ``Signal.ANY``
+    #: without an additional import.
+    ANY = ANY
+
+    @lazy_property
+    def receiver_connected(self):
+        """Emitted after each :meth:`connect`.
+
+        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.")
+
+    @lazy_property
+    def receiver_disconnected(self):
+        """Emitted after :meth:`disconnect`.
+
+        The sender is the signal instance, and the :meth:`disconnect` arguments
+        are passed through: *receiver* and *sender*.
+
+        Note, this signal is emitted **only** when :meth:`disconnect` is
+        called explicitly.
+
+        The disconnect signal can not be emitted by an automatic disconnect
+        (due to a weakly referenced receiver or sender going out of scope),
+        as the receiver and/or sender instances are no longer available for
+        use at the time this signal would be emitted.
+
+        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=None):
+        """
+        :param doc: optional.  If provided, will be assigned to the signal's
+          __doc__ attribute.
+
+        """
+        if doc:
+            self.__doc__ = doc
+        #: A mapping of connected receivers.
+        #:
+        #: The values of this mapping are not meaningful outside of the
+        #: internal :class:`Signal` implementation, however the boolean value
+        #: of the mapping is useful as an extremely efficient check to see if
+        #: any receivers are connected to the signal.
+        self.receivers = {}
+        self._by_receiver = defaultdict(set)
+        self._by_sender = defaultdict(set)
+        self._weak_senders = {}
+
+    def connect(self, receiver, sender=ANY, weak=True):
+        """Connect *receiver* to signal events sent by *sender*.
+
+        :param receiver: A callable.  Will be invoked by :meth:`send` with
+          `sender=` as a single positional argument and any ``kwargs`` that
+          were provided to a call to :meth:`send`.
+
+        :param sender: Any object or :obj:`ANY`, defaults to ``ANY``.
+          Restricts notifications delivered to *receiver* to only those
+          :meth:`send` emissions sent by *sender*.  If ``ANY``, the receiver
+          will always be notified.  A *receiver* may be connected to
+          multiple *sender* values on the same Signal through multiple calls
+          to :meth:`connect`.
+
+        :param weak: If true, the Signal will hold a weakref to *receiver*
+          and automatically disconnect when *receiver* goes out of scope or
+          is garbage collected.  Defaults to True.
+
+        """
+        receiver_id = hashable_identity(receiver)
+        if weak:
+            receiver_ref = reference(receiver, self._cleanup_receiver)
+            receiver_ref.receiver_id = receiver_id
+        else:
+            receiver_ref = receiver
+        if sender is ANY:
+            sender_id = ANY_ID
+        else:
+            sender_id = hashable_identity(sender)
+
+        self.receivers.setdefault(receiver_id, receiver_ref)
+        self._by_sender[sender_id].add(receiver_id)
+        self._by_receiver[receiver_id].add(sender_id)
+        del receiver_ref
+
+        if sender is not ANY and sender_id not in self._weak_senders:
+            # wire together a cleanup for weakref-able senders
+            try:
+                sender_ref = reference(sender, self._cleanup_sender)
+                sender_ref.sender_id = sender_id
+            except TypeError:
+                pass
+            else:
+                self._weak_senders.setdefault(sender_id, sender_ref)
+                del sender_ref
+
+        # broadcast this connection.  if receivers raise, disconnect.
+        if "receiver_connected" in self.__dict__ and self.receiver_connected.receivers:
+            try:
+                self.receiver_connected.send(
+                    self, receiver=receiver, sender=sender, weak=weak
+                )
+            except:
+                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:
+                self.disconnect(receiver, sender)
+                raise
+        return receiver
+
+    def connect_via(self, sender, weak=False):
+        """Connect the decorated function as a receiver for *sender*.
+
+        :param sender: Any object or :obj:`ANY`.  The decorated function
+          will only receive :meth:`send` emissions sent by *sender*.  If
+          ``ANY``, the receiver will always be notified.  A function may be
+          decorated multiple times with differing *sender* values.
+
+        :param weak: If true, the Signal will hold a weakref to the
+          decorated function and automatically disconnect when *receiver*
+          goes out of scope or is garbage collected.  Unlike
+          :meth:`connect`, this defaults to False.
+
+        The decorated function will be invoked by :meth:`send` with
+          `sender=` as a single positional argument and any ``kwargs`` that
+          were provided to the call to :meth:`send`.
+
+
+        .. versionadded:: 1.1
+
+        """
+
+        def decorator(fn):
+            self.connect(fn, sender, weak)
+            return fn
+
+        return decorator
+
+    @contextmanager
+    def connected_to(self, receiver, sender=ANY):
+        """Execute a block with the signal temporarily connected to *receiver*.
+
+        :param receiver: a receiver callable
+        :param sender: optional, a sender to filter on
+
+        This is a context manager for use in the ``with`` statement.  It can
+        be useful in unit tests.  *receiver* is connected to the signal for
+        the duration of the ``with`` block, and will be disconnected
+        automatically when exiting the block:
+
+        .. code-block:: python
+
+          with on_ready.connected_to(receiver):
+             # do stuff
+             on_ready.send(123)
+
+        .. versionadded:: 1.1
+
+        """
+        self.connect(receiver, sender=sender, weak=False)
+        try:
+            yield None
+        except:
+            self.disconnect(receiver)
+            raise
+        else:
+            self.disconnect(receiver)
+
+    def temporarily_connected_to(self, receiver, sender=ANY):
+        """An alias for :meth:`connected_to`.
+
+        :param receiver: a receiver callable
+        :param sender: optional, a sender to filter on
+
+        .. versionadded:: 0.9
+
+        .. versionchanged:: 1.1
+          Renamed to :meth:`connected_to`.  ``temporarily_connected_to`` was
+          deprecated in 1.2 and will be removed in a subsequent version.
+
+        """
+        warn(
+            "temporarily_connected_to is deprecated; " "use connected_to instead.",
+            DeprecationWarning,
+        )
+        return self.connected_to(receiver, sender)
+
+    def send(self, *sender, **kwargs):
+        """Emit this signal on behalf of *sender*, passing on ``kwargs``.
+
+        Returns a list of 2-tuples, pairing receivers with their return
+        value. The ordering of receiver notification is undefined.
+
+        :param sender: Any object or ``None``.  If omitted, synonymous
+          with ``None``.  Only accepts one positional argument.
+
+        :param kwargs: Data to be sent to receivers.
+        """
+        if not self.receivers:
+            # Ensure correct signature even on no-op sends, disable with -O
+            # for lowest possible cost.
+            if __debug__ and sender and len(sender) > 1:
+                raise TypeError(
+                    "send() accepts only one positional "
+                    "argument, %s given" % len(sender)
+                )
+            return []
+
+        # Using '*sender' rather than 'sender=None' allows 'sender' to be
+        # used as a keyword argument- i.e. it's an invisible name in the
+        # function signature.
+        if len(sender) == 0:
+            sender = None
+        elif len(sender) > 1:
+            raise TypeError(
+                "send() accepts only one positional argument, " "%s given" % len(sender)
+            )
+        else:
+            sender = sender[0]
+        return [
+            (receiver, receiver(sender, **kwargs))
+            for receiver in self.receivers_for(sender)
+        ]
+
+    def has_receivers_for(self, sender):
+        """True if there is probably a receiver for *sender*.
+
+        Performs an optimistic check only.  Does not guarantee that all
+        weakly referenced receivers are still alive.  See
+        :meth:`receivers_for` for a stronger search.
+
+        """
+        if not self.receivers:
+            return False
+        if self._by_sender[ANY_ID]:
+            return True
+        if sender is ANY:
+            return False
+        return hashable_identity(sender) in self._by_sender
+
+    def receivers_for(self, sender):
+        """Iterate all live receivers listening for *sender*."""
+        # TODO: test receivers_for(ANY)
+        if self.receivers:
+            sender_id = hashable_identity(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, WeakTypes):
+                    strong = receiver()
+                    if strong is None:
+                        self._disconnect(receiver_id, ANY_ID)
+                        continue
+                    receiver = strong
+                yield receiver
+
+    def disconnect(self, receiver, sender=ANY):
+        """Disconnect *receiver* from this signal's events.
+
+        :param receiver: a previously :meth:`connected<connect>` callable
+
+        :param sender: a specific sender to disconnect from, or :obj:`ANY`
+          to disconnect from all senders.  Defaults to ``ANY``.
+
+        """
+        if sender is ANY:
+            sender_id = ANY_ID
+        else:
+            sender_id = hashable_identity(sender)
+        receiver_id = hashable_identity(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, sender_id):
+        if sender_id == ANY_ID:
+            if self._by_receiver.pop(receiver_id, False):
+                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 _cleanup_receiver(self, receiver_ref):
+        """Disconnect a receiver from all senders."""
+        self._disconnect(receiver_ref.receiver_id, ANY_ID)
+
+    def _cleanup_sender(self, sender_ref):
+        """Disconnect all receivers from a sender."""
+        sender_id = sender_ref.sender_id
+        assert sender_id != ANY_ID
+        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)
+
+    def _cleanup_bookkeeping(self):
+        """Prune unused sender/receiver bookkeeping. Not threadsafe.
+
+        Connecting & disconnecting leave behind a small amount of bookkeeping
+        for the receiver and sender values. 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 Python process performing dynamic signal routing
+        with high volume- e.g. connecting to function closures, "senders" are
+        all unique object instances, and doing all of this over and over- you
+        may see memory usage will 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 _id, bucket in list(mapping.items()):
+                if not bucket:
+                    mapping.pop(_id, None)
+
+    def _clear_state(self):
+        """Throw away all signal state.  Useful for unit 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
+
+As of 1.2, individual signals have their own private
+:attr:`~Signal.receiver_connected` and
+:attr:`~Signal.receiver_disconnected` signals with a slightly simplified
+call signature.  This global signal is planned to be removed in 1.6.
+
+"""
+)
+
+
+class NamedSignal(Signal):
+    """A named generic notification emitter."""
+
+    def __init__(self, name, doc=None):
+        Signal.__init__(self, doc)
+
+        #: The name of this signal.
+        self.name = name
+
+    def __repr__(self):
+        base = Signal.__repr__(self)
+        return f"{base[:-1]}; {self.name!r}>"
+
+
+class Namespace(dict):
+    """A mapping of signal names to signals."""
+
+    def signal(self, name, doc=None):
+        """Return the :class:`NamedSignal` *name*, creating it if required.
+
+        Repeated calls to this function will return the same signal object.
+
+        """
+        try:
+            return self[name]
+        except KeyError:
+            return self.setdefault(name, NamedSignal(name, doc))
+
+
+class WeakNamespace(WeakValueDictionary):
+    """A weak mapping of signal names to signals.
+
+    Automatically cleans up unused Signals when the last reference goes out
+    of scope.  This namespace implementation exists for a measure of legacy
+    compatibility with Blinker <= 1.2, and may be dropped in the future.
+
+    .. versionadded:: 1.3
+
+    """
+
+    def signal(self, name, doc=None):
+        """Return the :class:`NamedSignal` *name*, creating it if required.
+
+        Repeated calls to this function will return the same signal object.
+
+        """
+        try:
+            return self[name]
+        except KeyError:
+            return self.setdefault(name, NamedSignal(name, doc))
+
+
+signal = Namespace().signal