Request for Public API Access to RxJS Schedulers

[kramar]

It would be beneficial if AsapScheduler, AsapAction, AsyncScheduler, and AsyncAction were exposed in the public API. This would help address an inherent problem when using the out-of-the-box RxJS asapScheduler within Angular applications.

Current Behavior

Internally, the AsapScheduler uses setImmediate to schedule actions on the microtask queue. However, it only invokes setImmediate once per microtask tick. Subsequent actions scheduled during the same tick are simply appended to the internal actions array without triggering another setImmediate call. All actions are then flushed together during the same tick.

The Problem in Angular Context

This batching behavior can cause critical issues in Angular applications when actions are scheduled from different zone contexts. Specifically:

1. Zone Context Locking: If actions are scheduled both inside and outside the NgZone during the same microtask tick, the zone context of the first scheduled action determines the zone in which all subsequent actions will execute.

2. Change Detection Outside NgZone: This becomes particularly problematic when a scheduled action triggers change detection. If that change detection runs outside the NgZone:

   • Components created during that change detection will have their host bindings and event listeners attached outside the NgZone
   • Events emitted from these components will no longer trigger application-level change detection
   • This defeats the core purpose of Angular's NgZone mechanism

Proposed Solution

To resolve this issue, we need the ability to create separate scheduler instances for different zone contexts:

const asapOutsideNgScheduler: AsapScheduler = new AsapScheduler(AsapAction);

However, this solution requires access to the AsapScheduler and AsapAction classes, which are currently internal to RxJS.

Request

Please consider exposing AsapScheduler, AsapAction, AsyncScheduler, and AsyncAction as part of the public API to enable Angular developers to properly manage zone contexts when using schedulers.