fix: qwen3 nonstream parse with no or uncompleted think content

[ywx217]

Motivation

Behaviors of qwen3 reasoning parser are fixed:

• In non stream mode, when thinking is disabled, output is returned as reasoning_content.
• In non stream mode, when thinking content is larger than max_tokens, parser cannot handle output without </think> token. (Mentioned in issue [Bug] Qwen3 Reasoning Parser 解析错误 #3664)

Modification

• qwen_qwq_reasoning_parser.py
  • When stream=False and enable_thinking=False, there's no <think> tag, so the whole model output should be regarded as content, not reasoning_content.
  • When stream=False, enable_thinking=True and max_token is a small value, incomplete think content can be correctly parsed.
• test_qwen3_parser.py
  • relative test cases added

Checklist

1. Pre-commit or other linting tools are used to fix the potential lint issues.
2. The modification is covered by complete unit tests. If not, please add more unit tests to ensure the correctness.
3. If the modification has a dependency on downstream projects of a newer version, this PR should be tested with all supported versions of downstream projects.
4. The documentation has been modified accordingly, like docstring or example tutorials.

[RunningLeon]

what if the model does not have reasoning ability, but the output becomes reasoning_content?

[ywx217]

Any specific model name and model output for this case?

[ywx217]

When the model does not have reasoning ability, the output should be normal content, not reasoning.

[RunningLeon]

hi, when enable_thinking=False, the parser is disabled in main branch

lmdeploy/lmdeploy/serve/openai/api_server.py

Line 508 in 5f0647f

if VariableInterface.reasoning_parser is not None and request.enable_thinking is not False:

[lvhan028]

why perform _trim_newlines?

[ywx217]

<think>\n{reasoning_content}\n</think>

to remove \n before and after reasoning_content

[lvhan028]

May provide reproducing code

[lvhan028]

@RunningLeon Is it fixed when you supported interns1 reasoning parser?

[RunningLeon]

@RunningLeon Is it fixed when you supported interns1 reasoning parser?

The first problem in the below should be fixed.
@ywx217 hi, as for the second one, does a user really need the uncomplete thinking_content in the case? If reasonable, this would be included.

• When stream=False and enable_thinking=False, there's no <think> tag, so the whole model output should be regarded as content, not reasoning_content.
  - When stream=False, enable_thinking=True and max_token is a small value, incomplete think content can be correctly parsed.