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project service cleanupProjectsAndScriptInfos openClientFileWithNormalizedPath openClientFile

🙁 Actual behavior

TypeScript project services open a file with service.openClientFile(filePathAbsolute, ...). That internally calls to a cleanupProjectsAndScriptInfos to clean up projects, such as removing orphans. There's no way to skip that cleanup.

When using typescript-eslint's parserOptions.projectService, that cleanup adds (seemingly?) unnecessary overhead per file being linted.

🙂 Expected behavior

When I tried commenting out its contents of cleanupProjectsAndScriptInfos locally, the time for a lint run of ~1024 files with the project service speed up by ~15-20%, from ~3.2 seconds to ~2.5 seconds. ⚡

Request: could we add an option to the ProjectService class to skip cleanups, please?

Alternate request: failing that, maybe the cleanups can be debounced and/or delayed in some way? E.g. added to a queue that only executes if the project service is still active?

Additional information about the issue

On the TypeScript side:

• Point of comparison: JoshuaKGoldberg@2ae3568 would be one way of doing this.
• Handle config file change and default project management #58486 is the PR that introduced cleanupProjectsAndScriptInfos.

On the typescript-eslint side:

• https://github.com/typescript-eslint/performance is the performance repository showing how to create these profiles.
  • https://github.com/typescript-eslint/performance/blob/main/README.md#comparison-project-service-client-file-cleanups has the measurements for this specific investigation.
• feat(typescript-estree): add EXPERIMENTAL_useProjectService option to use TypeScript project service typescript-eslint/typescript-eslint#6754 is the PR that first added usage of the project service in typescript-eslint.
• We in ESLint-land can't explicitly tell TypeScript when files are opened or closed: feat: parsing session objects eslint/rfcs#102. But in typescript-eslint specifically we have an inference of when we're in "single-run" mode: https://v8--typescript-eslint.netlify.app/packages/parser#disallowautomaticsingleruninference.

cc @sheetalkamat as FYI, after a pairing with @jakebailey.

@jakebailey suggested I also include a screenshot like this speedscope.app view of an ESLint CLI run with parserOptions.projectService: