fix 793: allow custom async iterator

starlette/responses.py

@@ -1,6 +1,5 @@
 import hashlib
 import http.cookies
-import inspect
 import json
 import os
 import stat
@@ -204,7 +203,7 @@ def __init__(
         media_type: str = None,
         background: BackgroundTask = None,
     ) -> None:
-        if inspect.isasyncgen(content):
+        if isinstance(content, typing.AsyncIterable):
             self.body_iterator = content
         else:
             self.body_iterator = iterate_in_threadpool(content)

tests/test_responses.py

@@ -269,3 +269,39 @@ def test_head_method():
     client = TestClient(app)
     response = client.head("/")
     assert response.text == ""
+
+def test_sync_custom_streaming_response():
+    async def app(scope, receive, send):
+        class CustomAsyncGenerator:
+            def __init__(self):
+                self._called = 0
+
+            def __aiter__(self):
+                return self
+
+            async def __anext__(self):
+                if self._called == 5:
+                    raise StopAsyncIteration()
+                self._called += 1
+                return str(self._called)
+
+        response = StreamingResponse(CustomAsyncGenerator(), media_type="text/plain")
+        await response(scope, receive, send)
+
+    client = TestClient(app)
+    response = client.get("/")
+    assert response.text == "12345"
+
+def test_sync_custom_streaming_response_no_anext():
+    async def app(scope, receive, send):
+        class CustomAsyncGenerator:
+            async def __aiter__(self):
+                for i in range(5):
+                    yield str(i + 1)
+
+        response = StreamingResponse(CustomAsyncGenerator(), media_type="text/plain")
+        await response(scope, receive, send)
+
+    client = TestClient(app)
+    response = client.get("/")
+    assert response.text == "12345"