Remove default values from InitVars so that they're not stored

[hmellor]

The default values have been moved to a factory lambda that's used by VllmConfig so that VllmConfig can still be default constructed without error.

Replaces the hotfix in #29771

[gemini-code-assist]

Code Review

This pull request refactors SchedulerConfig by removing default values from InitVar fields, moving them to a factory lambda used by VllmConfig. This change is intended to prevent the default values from being stored while allowing VllmConfig to be default-constructed. The changes are logical and well-contained. I have one suggestion to improve the code style by replacing the lambda assignment with a standard function definition, following PEP 8 guidelines for better readability and maintainability.

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

ℹ️ About Codex in GitHub

Codex has been enabled to automatically review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

When you sign up for Codex through ChatGPT, Codex can also answer questions or update the PR, like "@codex address that feedback".

[DarkLight1337]

Does moving the defaults into __post_init__ not work?

[hmellor]

Does moving the defaults into __post_init__ not work?

If we remove the default values from the InitVar definition, they become positional arguments. I've moved the logic so that the default construction values still belong to the SchedulerConfig

[DarkLight1337]

LGTM then, thanks

[hmellor]

Here's a little script you can run to validate the expected behaviour:

from pydantic import ValidationError
from vllm.config import SchedulerConfig

try:
    scheduler_config = SchedulerConfig()
except ValidationError as e:
    # Positional InitVars were missing
    print(f"ValidationError: {e}")

try:
    scheduler_config = SchedulerConfig.default_factory()
    scheduler_config.max_model_len
except AttributeError as e:
    # InitVar does not become an attribute
    print(f"AttributeError: {e}")

Both prints should execute if the SchedulerConfig behaves as expected.

[hmellor]

I turned that little script into a test