Added `muted` context manager for temproary switching signal off (#84)

This is useful whilst testing to remove a signal's affects.

Co-authored-by: Michael Elovskikh <wronglink@yandex-team.ru>

3 files changed, 52 insertions, 4 deletions

diff --git a/docs/index.rst b/docs/index.rst
index 92b89ba..9c733bb 100644
--- a/docs/index.rst
+++ b/docs/index.rst
@@ -157,6 +157,19 @@ value``) pairs:
   [(<function receive_data at 0x...>, 'received!')]
 
 
+Muting signals
+--------------
+
+To mute a signal, as may be required when testing, the
+:meth:`~Signal.muted` can be used as a context decorator:
+
+.. code-block:: python
+
+  sig = signal('send-data')
+  with sig.muted():
+       ...
+
+
 Anonymous Signals
 -----------------
 
diff --git a/src/blinker/base.py b/src/blinker/base.py
index 2b87cb9..f80750c 100644
--- a/src/blinker/base.py
+++ b/src/blinker/base.py
@@ -82,6 +82,7 @@ class Signal:
         #: of the mapping is useful as an extremely efficient check to see if
         #: any receivers are connected to the signal.
         self.receivers = {}
+        self.is_muted = False
         self._by_receiver = defaultdict(set)
         self._by_sender = defaultdict(set)
         self._weak_senders = {}
@@ -209,6 +210,19 @@ class Signal:
         else:
             self.disconnect(receiver)
 
+    @contextmanager
+    def muted(self):
+        """Context manager for temporarily disabling signal.
+        Useful for test purposes.
+        """
+        self.is_muted = True
+        try:
+            yield None
+        except Exception as e:
+            raise e
+        finally:
+            self.is_muted = False
+
     def temporarily_connected_to(self, receiver, sender=ANY):
         """An alias for :meth:`connected_to`.
 
@@ -259,10 +273,14 @@ class Signal:
             )
         else:
             sender = sender[0]
-        return [
-            (receiver, receiver(sender, **kwargs))
-            for receiver in self.receivers_for(sender)
-        ]
+
+        if self.is_muted:
+            return []
+        else:
+            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*.
diff --git a/tests/test_signals.py b/tests/test_signals.py
index 0879b5c..e79ff7f 100644
--- a/tests/test_signals.py
+++ b/tests/test_signals.py
@@ -512,6 +512,23 @@ def test_named_blinker():
     assert "squiznart" in repr(sig)
 
 
+def test_mute_signal():
+    sentinel = []
+
+    def received(sender):
+        sentinel.append(sender)
+
+    sig = blinker.Signal()
+    sig.connect(received)
+
+    sig.send(123)
+    assert 123 in sentinel
+
+    with sig.muted():
+        sig.send(456)
+    assert 456 not in sentinel
+
+
 def values_are_empty_sets_(dictionary):
     for val in dictionary.values():
         assert val == set()