Fix StreamingResponse handling in _resp

Author: kenfj

fasthtml/core.py

@@ -449,8 +449,8 @@ def _resp(req, resp, cls=empty, status_code=200):
     if cls in (Any,FT): cls=empty
     if isinstance(resp, FileResponse) and not os.path.exists(resp.path): raise HTTPException(404, resp.path)
     resp,kw = _part_resp(req, resp)
-    if cls is not empty: return cls(resp, status_code=status_code, **kw)
     if isinstance(resp, Response): return resp
+    if cls is not empty: return cls(resp, status_code=status_code, **kw)
     if _is_ft_resp(resp):
         cts = _xt_cts(req, resp)
         return HTMLResponse(cts, status_code=status_code, **kw)

nbs/api/00_core.ipynb

@@ -131,7 +131,7 @@
     {
      "data": {
       "text/plain": [
-       "datetime.datetime(2025, 10, 27, 14, 0)"
+       "datetime.datetime(2025, 11, 6, 14, 0)"
       ]
      },
      "execution_count": null,
@@ -645,6 +645,14 @@
    "id": "4b36f60b",
    "metadata": {},
    "outputs": [
+    {
+     "name": "stderr",
+     "output_type": "stream",
+     "text": [
+      "/var/folders/mp/wqhpw2456_79dcf12s7696m80000gn/T/ipykernel_76187/1644855005.py:8: DeprecationWarning: 'asyncio.iscoroutinefunction' is deprecated and slated for removal in Python 3.16; use inspect.iscoroutinefunction() instead\n",
+      "  if ctor: return await ctor(data, req) if asyncio.iscoroutinefunction(ctor) else ctor(data, req)\n"
+     ]
+    },
     {
      "data": {
       "text/plain": [
@@ -1366,8 +1374,8 @@
     "    if cls in (Any,FT): cls=empty\n",
     "    if isinstance(resp, FileResponse) and not os.path.exists(resp.path): raise HTTPException(404, resp.path)\n",
     "    resp,kw = _part_resp(req, resp)\n",
-    "    if cls is not empty: return cls(resp, status_code=status_code, **kw)\n",
     "    if isinstance(resp, Response): return resp\n",
+    "    if cls is not empty: return cls(resp, status_code=status_code, **kw)\n",
     "    if _is_ft_resp(resp):\n",
     "        cts = _xt_cts(req, resp)\n",
     "        return HTMLResponse(cts, status_code=status_code, **kw)\n",
@@ -1379,6 +1387,44 @@
     "    return cls(resp, status_code=status_code, **kw)"
    ]
   },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "e2e4a9c2",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "# Test for StreamingResponse behavior\n",
+    "# Before the fix, the following error occurs:\n",
+    "# TypeError: 'StreamingResponse' object is not iterable\n",
+    "import asyncio\n",
+    "from fasthtml.common import fast_app\n",
+    "from starlette.applications import Starlette\n",
+    "from starlette.responses import StreamingResponse\n",
+    "from starlette.testclient import TestClient\n",
+    "from starlette.routing import Route\n",
+    "\n",
+    "def simple_message_generator():\n",
+    "    async def gen():\n",
+    "        for i in range(3):\n",
+    "            yield f\"data: message {i}\\n\\n\"\n",
+    "            await asyncio.sleep(0.01)\n",
+    "    return gen()\n",
+    "\n",
+    "app, rt = fast_app()\n",
+    "\n",
+    "@rt(\"/sse/notify\", methods=[\"GET\"])\n",
+    "async def get_sse_notify(req) -> StreamingResponse:\n",
+    "    return EventStream(simple_message_generator())\n",
+    "\n",
+    "client = TestClient(app)\n",
+    "response = client.get('/sse/notify')\n",
+    "\n",
+    "assert response.status_code == 200\n",
+    "assert response.headers['content-type'].startswith('text/event-stream')\n",
+    "assert \"message\" in response.text"
+   ]
+  },
   {
    "cell_type": "code",
    "execution_count": null,
@@ -2888,13 +2934,13 @@
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "Set to 2025-10-27 07:27:07.025956\n"
+      "Set to 2025-11-06 21:42:16.392974\n"
      ]
     },
     {
      "data": {
       "text/plain": [
-       "'Session time: 2025-10-27 07:27:07.025956'"
+       "'Session time: 2025-11-06 21:42:16.392974'"
       ]
      },
      "execution_count": null,
@@ -3511,7 +3557,7 @@
     {
      "data": {
       "text/plain": [
-       "'Cookie was set at time 07:28:31.264910'"
+       "'Cookie was set at time 21:42:17.129483'"
       ]
      },
      "execution_count": null,