[Bugfix] Fix Hermes tool parser when stream interval > 1 (#38168)

Signed-off-by: sfeng33 <4florafeng@gmail.com>

tests/tool_parsers/test_hermes_tool_parser.py

@@ -152,6 +152,175 @@ def test_hermes_parser_streaming(
     }
 
 
+def _simulate_streaming(
+    tokenizer: TokenizerLike,
+    parser: ToolParser,
+    request: ChatCompletionRequest,
+    text: str,
+    stream_interval: int = 1,
+) -> list:
+    """Simulate streaming with a given stream_interval.
+
+    Tokens are batched into chunks of `stream_interval` tokens,
+    mimicking how the output processor delivers them.
+    Returns a list of non-None DeltaMessages.
+    """
+    tokens = tokenizer.encode(text)
+    previous_text = ""
+    delta_messages = []
+    for i in range(0, len(tokens), stream_interval):
+        chunk_ids = tokens[i : i + stream_interval]
+        delta_text = tokenizer.decode(chunk_ids)
+        current_text = previous_text + delta_text
+        delta = parser.extract_tool_calls_streaming(
+            previous_text=previous_text,
+            current_text=current_text,
+            delta_text=delta_text,
+            previous_token_ids=[],
+            current_token_ids=[],
+            delta_token_ids=chunk_ids,
+            request=request,
+        )
+        previous_text = current_text
+        if delta is not None:
+            delta_messages.append(delta)
+    return delta_messages
+
+
+@pytest.mark.parametrize("stream_interval", [2, 3, 5, 8])
+def test_hermes_streaming_tool_call_with_stream_interval(
+    qwen_tokenizer: TokenizerLike,
+    any_chat_request: ChatCompletionRequest,
+    stream_interval: int,
+) -> None:
+    """Tool call streaming must produce correct name + args at any interval."""
+    text = (
+        '<tool_call>{"name": "get_current_temperature", '
+        '"arguments": {"location": "San Francisco", "unit": "celsius"}}'
+        "</tool_call>"
+    )
+    parser = Hermes2ProToolParser(qwen_tokenizer)
+    deltas = _simulate_streaming(
+        qwen_tokenizer, parser, any_chat_request, text, stream_interval
+    )
+
+    # Flatten all DeltaToolCalls across all deltas.
+    tool_deltas = [tc for d in deltas if d.tool_calls for tc in d.tool_calls]
+    assert tool_deltas, "Expected at least one tool call delta"
+    assert tool_deltas[0].function.name == "get_current_temperature"
+
+    # Concatenated arguments must be valid JSON matching the original.
+    args_str = "".join(tc.function.arguments or "" for tc in tool_deltas)
+    assert json.loads(args_str) == {
+        "location": "San Francisco",
+        "unit": "celsius",
+    }
+
+
+@pytest.mark.parametrize("stream_interval", [2, 3, 5, 8])
+def test_hermes_streaming_content_then_tool_call_with_stream_interval(
+    qwen_tokenizer: TokenizerLike,
+    any_chat_request: ChatCompletionRequest,
+    stream_interval: int,
+) -> None:
+    """Content before a tool call must be fully streamed, then tool call."""
+    text = (
+        "Sure, let me check the weather."
+        '<tool_call>{"name": "get_weather", '
+        '"arguments": {"city": "NYC"}}</tool_call>'
+    )
+    parser = Hermes2ProToolParser(qwen_tokenizer)
+    deltas = _simulate_streaming(
+        qwen_tokenizer, parser, any_chat_request, text, stream_interval
+    )
+
+    content_deltas = [d for d in deltas if d.content]
+    tool_deltas = [d for d in deltas if d.tool_calls]
+
+    # Content must reconstruct the prefix.
+    content_str = "".join(d.content for d in content_deltas)
+    assert content_str == "Sure, let me check the weather."
+
+    # Tool call must be correct.
+    tool_calls = [tc for d in tool_deltas for tc in d.tool_calls]
+    assert tool_calls[0].function.name == "get_weather"
+    args_str = "".join(tc.function.arguments or "" for tc in tool_calls)
+    assert json.loads(args_str) == {"city": "NYC"}
+
+
+@pytest.mark.parametrize("stream_interval", [1, 2, 4])
+def test_hermes_streaming_multiple_tool_calls_with_stream_interval(
+    qwen_tokenizer: TokenizerLike,
+    any_chat_request: ChatCompletionRequest,
+    stream_interval: int,
+) -> None:
+    """Multiple sequential tool calls must each be streamed correctly."""
+    text = (
+        '<tool_call>{"name": "search", "arguments": {"q": "cats"}}</tool_call>'
+        '<tool_call>{"name": "search", "arguments": {"q": "dogs"}}</tool_call>'
+    )
+    parser = Hermes2ProToolParser(qwen_tokenizer)
+    deltas = _simulate_streaming(
+        qwen_tokenizer, parser, any_chat_request, text, stream_interval
+    )
+
+    # Flatten all DeltaToolCalls across all deltas.
+    all_tool_calls = [tc for d in deltas if d.tool_calls for tc in d.tool_calls]
+
+    # Separate by tool index.
+    tool0 = [tc for tc in all_tool_calls if tc.index == 0]
+    tool1 = [tc for tc in all_tool_calls if tc.index == 1]
+
+    assert tool0[0].function.name == "search"
+    args0 = "".join(tc.function.arguments or "" for tc in tool0)
+    assert json.loads(args0) == {"q": "cats"}
+
+    assert tool1[0].function.name == "search"
+    args1 = "".join(tc.function.arguments or "" for tc in tool1)
+    assert json.loads(args1) == {"q": "dogs"}
+
+
+@pytest.mark.parametrize("stream_interval", [2, 5])
+def test_hermes_streaming_boolean_args_with_stream_interval(
+    qwen_tokenizer: TokenizerLike,
+    any_chat_request: ChatCompletionRequest,
+    stream_interval: int,
+) -> None:
+    """Regression test for bug #19056 with stream_interval > 1."""
+    text = (
+        "<tool_call>\n"
+        '{"name": "final_answer", "arguments": {"trigger": true}}\n'
+        "</tool_call>"
+    )
+    parser = Hermes2ProToolParser(qwen_tokenizer)
+    deltas = _simulate_streaming(
+        qwen_tokenizer, parser, any_chat_request, text, stream_interval
+    )
+
+    tool_calls = [tc for d in deltas if d.tool_calls for tc in d.tool_calls]
+    assert tool_calls[0].function.name == "final_answer"
+    args_str = "".join(tc.function.arguments or "" for tc in tool_calls)
+    assert json.loads(args_str) == {"trigger": True}
+
+
+@pytest.mark.parametrize("stream_interval", [2, 3, 5])
+def test_hermes_streaming_just_forward_text_with_stream_interval(
+    qwen_tokenizer: TokenizerLike,
+    any_chat_request: ChatCompletionRequest,
+    stream_interval: int,
+) -> None:
+    """Plain text with no tool calls must be fully forwarded."""
+    text = "This is plain text with no tool calling involved."
+    parser = Hermes2ProToolParser(qwen_tokenizer)
+    deltas = _simulate_streaming(
+        qwen_tokenizer, parser, any_chat_request, text, stream_interval
+    )
+
+    for d in deltas:
+        assert not d.tool_calls
+    assert "".join(d.content for d in deltas) == text
+
+
 def test_hermes_parser_non_streaming_no_tool_call(
     hermes_parser: ToolParser,
     any_chat_request: ChatCompletionRequest,
@@ -218,3 +387,28 @@ def test_hermes_parser_non_streaming_tool_call_invalid_json(
 
     assert tool_call is not None
     assert not tool_call.tools_called
+
+
+def test_hermes_streaming_content_and_tool_call_in_single_chunk(
+    qwen_tokenizer: TokenizerLike,
+    any_chat_request: ChatCompletionRequest,
+) -> None:
+    """Content + complete tool call in one chunk must both be emitted."""
+    text = 'Hi!<tool_call>{"name": "f", "arguments": {"x": 1}}</tool_call>'
+    # Use a stream_interval large enough to guarantee a single chunk.
+    parser = Hermes2ProToolParser(qwen_tokenizer)
+    deltas = _simulate_streaming(
+        qwen_tokenizer,
+        parser,
+        any_chat_request,
+        text,
+        stream_interval=9999,
+    )
+
+    content_parts = [d.content for d in deltas if d.content]
+    tool_parts = [tc for d in deltas if d.tool_calls for tc in d.tool_calls]
+
+    assert "".join(content_parts) == "Hi!"
+    assert tool_parts[0].function.name == "f"
+    args_str = "".join(tc.function.arguments or "" for tc in tool_parts)
+    assert json.loads(args_str) == {"x": 1}