Add a send_async method to the Signal

This allows for signals to send to coroutine receivers by awaiting
them. The _async_wrapper and _sync_wrapper allows for conversion of
sync and async receivers as required if defined. If not defined a
runtime error is raised.

The wrappers are used to avoid any direct tie into asyncio, trio,
greenbacks, asgiref, or other specific async implementation.

1 files changed, 27 insertions, 0 deletions

diff --git a/tests/test_signals.py b/tests/test_signals.py
index 4f1114d..1fca3e5 100644
--- a/tests/test_signals.py
+++ b/tests/test_signals.py
@@ -332,6 +332,33 @@ def test_strong_receiver():
     assert [id(fn) for fn in sig.receivers.values()] == [fn_id]
 
 
+async def test_async_receiver():
+    sentinel = []
+
+    async def received_async(sender):
+        sentinel.append(sender)
+
+    def received(sender):
+        sentinel.append(sender)
+
+    def wrapper(func):
+
+        async def inner(*args, **kwargs):
+            func(*args, **kwargs)
+
+        return inner
+
+    sig = blinker.Signal()
+    sig.connect(received)
+    sig.connect(received_async)
+
+    await sig.send_async(_sync_wrapper=wrapper)
+    assert len(sentinel) == 2
+
+    with pytest.raises(RuntimeError):
+        sig.send()
+
+
 def test_instancemethod_receiver():
     sentinel = []