microsoft / microsoft/TypeScript
`forEachChild` is hard to use with async API
@andrewbranch is already working on this.
Since Sep 1, 2026.
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Description
If you try to use the async API, it's a challenge today. The API provides a synchronous tree traversal function (`forEachChild`), but pulling on semantic information is asynchronous.
The problem isn't the mixture itself - it's that `forEachChild` stops walking when the visitor function returns a truthy result. This makes it impractical to use with async APIs because every async function returns a `Promise` which is truthy.
The current workarounds are a little awkward, basically introducing a layer of indirection between the traversal function and `forEachChild` that uses intermediate queues.
I'm not sure if there's an ideal solution - there's at least two problems right now:
- it feels like we could benefit from a `forEachChildAsync` or something like that.
- using `forEachChild` is a foot-gun if you've decided to use the async API.
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