Merge pull request #18 from jek/feature/send-async

Adds Signal.send_async for asyncio

Author: @jek

CHANGES

@@ -10,6 +10,8 @@ Not yet released.
 - Verified Python 3.7 support (no changes needed).
 - Verified Python 3.6 support (no changes needed).
 - Verified Python 3.5 support (no changes needed).
+- Added Signal.send_async, dispatching to an arbitrary mix of connected
+  coroutines and receiver functions.
 
 Version 1.4
 -----------

README.md

@@ -9,6 +9,9 @@ interested parties to subscribe to events, or "signals".
 Signal receivers can subscribe to specific senders or receive signals
 sent by any sender.
 
+It supports dispatching to an arbitrary mix of connected
+coroutines and receiver functions.
+
 ```python
 >>> from blinker import signal
 >>> started = signal('round-started')

blinker/__init__.py

@@ -20,3 +20,8 @@
 
 
 __version__ = '1.5dev'
+
+try:
+    import blinker._async
+except (ImportError, SyntaxError):
+    pass

blinker/_async.py

@@ -0,0 +1,28 @@
+import asyncio
+
+from blinker.base import Signal
+
+
+try:
+    schedule = asyncio.create_task
+except AttributeError:
+    schedule = asyncio.ensure_future
+
+
+@asyncio.coroutine
+def _wrap_plain_value(value):
+    """Pass through a coroutine *value* or wrap a plain value."""
+    if asyncio.iscoroutine(value):
+        value = yield from value
+    return value
+
+
+def send_async(self, *sender, **kwargs):
+    return [(receiver, schedule(_wrap_plain_value(value)))
+            for receiver, value
+            in self.send(*sender, **kwargs)]
+
+
+send_async.__doc__ = Signal.send_async.__doc__
+Signal.send_async = send_async
+

blinker/base.py

@@ -271,6 +271,17 @@ def send(self, *sender, **kwargs):
         return [(receiver, receiver(sender, **kwargs))
                 for receiver in self.receivers_for(sender)]
 
+    def send_async(self, *sender, **kwargs):
+        """Send and collect results from connected functions and coroutines.
+
+        As `Signal.send`, but also schedules any coroutines connected to the
+        signal, and uniformly presents all receiver return values as futures,
+        even if one or more receivers are regular functions.
+
+        Available only if asyncio and `yield from` are present.
+        """
+        raise NotImplementedError("asyncio support unavailable")
+
     def has_receivers_for(self, sender):
         """True if there is probably a receiver for *sender*.
 

docs/source/index.rst

@@ -14,6 +14,7 @@ The core of Blinker is quite small but provides powerful features:
  - sending arbitrary data payloads
  - collecting return values from signal receivers
  - thread safety
+ - coroutines as signal receivers
 
 Blinker was written by Jason Kirtand and is provided under the MIT
 License. The library supports Python 2.7 and Python 3.5 or later;
@@ -94,6 +95,35 @@ notifications being sent, and these no-op sends are optimized to be as
 inexpensive as possible.
 
 
+Async support
+-------------
+
+Send a signal asynchronously to coroutine receivers.
+
+  >>> async def receiver_a(sender):
+  ...     return 'value a'
+  ...
+  >>> async def receiver_b(sender):
+  ...     return 'value b'
+  ...
+  >>> ready = signal('ready')
+  >>> ready.connect(receiver_a)
+  >>> ready.connect(receiver_b)
+  ...
+  >>> async def collect():
+  ...     return ready.send_async('sender')
+  ...
+  >>> loop = asyncio.get_event_loop()
+  >>> results = loop.run_until_complete(collect())
+  >>> len(results)
+  2
+  >>> [v.result() for r, v in results][0]
+  value a
+
+Dispatching to an arbitrary mix of connected
+coroutines and receiver functions is supported.
+
+
 Subscribing to Specific Senders
 -------------------------------
 

tests/_test_async.py

@@ -0,0 +1,43 @@
+import asyncio
+
+import blinker
+
+
+def test_send_async():
+    calls = []
+
+    @asyncio.coroutine
+    def receiver_a(sender):
+        calls.append(receiver_a)
+        return 'value a'
+
+    @asyncio.coroutine
+    def receiver_b(sender):
+        calls.append(receiver_b)
+        return 'value b'
+
+    def receiver_c(sender):
+        calls.append(receiver_c)
+        return 'value c'
+
+    sig = blinker.Signal()
+    sig.connect(receiver_a)
+    sig.connect(receiver_b)
+    sig.connect(receiver_c)
+
+    @asyncio.coroutine
+    def collect():
+        return sig.send_async()
+
+    loop = asyncio.get_event_loop()
+    results = loop.run_until_complete(collect())
+
+    expected = {
+        receiver_a: 'value a',
+        receiver_b: 'value b',
+        receiver_c: 'value c',
+        }
+
+    assert set(calls) == set(expected.keys())
+    collected_results = {v.result() for r, v in results}
+    assert collected_results == set(expected.values())

tests/test_signals.py

@@ -10,6 +10,11 @@
 jython = sys.platform.startswith('java')
 pypy = hasattr(sys, 'pypy_version_info')
 
+try:
+    from _test_async import test_send_async
+except (SyntaxError, ImportError):
+    pass
+
 
 def collect_acyclic_refs():
     # cpython releases these immediately without a collection