Enable mypy type checking

[simon-mo]

Anything you want to discuss about vllm.

Even though vLLM is type annotated but we did not enable type checking. It would be useful to add it, even incrementally.

[rkooo567]

The current remaining

[rkooo567] mypy vllm/engine/*.py --follow-imports=skip --config-file pyproject.toml
[rkooo567] mypy vllm/worker/*.py --follow-imports=skip --config-file pyproject.toml
[rkooo567] mypy vllm/spec_decode/*.py --follow-imports=skip --config-file pyproject.toml
[rkooo567] mypy vllm/model_executor/*.py --follow-imports=skip --config-file pyproject.toml
mypy vllm/lora/*.py --follow-imports=skip --config-file pyproject.toml
mypy vlllm/entrypoints/openai/*.py --follow-imports=skip --config=file pyprojet.toml
mypy vllm/transformers_utils/configs/*.py --follow-imports=skip --config=file pyprojet.toml
mypy vllm/transformers_utils/tokenizers/*.py --follow-imports=skip --config=file pyprojet.toml
mypy vllm/distributed/device_communicators/*.py --follow-imports=skip --config=file pyprojet.toml
mypy vllm/attention/backends/*.py --follow-imports=skip --config=file pyprojet.toml
mypy vllm/transformers_utils/tokenizer_group/*.py --follow-imports=skip --config=file pyprojet.toml
mypy vllm/core/block/*.py --follow-imports=skip --config=file pyprojet.toml
mypy vllm/model_executor/layers/*.py --follow-imports=skip --config=file pyprojet.toml
mypy vllm/model_executor/layers/*.py --follow-imports=skip --config=file pyprojet.toml

and misc after

[DarkLight1337]

For those who are new to the vLLM repo, determining the correct type of each variable is a great way to enhance your understanding of how the code is connected together.

[DarkLight1337]

Quick update on the latest progress:

• @rkooo567 has enabled type checking for main vllm library ([mypy][7/N] Cover all directories #4555 being the last PR)
• I have enabled type checking for tests directory ([mypy] Enable type checking for test directory #5017)

However, the effectiveness of type checking is still quite minimal because imported types are currently treated as Any due to the setting --follow_imports=skip:

vllm/pyproject.toml

Lines 46 to 51 in 2be6955

	[tool.mypy]
	python_version = "3.8"
	ignore_missing_imports = true
	check_untyped_defs = true
	follow_imports = "skip"

My IDE, which uses Pyright basic mode, still flags a lot of errors, showing that there is much work to be done.

Moving forward, we should work on gradually applying --follow_imports=normal for each directory, fixing errors as we go. I recommend going through the directories following a similar order as @rkooo567 did (these search filters should be able to locate the relevant PRs).

[youkaichao]

Cool, looking forward to the progress.

[rkooo567]

This is a great issue to improve the code quality of the repo, so please feel free to work on it if anyone is interested! One example PR in the past #4043

[jberkhahn]

I'm taking a crack at vllm/core, just to get my feet wet with the codebase.