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feat(typescript-estree): add experimental mode for type-aware linting that uses a language service instead of a builder #6172

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@bradzacher bradzacher commented Dec 6, 2022

Overview

This is just an experiment to help address memory issues (#1192), maybe performance, and maybe out-of-sync types (#5845).

I was looking into some code around the place and noticed that TS exposes the concept of a "document registry" - which is a shared cache that can be reused across certain TS data structures to deduplicate memory usage (and I assume improve performance by deduplicating work).

This PR implements a new parser strategy which uses TS's "Language Service" tooling, which in turn leverages the document registry. "persistent parse" tests pass - which at least proves that it works in some manner of speaking.

One interesting thing to note here is under the hood the language serivce doesn't use a builder program. I believe the idea is that the document registry is supposed to forego the performance implications of that? I don't know exactly - it will require more testing. Though it's worth mentioning that this means this could replace our current "single-run" codepaths because it doesn't use a builder program.

TODO:

  • figure out how to roll-back "dirty" states
  • memory pressure testing
  • runtime performance testing

… that uses a language service instead of a builder program

## PR Checklist

- [x] Steps in [CONTRIBUTING.md](https://github.com/typescript-eslint/typescript-eslint/blob/main/CONTRIBUTING.md) were taken

## Overview

This is just an experiment to help address memory issues (#1192), maybe performance, and maybe out-of-sync types (#5845).

I was looking into some code around the place and noticed that TS exposes the concept of a "document registry" - which is a shared cache that can be reused across certain TS data structures to deduplicate memory usage (and I assume improve performance by deduplicating work).

This PR implements a new parser strategy which uses TS's "Language Service" tooling, which in turn leverages the document registry. "persistent parse" tests pass - which at least proves that it works in some manner of speaking.

One interesting thing to note here is under the hood the language serivce doesn't use a builder program. I believe the idea is that the document registry is supposed to forego the performance implications of that? I don't know exactly - it will require more testing. Though it's worth mentioning that this means this could replace our current "single-run" codepaths because it doesn't use a builder program.

TODO:
- figure out how to roll-back "dirty" states
- memory pressure testing
- runtime performance testing
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Thanks for the PR, @bradzacher!

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@bradzacher
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something weird is happening on the CI - dunno why it's OOMing.
cannot reproduce locally so that's fun.

@bradzacher
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Cc @jakebailey I know you had an inclination about helping us improve the perf of the tooling.

I was hoping you could help me by providing some TS insider insight ☺

Do you think this approach will help out a lot compared to the existing builder program approach?
From what I can tell by poking around and reading it'll at least save us a bunch of memory - though not too sure about runtime cost/savings yet.

Would it be worth us building our own layer on top of the document registry instead of reusing the language service?

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Honestly, I have no clue; @sheetalkamat or someone may have better insight.

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Closing this old draft for housekeeping since there are merge conflicts and it's taking up space in the open PRs list. Nothing bad will happen in my housekeeping if this is re-opened. Don't mind me. 😄

@github-actions github-actions bot locked as resolved and limited conversation to collaborators Feb 27, 2023
@bradzacher bradzacher reopened this Feb 27, 2023
@bradzacher bradzacher added the DO NOT MERGE PRs which should not be merged yet label Feb 27, 2023
@bradzacher bradzacher added the enhancement New feature or request label Apr 17, 2023
@JoshuaKGoldberg
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@bradzacher do you still want to work on this now that EXPERIMENTAL_useProjectService is in (#6754)?

@bradzacher
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Let's put a pin in this - if we find that the project service works for all cases then there's no need for us to worry about improving the manual config case, I think.
We may want to re-investigate this if there are strong usecases that it doesn't support - but I'm optimistic we won't have to.

@bradzacher bradzacher closed this Jul 17, 2023
@bradzacher bradzacher deleted the pr6172 branch July 17, 2023 02:02
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3 participants