[Bugfix] Enforce installed FlashInfer version to match optional requirement

[mgoin]

Purpose

Previously there was no enforcement on the installed version of FlashInfer, just that the imported function exists. This enforcement should help guide users to install FI using the official pathway and reduce user error when FI function behavior changes.

Test Plan

Test Result

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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 effectively addresses the need to enforce a specific version of FlashInfer. By centralizing the version number in vllm/version.py and using it in setup.py, you've improved maintainability. The addition of a runtime version check in vllm/utils/flashinfer.py is a great step towards preventing user errors and ensuring compatibility. I have one suggestion to make the version validation even more robust.

[gemini-code-assist]

The try...except block does not handle a potential ValueError (or packaging.version.InvalidVersion) that can be raised by packaging.version.parse() if flashinfer.__version__ is not a valid PEP 440 version string. An unhandled exception here would crash the application during initialization. It's safer to catch this exception to prevent such crashes.

Suggested change

	except (ImportError, AttributeError):
	return False
	except (ImportError, AttributeError, ValueError):
	return False

[simon-mo]

Why not >=?

[pavanimajety]

Agree >= would work

[pavanimajety]

Thanks, I agree enforcing FI version is good considering we test a given commit / release of vLLM against a specific FI version.

[mergify]

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

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

[mgoin]

Not needed with #26443