Turn @config into a dataclass_transform

[hmellor]

Main changes:

• Converts the config decorator into a dataclass_transform
• Now we only have to decorate new configs with config instead of config and dataclass
• It also sets the default ConfigDict for this transformed dataclass to forbid extra fields (cc @mgoin who added this to some configs in /vllm/config/compilation.py)

Other changes:

• Update tests to use config alone
• mypy pre-commit hook updated because mypy needs to import config to understand it
• Update config validator pre-commit hook to use config alone

---

Issues that doing this revealed:

• One test was still passing decoding_config which was ignored prior to this PR
• The same method was being used to generate the dict passed to SpeculativeConfig(**kwargs) and SpeculatorsConfig(**kwargs). This was not a problem for SpeculativeConfig because the PretrainedConfig would just accept the extra kwargs and ignore them. SpeculativeConfig also used to accept and ignore these fields but by adding extra="forbid", this became a problem. This PR also untangles the generation of kwargs for constructing these two classes for Speculators models.

[gemini-code-assist]

Code Review

This pull request correctly refactors the @config decorator into a dataclass_transform, simplifying config class definitions by removing the need for an explicit @dataclass decorator. The changes are applied consistently across the codebase, and the tests and pre-commit hooks are updated accordingly.

I found one issue in the updated validate_config.py pre-commit hook where the logic to validate decorators is flawed. I've provided a suggestion to fix this. Other than that, the changes look good and improve the developer experience when defining new configuration classes.

[mergify]

Hi @hmellor, the pre-commit checks have failed. Please run:

uv pip install pre-commit
pre-commit install
pre-commit run --all-files

Then, commit the changes and push to your branch.

For future commits, pre-commit will run automatically on changed files before each commit.

Tip

Is mypy or markdownlint failing?

mypy and markdownlint are run differently in CI. If the failure is related to either of these checks, please use the following commands to run them locally:

# For mypy (substitute "3.10" with the failing version if needed)
pre-commit run --hook-stage manual mypy-3.10
# For markdownlint
pre-commit run --hook-stage manual markdownlint

[mergify]

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

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

[mergify]

Hi @hmellor, the pre-commit checks have failed. Please run:

uv pip install pre-commit
pre-commit install
pre-commit run --all-files

Then, commit the changes and push to your branch.

For future commits, pre-commit will run automatically on changed files before each commit.

Tip

Is mypy or markdownlint failing?

mypy and markdownlint are run differently in CI. If the failure is related to either of these checks, please use the following commands to run them locally:

# For mypy (substitute "3.10" with the failing version if needed)
pre-commit run --hook-stage manual mypy-3.10
# For markdownlint
pre-commit run --hook-stage manual markdownlint