[Rocketknight1]

get_json_schema() was supposed to raise on type hints it couldn't parse, like custom classes, but _get_json_schema_type() fell back to {"type": "object"} for anything it didn't recognize, so the error was unreachable. This meant hints like Enum classes, dataclasses or datetime all silently told the model to pass a dict.

This PR adds support for Enum classes, which become an enum of their member values, and makes other unknown classes raise as originally intended. This is a behaviour change, since tools with custom class hints (including return hints) used to get through, but I think a loud failure is better than a schema that's quietly wrong!

Fixes #50556

[Rocketknight1]

cc @qgallouedec, can you do a quick review/approval if you're happy?

[HuggingFaceDocBuilderDev]

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Pages changed in this PR:

• en/chat_extras

[qgallouedec]

Thanks, lgtm.

One question on return hints (edge case, not super important I think): def f(x: int) -> Result works on 5.22 and now raises in apply_chat_template, though its arguments are fine (the model never generates the return value), so leaving return out of the schema when its hint can't be converted would keep these tools working without a wrong schema.

[qgallouedec]

Suggested change

	The model generates the member's value, so a tool with a `color: Color` parameter receives `"red"` rather than `Color.RED`. Call `Color(color)` to get the member back.

[qgallouedec]

@mangeshraut712 automated contributions aren't welcome in Hugging Face repos: each of these reviews costs a maintainer time to read and answer. So please stop commenting all hf PRs.

See the AI usage policy in our contributing guide:

• https://github.com/huggingface/trl/blob/main/CONTRIBUTING.md#coding-with-ai-agents
• https://github.com/huggingface/transformers/blob/main/CONTRIBUTING.md#contribution-rules

More context: https://huggingface.co/blog/qgallouedec/open-source-good-intentions

[Rocketknight1]

@qgallouedec yeah, good point! Dropping return hints rather than throwing an error when we can't parse them, which makes sense since most templates ignore the return hints