Treat an empty application/json body as {} in parse_form

fasthtml/core.py

@@ -154,16 +154,16 @@ def form2dict(form: FormData) -> dict:
 
 # %% ../nbs/api/00_core.ipynb #42c9cea0
 async def parse_form(req: Request) -> FormData:
-    "Starlette errors on empty multipart forms, so this checks for that situation"
+    "Starlette errors on empty multipart/json forms, so this checks for that situation"
     ctype = req.headers.get("Content-Type", "")
     if ctype.startswith("multipart/form-data"):
         try: boundary = ctype.split("boundary=")[1].strip()
         except IndexError: raise HTTPException(400, "Invalid form-data: no boundary")
         if int(req.headers.get("Content-Length", "0")) <= len(boundary) + 6: return FormData()
         return await req.form()
-    await req.body()  # Cache body for non-multipart request types
-    return await req.json() if ctype == 'application/json' else await req.form()
-
+    body = await req.body()  # Cache body for non-multipart request types
+    if ctype == 'application/json': return await req.json() if body else {}
+    return await req.form()
 
 # %% ../nbs/api/00_core.ipynb #0caedd04
 async def _from_body(conn, p, data):

nbs/api/00_core.ipynb

@@ -595,15 +595,16 @@
    "source": [
     "#| export\n",
     "async def parse_form(req: Request) -> FormData:\n",
-    "    \"Starlette errors on empty multipart forms, so this checks for that situation\"\n",
+    "    \"Starlette errors on empty multipart/json forms, so this checks for that situation\"\n",
     "    ctype = req.headers.get(\"Content-Type\", \"\")\n",
     "    if ctype.startswith(\"multipart/form-data\"):\n",
     "        try: boundary = ctype.split(\"boundary=\")[1].strip()\n",
     "        except IndexError: raise HTTPException(400, \"Invalid form-data: no boundary\")\n",
     "        if int(req.headers.get(\"Content-Length\", \"0\")) <= len(boundary) + 6: return FormData()\n",
     "        return await req.form()\n",
-    "    await req.body()  # Cache body for non-multipart request types\n",
-    "    return await req.json() if ctype == 'application/json' else await req.form()\n"
+    "    body = await req.body()  # Cache body for non-multipart request types\n",
+    "    if ctype == 'application/json': return await req.json() if body else {}\n",
+    "    return await req.form()"
    ]
   },
   {
@@ -734,6 +735,23 @@
     "print(response.json())"
    ]
   },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "301e06eb",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "# An empty `application/json` body yields `{}` (like the empty-multipart guard), not a 500\n",
+    "async def _empty_json(req): return JSONResponse(form2dict(await parse_form(req)))\n",
+    "client = TestClient(Starlette(routes=[Route('/', _empty_json, methods=['POST'])]))\n",
+    "res = client.post('/', headers={'content-type':'application/json'})\n",
+    "test_eq(res.status_code, 200)\n",
+    "test_eq(res.json(), {})\n",
+    "res = client.post('/', json={'a':1})          # non-empty json still parses (behavior preserved)\n",
+    "test_eq(res.json(), {'a':1})"
+   ]
+  },
   {
    "cell_type": "code",
    "execution_count": null,