Add Async classes to typehinting.

Author: Roy Williams

src/test_typing.py

@@ -1,3 +1,4 @@
+import asyncio
 import pickle
 import re
 import sys
@@ -959,6 +960,34 @@ def blah():
                 pass
 
 
+T_a = TypeVar('T')
+
+
+class AwaitableWrapper(typing.Awaitable[T_a]):
+    def __init__(self, value):
+        self.value = value
+
+    def __await__(self) -> typing.Iterator[T_a]:
+        yield
+        return self.value
+
+
+class AsyncIteratorWrapper(typing.AsyncIterator[T_a]):
+    def __init__(self, value: typing.Iterable[T_a]):
+        self.value = value
+
+    def __aiter__(self) -> typing.AsyncIterator[T_a]:
+        return self
+
+    @asyncio.coroutine
+    def __anext__(self) -> T_a:
+        data = yield from self.value
+        if data:
+            return data
+        else:
+            raise StopAsyncIteration
+
+
 class CollectionsAbcTests(TestCase):
 
     def test_hashable(self):
@@ -983,6 +1012,35 @@ def test_iterator(self):
         assert isinstance(it, typing.Iterator[int])
         assert not isinstance(42, typing.Iterator)
 
+    def test_awaitable(self):
+        async def foo() -> typing.Awaitable[int]:
+            return await AwaitableWrapper(42)
+        g = foo()
+        assert issubclass(type(g), typing.Awaitable[int])
+        assert isinstance(g, typing.Awaitable)
+        assert not isinstance(foo, typing.Awaitable)
+        assert issubclass(typing.Awaitable[Manager],
+                          typing.Awaitable[Employee])
+        assert not issubclass(typing.Awaitable[Employee],
+                              typing.Awaitable[Manager])
+
+    def test_async_iterable(self):
+        base_it = range(10)  # type: Iterator[int]
+        it = AsyncIteratorWrapper(base_it)
+        assert isinstance(it, typing.AsyncIterable)
+        assert isinstance(it, typing.AsyncIterable)
+        assert issubclass(typing.AsyncIterable[Manager],
+                          typing.AsyncIterable[Employee])
+        assert not isinstance(42, typing.AsyncIterable)
+
+    def test_async_iterator(self):
+        base_it = range(10)  # type: Iterator[int]
+        it = AsyncIteratorWrapper(base_it)
+        assert isinstance(it, typing.AsyncIterator)
+        assert issubclass(typing.AsyncIterator[Manager],
+                          typing.AsyncIterator[Employee])
+        assert not isinstance(42, typing.AsyncIterator)
+
     def test_sized(self):
         assert isinstance([], typing.Sized)
         assert not isinstance(42, typing.Sized)

src/typing.py

@@ -28,6 +28,9 @@
 
     # ABCs (from collections.abc).
     'AbstractSet',  # collections.abc.Set.
+    'Awaitable',
+    'AsyncIterator',
+    'AsyncIterable',
     'ByteString',
     'Container',
     'Hashable',
@@ -1261,6 +1264,18 @@ class _Protocol(metaclass=_ProtocolMeta):
 Hashable = collections_abc.Hashable  # Not generic.
 
 
+class Awaitable(Generic[T_co], extra=collections_abc.Awaitable):
+    __slots__ = ()
+
+
+class AsyncIterable(Generic[T_co], extra=collections_abc.AsyncIterable):
+    __slots__ = ()
+
+
+class AsyncIterator(AsyncIterable[T_co], extra=collections_abc.AsyncIterator):
+    __slots__ = ()
+
+
 class Iterable(Generic[T_co], extra=collections_abc.Iterable):
     __slots__ = ()