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☁️ Nx Cloud last updated this comment at 2025-01-13 01:30:24 UTC

As shown in the failed tests this doesn't work as written. I'm guessing that what's happening is that you're deferring the addition of the variables to after the scopes are closed - causing dangingling, unresolved references.

When a scope is finalised we close off the references within the scope. This means we attempt to resolve any unresolved references created in the current or child scopes to variables defined in the current scope. If we don't find the right variable the reference is left as unresolved and we continue to the parent scope.

So if you don't declare the implicit globals early enough then they can't be resolved and so the references are left dangling - which then causes the no-undef rule to error on them.

There's a reason this is a draft. One thing I know I'm doing wrong here is that if there two lib records define the nature of an implicit variable differently (type-only vs. value-only vs. value-and-type), one of them wins at effectively random.

As written this theoretically should run before the global scope is closed, but I'll need to dig into it a bit more. I just wanted to put this out there to get some eyes on the concept.

Ah, I just realized that part of the change is missing here. The invocation of populateGlobalsFromLib was supposed to have been moved to between this.visitChildren() and this.close() in Program.

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This is really cool, thanks for sending @dmichon-msft! I'd love to dive in soon and see if we can get this shipped. But - we're a little swamped catching up on issues after the holiday & new year break, and this is a lot of very nuanced code in a not-very-often changed area of the project. So it'll probably be a little while till we can take a deep look.

In the meantime, what would help us review more quickly:

• I see there are some "Added ... was not covered by tests" annotations: could you either test those, or leave comments explaining that they are tested but the annotations are inaccurate (e.g. from Repo: Merge codecov report from ast-spec into typescript-estree's report #6701 or similar)?
• The populateGlobalsFromLib function has gotten huge and IMO much less readable. maybe split out some well-named helper functions to encapsulate more of the used-only-in-one-place logic/variables?
  • Example: entriesForLib could be a const if the retrieval logic were moved to a separate function
  • Example: implicitVariablesFromLibs's creation & cache checking could be moved to a separate function
• You mentioned local testing: could you post your reproduction(s) and how you got the measurements?

Btw, you don't need to keep merging the latest main in: https://typescript-eslint.io/contributing/pull-requests#updating-over-time. We don't want to give that burden to contributors. Especially if us taking a while to get to a PR makes it worse!

I'm slicing out the easy perf win (caching of Object.entries calls) into its own PR that will be much simpler to review, then I'll refactor this a bit and add more testing to the pieces that power it.

I'm slicing out the easy perf win (caching of Object.entries calls) into its own PR that will be much simpler to review, then I'll refactor this a bit and add more testing to the pieces that power it.

👍 in that case drafting this PR in the meantime. Let me know if it's actually ready for review and I misinterpreted. Exciting stuff! 🙂

👋 Just checking in @dmichon-msft, do you still have time for this very exciting perf work?

The PR with the bigger part of the performance win merged, so this hasn't been high on my priority list. This wouldn't be terribly difficult to get going again, I'd just largely forgotten about it. The new structure should make this pretty simple.