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import { InvariantError } from '../../shared/lib/invariant-error'
/**
* Provides a `waitUntil` implementation which gathers promises to be awaited later (via {@link AwaiterMulti.awaiting}).
* Unlike a simple `Promise.all`, {@link AwaiterMulti} works recursively --
* if a promise passed to {@link AwaiterMulti.waitUntil} calls `waitUntil` again,
* that second promise will also be awaited.
*/
export class AwaiterMulti {
private promises: Set<Promise<unknown>> = new Set()
private onError: (error: unknown) => void
constructor({ onError }: { onError?: (error: unknown) => void } = {}) {
this.onError = onError ?? console.error
}
public waitUntil = (promise: Promise<unknown>): void => {
// if a promise settles before we await it, we should drop it --
// storing them indefinitely could result in a memory leak.
const cleanup = () => {
this.promises.delete(promise)
}
promise.then(cleanup, (err) => {
cleanup()
this.onError(err)
})
this.promises.add(promise)
}
public async awaiting(): Promise<void> {
while (this.promises.size > 0) {
const promises = Array.from(this.promises)
this.promises.clear()
await Promise.allSettled(promises)
}
}
}
/**
* Like {@link AwaiterMulti}, but can only be awaited once.
* If {@link AwaiterOnce.waitUntil} is called after that, it will throw.
*/
export class AwaiterOnce {
private awaiter: AwaiterMulti
private done: boolean = false
private pending: Promise<void> | undefined
constructor(options: { onError?: (error: unknown) => void } = {}) {
this.awaiter = new AwaiterMulti(options)
}
public waitUntil = (promise: Promise<unknown>): void => {
if (this.done) {
throw new InvariantError(
'Cannot call waitUntil() on an AwaiterOnce that was already awaited'
)
}
return this.awaiter.waitUntil(promise)
}
public async awaiting(): Promise<void> {
if (!this.pending) {
this.pending = this.awaiter.awaiting().finally(() => {
this.done = true
})
}
return this.pending
}
}
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