fix(chat): skip azure async filter events (#2255)

Author: kapis

src/openai/lib/streaming/chat/_completions.py

@@ -113,6 +113,8 @@ def current_completion_snapshot(self) -> ParsedChatCompletionSnapshot:
 
     def __stream__(self) -> Iterator[ChatCompletionStreamEvent[ResponseFormatT]]:
         for sse_event in self._raw_stream:
+            if not _is_valid_chat_completion_chunk_weak(sse_event):
+                continue
             events_to_fire = self._state.handle_chunk(sse_event)
             for event in events_to_fire:
                 yield event
@@ -234,6 +236,8 @@ def current_completion_snapshot(self) -> ParsedChatCompletionSnapshot:
 
     async def __stream__(self) -> AsyncIterator[ChatCompletionStreamEvent[ResponseFormatT]]:
         async for sse_event in self._raw_stream:
+            if not _is_valid_chat_completion_chunk_weak(sse_event):
+                continue
             events_to_fire = self._state.handle_chunk(sse_event)
             for event in events_to_fire:
                 yield event
@@ -753,3 +757,12 @@ def _convert_initial_chunk_into_snapshot(chunk: ChatCompletionChunk) -> ParsedCh
             },
         ),
     )
+
+
+def _is_valid_chat_completion_chunk_weak(sse_event: ChatCompletionChunk) -> bool:
+    # Although the _raw_stream is always supposed to contain only objects adhering to ChatCompletionChunk schema,
+    # this is broken by the Azure OpenAI in case of Asynchronous Filter enabled.
+    # An easy filter is to check for the "object" property:
+    # - should be "chat.completion.chunk" for a ChatCompletionChunk;
+    # - is an empty string for Asynchronous Filter events.
+    return sse_event.object == "chat.completion.chunk"  # type: ignore # pylance reports this as a useless check