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, 37 insertions, 0 deletions

diff --git a/src/blinker/_utilities.py b/src/blinker/_utilities.py
index 68e8422..22beb81 100644
--- a/src/blinker/_utilities.py
+++ b/src/blinker/_utilities.py
@@ -1,3 +1,8 @@
+import asyncio
+import inspect
+import sys
+from functools import partial
+from typing import Any
 from weakref import ref
 
 from blinker._saferef import BoundMethodWeakref
@@ -93,3 +98,35 @@ class lazy_property:
         value = self._deferred(obj)
         setattr(obj, self._deferred.__name__, value)
         return value
+
+
+def is_coroutine_function(func: Any) -> bool:
+    # Python < 3.8 does not correctly determine partially wrapped
+    # coroutine functions are coroutine functions, hence the need for
+    # this to exist. Code taken from CPython.
+    if sys.version_info >= (3, 8):
+        return asyncio.iscoroutinefunction(func)
+    else:
+        # Note that there is something special about the AsyncMock
+        # such that it isn't determined as a coroutine function
+        # without an explicit check.
+        try:
+            from unittest.mock import AsyncMock
+
+            if isinstance(func, AsyncMock):
+                return True
+        except ImportError:
+            # Not testing, no asynctest to import
+            pass
+
+        while inspect.ismethod(func):
+            func = func.__func__
+        while isinstance(func, partial):
+            func = func.func
+        if not inspect.isfunction(func):
+            return False
+        result = bool(func.__code__.co_flags & inspect.CO_COROUTINE)
+        return (
+            result
+            or getattr(func, "_is_coroutine", None) is asyncio.coroutines._is_coroutine
+        )