[Bugfix] Fail instead of ignoring when CompilationConfig gets invalid args

[mgoin]

Purpose

I noticed this when trying to run with an old flag of -cc.use_inductor=False where I saw that my arg was completely ignored:

vllm serve Qwen/Qwen3-Next-80B-A3B-Instruct-FP8 --port 9000 --tensor-parallel-size 1 --max-model-len 50k --speculative-config '{"method":"qwen3_next_mtp","num_speculative_tokens":2}' -cc.use_inductor=false
(APIServer pid=3033517) INFO 12-15 12:44:29 [api_server.py:1351] vLLM API server version 0.11.2.dev695+g5c213d289
(APIServer pid=3033517) INFO 12-15 12:44:29 [utils.py:253] non-default args: {'model_tag': 'Qwen/Qwen3-Next-80B-A3B-Instruct-FP8', 'port': 9000, 'model': 'Qwen/Qwen3-Next-80B-A3B-Instruct-FP8', 'max_model_len': 50000, 'speculative_config': {'method': 'qwen3_next_mtp', 'num_speculative_tokens': 2}}

Now when I run the same command, I see a usage failure as expected:

vllm serve Qwen/Qwen3-Next-80B-A3B-Instruct-FP8 --port 9000 --tensor-parallel-size 1 --max-model-len 50k --speculative-config '{"method":"qwen3_next_mtp","num_speculative_tokens":2}' -cc.use_inductor=false
usage: vllm serve [model_tag] [options]
vllm serve: error: argument --compilation-config/-cc: 1 validation error for CompilationConfig
use_inductor
  Unexpected keyword argument [type=unexpected_keyword_argument, input_value=False, input_type=bool]
    For further information visit https://errors.pydantic.dev/2.12/v/unexpected_keyword_argument

Test Plan

Test Result

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[gemini-code-assist]

Code Review

This pull request addresses an issue where invalid arguments for CompilationConfig were silently ignored. By adding config=ConfigDict(extra="forbid") to the Pydantic dataclasses PassConfig, DynamicShapesConfig, and CompilationConfig, the code now correctly raises a validation error for unexpected arguments. This improves the robustness of the configuration parsing and provides clear feedback to users about invalid flags. The related test cases in tests/benchmarks/test_param_sweep.py that used a now-invalid argument have been correctly removed. The changes are well-targeted and effectively resolve the issue. The implementation is clean and follows best practices for Pydantic configuration. I have reviewed the changes and found no issues.

[hmellor]

Good catch, this should probably be implemented in all config classes. At some point I'll have another look into merging

@config
@dataclass

into just

@config

where defaults like this can be set.