exhaustAll never completes when lastValueFrom is used

[mlegenhausen]

Describe the bug

exhaustAll does not behave the same as exhaustMap(identity)

Expected behavior

I would expect that exhaustAll should behave the same as exhaustMap(identity)

Reproduction code

import { exhaustAll, exhaustMap, firstValueFrom, lastValueFrom, of, identity } from 'rxjs'

const a = of(of(1))

const a1 = await firstValueFrom(a.pipe(exhaustMap(identity)))
assert.deepStrictEqual(a1, 1) // success

const a2 = await firstValueFrom(a.pipe(exhaustAll()))
assert.deepStrictEqual(a2, 1) // success

const a3 = await lastValueFrom(a.pipe(exhaustMap(identity)))
assert.deepStrictEqual(a3, 1) // success

const a4 = await lastValueFrom(a.pipe(exhaustAll()))
assert.deepStrictEqual(a4, 1) // timeout cause `a4` never resolves

Reproduction URL

No response

Version

7.5.5

Environment

No response

Additional context

No response

[ajafff]

I can confirm that the resulting Observable never completes if the last inner Observable completes synchronously. exhaustMap on the other hand handles this case properly.

I will open a PR to remove the whole implementation of the operator and instead return exhaustMap(identity). All related operators (mergeAll, switchAll, ...) already do the same