Promise.allSettled type problem

[dogukanakkaya]

This code gives me some null errors even though i filtered the array. Type 'number | null' is not assignable to type 'number'.

promiseResults.map(promiseResult => promiseResult.status === 'fulfilled' ? promiseResult.value : null).filter(Boolean)

And also below code gives me Property 'value' does not exist on type 'PromiseRejectedResult'. even though i filtered for fulfilled promise results.

promiseResults.filter(promiseResult => promiseResult.status === 'fulfilled').map(promiseResult => promiseResult.value)

[fatcerberus]

Neither Boolean nor txData => txData.status === 'fulfilled' are type guards. You need to pass a type guard (a function with an explicit param is T return type annotation) for filter to narrow the type of the array.

[SPGoding]

See also #16655 for .filter(Boolean).

[dogukanakkaya]

I already have some workaround for those, but i am still not convinced that this is not an issue (especially for filter if not for Promise Result types)? Shouldn't Typescript compiler already infers the types for filtering with var !== null.

Some of those workarounds for filter are below code and i can make it work also with as PromiseFulfilledResult for Promise thing.

const numbers = [1, 2, 3, 4, null];
numbers.filter((num): num is number => num !== null);

[MartinJohns]

Shouldn't Typescript compiler already infers the types for filtering with var !== null.

See #38390.