[BugFix]: Fix local mypy issues

[hickeyma]

Purpose

When you run pre-commit in local dev environment, you get the following mypy errors:

$ pre-commit run --all-files    

ruff check..........................................................................................Passed
ruff format.........................................................................................Passed
typos...............................................................................................Passed
clang-format........................................................................................Passed
Lint GitHub Actions workflow files..................................................................Passed
pip-compile.........................................................................................Passed
reformat nightly_torch_test.txt to be in sync with test.in..........................................Passed

Run mypy locally for lowest supported Python version................................................Failed
- hook id: mypy-local
- exit code: 1

$ mypy --python-version 3.10 --follow-imports skip 
vllm/entrypoints/openai/chat_completion/protocol.py:466: error: Value of type variable "_DataclassT" of "replace" cannot be "StructuredOutputsParams"  [type-var]
vllm/entrypoints/openai/responses/protocol.py:339: error: Unexpected keyword argument "json" for "StructuredOutputsParams"  [call-arg]
vllm/entrypoints/openai/completion/protocol.py:272: error: Value of type variable "_DataclassT" of "replace" cannot be "StructuredOutputsParams"  [type-var]
vllm/distributed/kv_transfer/kv_connector/v1/nixl_connector.py:938: error: Module has no attribute "sched_setaffinity"  [attr-defined]
vllm/entrypoints/openai/responses/serving.py:503: error: Value of type variable "_DataclassT" of "replace" cannot be "StructuredOutputsParams"  [type-var]
Found 5 errors in 5 files (checked 645 source files)

[...]

This PR fixes the issues as shown below.

MyPy issues handled as follows:

• Pydantic dataclasses does not satisfy mypy's type system with replace(), even though they are fully compatible at runtime. Therefore, ignore
• Skipped import issue that StructuredOutputsParams has with json prioperty in vllm/entrypoints/openai/responses/protocol.py. Therefore, ignore as enabling the imports raises lot of other issues which are unrelated.
• sched_setaffinity() is a Linux only OS command and therefore added a check in llm/distributed/kv_transfer/kv_connector/v1/nixl_connector.py for it.

Additionally:

• Renamed json import because property called json in class also in vllm/sampling_params.py. This is for hygiene reasons.

---

Essential Elements of an Effective PR Description Checklist

• The purpose of the PR, such as "Fix some issue (link existing issues this PR will resolve)".
• The test plan, such as providing test command.
• The test results, such as pasting the results comparison before and after, or e2e results
• (Optional) The necessary documentation update, such as updating supported_models.md and examples for a new model.
• (Optional) Release notes update. If your change is user facing, please update the release notes draft in the Google Doc.

[gemini-code-assist]

Code Review

This pull request addresses several mypy issues found during local development. The changes primarily involve adding type: ignore comments to suppress type errors related to Pydantic dataclasses and dataclasses.replace, which is a reasonable approach for these known mypy limitations. A platform-specific check for os.sched_setaffinity has been correctly added to prevent errors on non-Linux systems. However, there's a potential issue in vllm/sampling_params.py where import json_mod is used. This seems to assume a new file that isn't part of the PR. I've suggested using a standard alias import json as json_mod to resolve the name clash cleanly.

[njhill]

Thanks @hickeyma, I haven't looked closely but I think this may be a dup of #34693?

[hickeyma]

Thanks @hickeyma, I haven't looked closely but I think this may be a dup of #34693?

Thanks @njhill for making me aware of it, I didn't see it when I checked before I started my PR. Yes, there is duplicate for StructuredOutputsParams replace() issue but not for the other fixes. Also, I took a different approach to StructuredOutputsParams replace() issue as commented in #34693 (review).

[hmellor]

As mentioned in the other PR, you could try

vllm/vllm/config/utils.py

Lines 105 to 113 in 1391378

	def replace(dataclass_instance: ConfigT, /, **kwargs) -> ConfigT:
	"""Like [`dataclasses.replace`](https://docs.python.org/3/library/dataclasses.html#dataclasses.replace),
	but compatible with Pydantic dataclasses which use `pydantic.fields.Field` instead
	of `dataclasses.field`"""
	cls = type(dataclass_instance)
	dataclass_dict = dataclass_instance.__dict__
	dataclass_dict = {k: v for k, v in dataclass_dict.items() if is_init_field(cls, k)}
	dataclass_dict.update(kwargs)
	return cls(**dataclass_dict)

which is pydntic compatible

[hickeyma]

Thanks @hmellor for pointing out an existing implementation of replace(). What is the value of adding the override method? If its just for mypy type error, if so is it worth the overhead and potential maintenance?

[hickeyma]

Ok, I think I see. You lose the validation otherwise.

[hickeyma]

@hmellor I have updated to use the pydantic compatible replace() function.

[hmellor]

The main reason that dataclasses.replace isn't compatible with pydantic dataclasses is that it doesn't look inside pydantic.fields.Field to check for init. So then it will try to initialise the dataclass with fields that are post-init-only. This reimplementation respects the init by checking is_init_field.

And yes it allows us to continue using pydantic and all the validation that comes with it

[mergify]

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

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

[hmellor]

LGTM, thanks for helping reduce the mypy based weirdness in vLLM!

[hickeyma]

LGTM, thanks for helping reduce the mypy based weirdness in vLLM!

Thanks @hmellor for the reviews and feedback.