[BugFix] Do not raise a ValueError when tool_choice is set to the supported none option and tools are not defined.

[gcalmettes]

This PR fixes the raise of a ValueError when tool_choice is set to the supported none value.

Currently, the ChatCompletionRequest object supports the none and auto options for the tool_choice field.

However, setting tool_choice to none will raise an error as the current validation check is expecting the tools field to be also set when tool_choice is defined, whatever its value.

{"object":"error","message":"[{'type': 'value_error', 'loc': ('body',), 'msg': 'Value error, When using `tool_choice`, `tools` must be set.', 'input': {'model': 'pixtral', 'messages': [{'role': 'system', 'content': 'You are a helpful assistant'}, {'role': 'user', 'content': 'tell me a short story'}], 'max_tokens': 100, 'temperature': 0.7, 'top_p': 0.7, 'presence_penalty': 0, 'stop': [], 'stream': False, 'tool_choice': 'none'}, 'ctx': {'error': ValueError('When using `tool_choice`, `tools` must be set.')}}]","type":"BadRequestError","param":null,"code":400}%

This PR prevents the ValueError to occur and also ensure that when tool_choice is set to the supported none value, no tools definitions are actually sent to the model.

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[github-actions]

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[DarkLight1337]

cc @K-Mistele can you take a look at this and check whether the docs are up-to-date as well?

[gcalmettes]

Note that we encountered the issue when using vllm with Microsoft semantic-kernel, which forces the tool_choice to none if no tool_choice is set in the request (see here).

[K-Mistele]

Taking a look; this seems pretty straightforward

[mergify]

This pull request has merge conflicts that must be resolved before it can be
merged. Please rebase the PR, @gcalmettes.

https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/working-with-forks/syncing-a-fork

[DarkLight1337]

Thanks for your patience!

[gcalmettes]

@DarkLight1337 it looks like one of the required CI pipeline (for auto-merge) has failed due to timeout to fetch one of the model. Anything I can do on my end for this ? Or does this required force merge ?

[DarkLight1337]

Thanks for the reminder, I have retried the tests just now.