[Test]: Hermes tool parser stream output error in Qwen3 case

[ahartel]

Purpose

Fix: #19056

Test Plan

Added some tests in the PR.

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[gemini-code-assist]

Code Review

This pull request addresses a streaming output error in the Hermes tool parser, particularly for the Qwen3 model, by correcting the logic for handling partially streamed JSON arguments. The addition of a comprehensive test suite for the Hermes parser, including specific cases for Qwen tokenization, streaming, and non-streaming scenarios, is a great improvement and significantly enhances the robustness of the parser. While the main fix is sound, I've identified a pre-existing critical bug in the type checking logic that should be addressed.

[ahartel]

@cedonley I saw that you changed lines 369-373 of hermes_tool_parser.py in #10979. The actual fix I am proposing here touches those lines as well by removing 2 string slice operations. Can you remember why you introduced them? Or do you have test cases at hand that I could add to the code base to make sure that they still run?

[ahartel]

Just found this question as well on this topic. The question and your answer seem to suggest that my fix might be applicable.

[tugot17]

The tests seem to pass and all looks fine;

Do you have any idea why it used to be

if (delta_text not in cur_arguments_json[:-2]):

before?

[ahartel]

The tests seem to pass and all looks fine;

Do you have any idea why it used to be

if (delta_text not in cur_arguments_json[:-2]):

before?

No, unfortunately not. Let's see if @cedonley has any insights. See also the links to a previous discussion in my previous comment.

[chaunceyjiang]

Hi @ahartel Could you retest based on the main branch to see if the issue still exists?

[ahartel]

Hi @ahartel Could you retest based on the main branch to see if the issue still exists?

My newly added tests do indeed pass on main and used to fail previously. Seems to have been fixed. Thanks for pointing that out.

@chaunceyjiang Would you mind merging the changes to file tests/entrypoints/openai/tool_parsers/test_hermes_tool_parser.py? This would add some more test coverage and maybe also document the bevavior of the hermes tool parser.

[chaunceyjiang]

@chaunceyjiang Would you mind merging the changes to file tests/entrypoints/openai/tool_parsers/test_hermes_tool_parser.py? This would add some more test coverage and maybe also document the bevavior of the hermes tool parser.

Of course, this is a new test case. We can move forward quickly.

[ahartel]

Thanks. I updated my PR to only contain my test additions (plus some very minor reformattings)

[chaunceyjiang]

Thanks~

[ahartel]

Thank you for your support @chaunceyjiang