[Test]: Hermes tool parser stream output error in Qwen3 case (vllm-project#25203)

Signed-off-by: Andreas Hartel <andreas.hartel@aleph-alpha.com>

Author: ahartel

tests/entrypoints/openai/tool_parsers/test_hermes_tool_parser.py

@@ -5,6 +5,11 @@
 
 import pytest
 
+from vllm.entrypoints.openai.protocol import ChatCompletionRequest
+from vllm.entrypoints.openai.tool_parsers.hermes_tool_parser import (
+    Hermes2ProToolParser)
+from vllm.transformers_utils.tokenizer import AnyTokenizer
+
 from ....utils import RemoteOpenAIServer
 
 MODEL_NAME = "meta-llama/Llama-3.2-1B-Instruct"
@@ -37,7 +42,7 @@
                 },
                 "unit": {
                     "type": "string",
-                    "enum": ["celsius", "fahrenheit"]
+                    "enum": ["celsius", "fahrenheit"],
                 },
             },
             "required": ["location"],
@@ -75,7 +80,7 @@
     "user",
     "content":
     "Hi! Do you have any detailed information about the product id "
-    "7355608 and inserted true?"
+    "7355608 and inserted true?",
 }]
 
 
@@ -144,8 +149,8 @@ async def test_streaming_tool_call():
                 if tool_chunk.function.name:
                     tool_call_chunks[index]["name"] += tool_chunk.function.name
                 if tool_chunk.function.arguments:
-                    tool_call_chunks[index][
-                        "arguments"] += tool_chunk.function.arguments
+                    tool_call_chunks[index]["arguments"] += (
+                        tool_chunk.function.arguments)
 
         assert len(tool_call_chunks) == 1
         reconstructed_tool_call = tool_call_chunks[0]
@@ -234,8 +239,8 @@ async def test_streaming_product_tool_call():
                 if tool_chunk.function.name:
                     tool_call_chunks[index]["name"] += tool_chunk.function.name
                 if tool_chunk.function.arguments:
-                    tool_call_chunks[index][
-                        "arguments"] += tool_chunk.function.arguments
+                    tool_call_chunks[index]["arguments"] += (
+                        tool_chunk.function.arguments)
 
         assert len(tool_call_chunks) == 1
         reconstructed_tool_call = tool_call_chunks[0]
@@ -258,3 +263,195 @@ async def test_streaming_product_tool_call():
         print("\n[Streaming Product Test Passed]")
         print(f"Reconstructed Tool Call: {reconstructed_tool_call['name']}")
         print(f"Reconstructed Arguments: {arguments}")
+
+
+@pytest.fixture
+def qwen_tokenizer() -> AnyTokenizer:
+    from vllm.transformers_utils.tokenizer import get_tokenizer
+
+    return get_tokenizer("Qwen/Qwen3-32B")
+
+
+@pytest.fixture
+def hermes_parser(qwen_tokenizer: AnyTokenizer) -> Hermes2ProToolParser:
+    return Hermes2ProToolParser(qwen_tokenizer)
+
+
+@pytest.fixture
+def any_chat_request() -> ChatCompletionRequest:
+    return ChatCompletionRequest(
+        seed=42,
+        model="Qwen/Qwen3-32B",
+        messages=[],
+    )
+
+
+def test_hermes_parser_streaming_just_forward_text(
+    qwen_tokenizer: AnyTokenizer,
+    hermes_parser: Hermes2ProToolParser,
+    any_chat_request: ChatCompletionRequest,
+) -> None:
+    text = (
+        """This is some prior text that has nothing to do with tool calling."""
+    )
+    tokens = qwen_tokenizer.encode(text)
+    previous_text = ""
+    delta_messages = []
+    for token in tokens:
+        delta_text = qwen_tokenizer.decode([token])
+        current_text = previous_text + delta_text
+        delta = hermes_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=[],
+            request=any_chat_request,
+        )
+        previous_text = current_text
+        delta_messages.append(delta)
+
+    for delta in delta_messages:
+        assert delta is not None
+        assert not delta.tool_calls
+
+    print(delta_messages)
+    assert "".join([delta.content for delta in delta_messages]) == text
+
+
+def test_hermes_parser_streaming_failure_case_bug_19056(
+    qwen_tokenizer: AnyTokenizer,
+    hermes_parser: Hermes2ProToolParser,
+    any_chat_request: ChatCompletionRequest,
+) -> None:
+    text = """<tool_call>
+{"name": "final_answer", "arguments": {"trigger": true}}
+</tool_call>"""
+    tokens = qwen_tokenizer.encode(text)
+    previous_text = ""
+    delta_messages = []
+    for token in tokens:
+        text = qwen_tokenizer.decode([token])
+        current_text = previous_text + text
+        delta = hermes_parser.extract_tool_calls_streaming(
+            previous_text=previous_text,
+            current_text=current_text,
+            delta_text=text,
+            previous_token_ids=[],
+            current_token_ids=[],
+            delta_token_ids=[],
+            request=any_chat_request,
+        )
+        previous_text = current_text
+        if delta is not None:
+            delta_messages.append(delta)
+
+    assert delta_messages[0].tool_calls[0].function.name == "final_answer"
+    tool_call_args = "".join(delta.tool_calls[0].function.arguments or ""
+                             for delta in delta_messages)
+    assert tool_call_args == '{"trigger": true}'
+
+
+def test_hermes_parser_streaming(
+    qwen_tokenizer: AnyTokenizer,
+    hermes_parser: Hermes2ProToolParser,
+    any_chat_request: ChatCompletionRequest,
+) -> None:
+    text = '<tool_call>\
+{"name": "get_current_temperature",\
+"arguments": {"location":\
+"San Francisco, California, United States", "unit": "celsius"}}\
+</tool_call>'
+
+    tokens = qwen_tokenizer.encode(text)
+    previous_text = ""
+    delta_messages = []
+    for token in tokens:
+        text = qwen_tokenizer.decode([token])
+        current_text = previous_text + text
+        delta = hermes_parser.extract_tool_calls_streaming(
+            previous_text=previous_text,
+            current_text=current_text,
+            delta_text=text,
+            previous_token_ids=[],
+            current_token_ids=[],
+            delta_token_ids=[],
+            request=any_chat_request,
+        )
+        previous_text = current_text
+        if delta is not None:
+            delta_messages.append(delta)
+    print(delta_messages)
+    assert (delta_messages[0].tool_calls[0].function.name ==
+            "get_current_temperature")
+    tool_call_args = "".join(delta.tool_calls[0].function.arguments or ""
+                             for delta in delta_messages)
+    assert tool_call_args == (
+        '{"location":"San Francisco, California, United States", '
+        '"unit": "celsius"}')
+
+
+def test_hermes_parser_non_streaming_no_tool_call(
+    hermes_parser: Hermes2ProToolParser,
+    any_chat_request: ChatCompletionRequest,
+) -> None:
+    text = """This is not a tool call."""
+    tool_call = hermes_parser.extract_tool_calls(
+        model_output=text,
+        request=any_chat_request,
+    )
+
+    assert tool_call is not None
+    assert not tool_call.tools_called
+
+
+def test_hermes_parser_non_streaming_tool_call_between_tags(
+    hermes_parser: Hermes2ProToolParser,
+    any_chat_request: ChatCompletionRequest,
+) -> None:
+    text = """<tool_call>
+{"name": "final_answer", "arguments": {"trigger": true}}
+</tool_call>"""
+    tool_call = hermes_parser.extract_tool_calls(
+        model_output=text,
+        request=any_chat_request,
+    )
+
+    assert tool_call is not None
+    assert tool_call.tools_called
+    assert tool_call.tool_calls[0].function.name == "final_answer"
+    assert tool_call.tool_calls[0].function.arguments == '{"trigger": true}'
+
+
+def test_hermes_parser_non_streaming_tool_call_until_eos(
+    hermes_parser: Hermes2ProToolParser,
+    any_chat_request: ChatCompletionRequest,
+) -> None:
+    text = """<tool_call>
+{"name": "final_answer", "arguments": {"trigger": true}}"""
+    tool_call = hermes_parser.extract_tool_calls(
+        model_output=text,
+        request=any_chat_request,
+    )
+
+    assert tool_call is not None
+    assert tool_call.tools_called
+    assert tool_call.tool_calls[0].function.name == "final_answer"
+    assert tool_call.tool_calls[0].function.arguments == '{"trigger": true}'
+
+
+def test_hermes_parser_non_streaming_tool_call_invalid_json(
+    hermes_parser: Hermes2ProToolParser,
+    any_chat_request: ChatCompletionRequest,
+) -> None:
+    # Missing closing brace to trigger exception
+    text = """<tool_call>
+{"name": "final_answer", "arguments": {"trigger": true}"""
+    tool_call = hermes_parser.extract_tool_calls(
+        model_output=text,
+        request=any_chat_request,
+    )
+
+    assert tool_call is not None
+    assert not tool_call.tools_called