[h3] make send_datagram raise InvalidStreamTypeError

DATAGRAM frames may only be sent on client-initiated bidirectional
streams, raise an exception if `send_push_promise` is called on an
invalid stream ID.

src/aioquic/h3/connection.py

@@ -400,12 +400,19 @@ def send_datagram(self, stream_id: int, data: bytes) -> None:
         """
         Send a datagram for the specified stream.
 
+        If the stream ID is not a client-initiated bidirectional stream, an
+        :class:`~aioquic.h3.exceptions.InvalidStreamTypeError` exception is raised.
+
         :param stream_id: The stream ID.
         :param data: The HTTP/3 datagram payload.
         """
-        assert (
-            stream_id % 4 == 0
-        ), "Datagrams can only be sent for client-initiated bidirectional streams"
+
+        # check stream ID is valid
+        if not stream_is_request_response(stream_id):
+            raise InvalidStreamTypeError(
+                "Datagrams can only be sent for client-initiated bidirectional streams"
+            )
+
         self._quic.send_datagram_frame(encode_uint_var(stream_id // 4) + data)
 
     def send_push_promise(self, stream_id: int, headers: Headers) -> int:

tests/test_webtransport.py

@@ -6,6 +6,7 @@
     HeadersReceived,
     WebTransportStreamDataReceived,
 )
+from aioquic.h3.exceptions import InvalidStreamTypeError
 from aioquic.quic.configuration import QuicConfiguration
 from aioquic.quic.events import DatagramFrameReceived
 
@@ -281,6 +282,10 @@ def test_datagram(self):
             # create session
             session_id = self._make_session(h3_client, h3_server)
 
+            # send datagram on a server-initiated stream
+            with self.assertRaises(InvalidStreamTypeError):
+                h3_client.send_datagram(data=b"foo", stream_id=1)
+
             # send datagram
             h3_client.send_datagram(data=b"foo", stream_id=session_id)