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Convert @babel/parser to TypeScript #14783

merged 9 commits into from Jul 23, 2022


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@JLHwung JLHwung commented Jul 22, 2022

Q                       A
Fixed Issues? Closes #13370
Patch: Bug Fix?
Major: Breaking Change?
Minor: New Feature?
Tests Added + Pass? Yes
Documentation PR Link
Any Dependency Changes?
License MIT

In this PR we converts babel-parser to TypeScript, which marks an end of the transition from Flow (but not the end of improving the codebase typings). I tried to make this PR as small as possible. For those typing errors which can't be fixed at my first glance, I suppress them with @ts-expect-error. Hopefully we will remove most of them when we further improve the parser typings.

Significant changes:

  • An Undone type marker is introduced for those intermediate AST nodes created by startNode
type Undone<T extends NodeType> = Omit<T, "type">;

Accessing the type property is a typing error so we are sure that we didn't do any type differentiation on unfinished AST nodes, otherwise the other properties are typed as the AST definitions in "babel-parser".

  • For parser plugins, if we are calling this.someParserMethod which is not overridden in the plugin, we use super.someParserMethod instead.

Further Improvements that be landed in separate PRs:

  • Cleanup the legacy Flow infrastructure
  • Migrate @babel/parser AST types to @babel/types AST types
  • Cleanup unnecessary @ts-expect-error comments

This PR revives #13370. I should also thank @zxbodya, who maintains the flowts which helps the transition process.

@JLHwung JLHwung added Flow -> TS Tracking repository migration from Flow to TS PR: Internal 🏠 A type of pull request used for our changelog categories labels Jul 22, 2022
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babel-bot commented Jul 22, 2022

Build successful! You can test your changes in the REPL here:

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liuxingbaoyu commented Jul 22, 2022

Amazing PR and at the same time CI is completely green, I like it very much!

@liuxingbaoyu liuxingbaoyu self-requested a review Jul 22, 2022
?{ code?: ParseErrorCode, reasonCode?: string } | boolean,
function toParseErrorCredentials(
b: string,
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@liuxingbaoyu liuxingbaoyu Jul 22, 2022

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export was added before the comment, which seems to be a problem with the automatic conversion.

update: I tried to pick the code block and it failed, see the code before and after here.

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@nicolo-ribaudo nicolo-ribaudo left a comment

Thanks, awesome! I pushed a commit undoing some minor format changes.

@JLHwung JLHwung merged commit a483aa2 into babel:main Jul 23, 2022
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@JLHwung JLHwung deleted the ts-babel-parser branch Jul 23, 2022
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4 participants