Add Provider.async_() method + tests

src/dependency_injector/providers.pyx

@@ -277,6 +277,23 @@ cdef class Provider(object):
             self.__overridden = tuple()
             self.__last_overriding = None
 
+    def async_(self, *args, **kwargs):
+        """Return provided object asynchronously.
+
+        This method is a synonym of __call__().
+        It provides typing stubs for correct type checking with
+        `await` expression:
+
+        .. code-block:: python
+
+            database_provider: Provider[DatabaseConnection] = Resource(init_db_async)
+
+            async def main():
+                db: DatabaseConnection = await database_provider.async_()
+                ...
+        """
+        return self.__call__(*args, **kwargs)
+
     def delegate(self):
         """Return provider's delegate.
 

tests/unit/providers/test_async_py36.py

@@ -707,3 +707,35 @@ class TestAsyncModeApi(unittest.TestCase):
         self.assertFalse(self.provider.is_async_mode_enabled())
         self.assertFalse(self.provider.is_async_mode_disabled())
         self.assertTrue(self.provider.is_async_mode_undefined())
+
+
+class AsyncTypingStubTests(AsyncTestCase):
+
+    def test_async_(self):
+        container = Container()
+
+        client1 = self._run(container.client.async_())
+        client2 = self._run(container.client.async_())
+
+        self.assertIsInstance(client1, Client)
+        self.assertIs(client1.resource1, RESOURCE1)
+        self.assertIs(client1.resource2, RESOURCE2)
+
+        self.assertIsInstance(client2, Client)
+        self.assertIs(client2.resource1, RESOURCE1)
+        self.assertIs(client2.resource2, RESOURCE2)
+
+        service1 = self._run(container.service.async_())
+        service2 = self._run(container.service.async_())
+
+        self.assertIsInstance(service1, Service)
+        self.assertIsInstance(service1.client, Client)
+        self.assertIs(service1.client.resource1, RESOURCE1)
+        self.assertIs(service1.client.resource2, RESOURCE2)
+
+        self.assertIsInstance(service2, Service)
+        self.assertIsInstance(service2.client, Client)
+        self.assertIs(service2.client.resource1, RESOURCE1)
+        self.assertIs(service2.client.resource2, RESOURCE2)
+
+        self.assertIsNot(service1.client, service2.client)