Convert signal receiver into a context manager

fimfarchive/signals.py

@@ -30,6 +30,10 @@ __all__ = (
     'SignalBinder',
     'SignalSender',
     'SignalReceiver',
+    'find_related',
+    'find_sources',
+    'find_targets',
+    'find_matches',
 )
 
 
@@ -125,25 +129,22 @@ class SignalBinder:
 
 class SignalSender:
     """
-    Automatically binds signals on init.
+    Automatically binds unbound signals on init.
     """
 
     def __init__(self):
         """
         Constructor.
         """
-        sources = {
-            k: v for k, v in vars(type(self)).items()
-            if k.startswith('on_') and isinstance(v, Signal)
-        }
-
-        for k, v in sources.items():
-            setattr(self, k, SignalBinder(v, self))
+        for key, source in find_sources(self):
+            if not isinstance(source, SignalBinder):
+                binding = SignalBinder(source, self)
+                setattr(self, key, binding)
 
 
 class SignalReceiver:
     """
-    Automatically connects signals on init.
+    Automatically connects signals on enter.
     """
 
     def __init__(self, sender):
@@ -153,19 +154,55 @@ class SignalReceiver:
         Args:
             sender: Object to connect to.
         """
-        sources = {
-            k for k, v in vars(type(sender)).items()
-            if k.startswith('on_') and isinstance(v, Signal)
-        }
+        self.sender = sender
 
-        targets = {
-            k for k, v in vars(type(self)).items()
-            if k.startswith('on_') and callable(v)
-        }
+    def __enter__(self):
+        for key, source, target in find_matches(self.sender, self):
+            source.connect(target, sender=self.sender)
 
-        connect = sources.intersection(targets)
+        return self
 
-        for key in connect:
-            method = getattr(self, key)
-            signal = getattr(sender, key)
-            signal.connect(method, sender=sender)
+    def __exit__(self, *args):
+        for key, source, target in find_matches(self.sender, self):
+            source.disconnect(target, sender=self.sender)
+
+
+def find_related(obj):
+    """
+    Yields all source or target candidates.
+    """
+    for key in dir(obj):
+        if key.startswith('on_'):
+            yield key, getattr(obj, key)
+
+
+def find_sources(sender):
+    """
+    Yields all source signals in a sender.
+    """
+    for key, value in find_related(sender):
+        connect = getattr(value, 'connect', None)
+        disconnect = getattr(value, 'disconnect', None)
+
+        if callable(connect) and callable(disconnect):
+            yield key, value
+
+
+def find_targets(receiver):
+    """
+    Yields all target methods in a receiver.
+    """
+    for key, value in find_related(receiver):
+        if callable(value):
+            yield key, value
+
+
+def find_matches(sender, receiver):
+    """
+    Yields all matching signal connections.
+    """
+    sources = dict(find_sources(sender))
+    targets = dict(find_targets(receiver))
+
+    for key in sources.keys() & targets.keys():
+        yield key, sources[key], targets[key]

tests/test_signals.py

@@ -69,12 +69,13 @@ def sender(signal):
 @pytest.fixture
 def receiver(sender):
     """
-    Returns a signal receiver instance.
+    Returns a connected signal receiver intance.
     """
     class Receiver(SignalReceiver):
         on_signal = Mock('on_signal')
 
-    return Receiver(sender)
+    with Receiver(sender) as receiver:
+        yield receiver
 
 
 @pytest.fixture
@@ -182,7 +183,7 @@ class TestSignalReceiver:
 
     def test_send(self, params, sender, receiver):
         """
-        Tests receiver recives emitted singal.
+        Tests receiver receives emitted signal.
         """
         sender.on_signal(*params.values())
         receiver.on_signal.assert_called_once_with(sender, **params)