refactor: Replace Zone.scheduleMacroTask with ExperimentalPendingTasks

Author: mmalerba

src/zones.ts

@@ -1,5 +1,10 @@
 /* eslint-disable @typescript-eslint/ban-ts-comment */
-import { Injectable, NgZone } from "@angular/core";
+import {
+  ExperimentalPendingTasks,
+  Injectable,
+  NgZone,
+  inject,
+} from "@angular/core";
 import {
   Observable,
   Operator,
@@ -48,17 +53,16 @@ export class ɵZoneScheduler implements SchedulerLike {
 }
 
 class BlockUntilFirstOperator<T> implements Operator<T, T> {
-  // @ts-ignore
-  private task: MacroTask | null = null;
-
-  constructor(private zone: any) {}
+  constructor(
+    private zone: any,
+    private pendingTasks: ExperimentalPendingTasks
+  ) {}
 
   call(subscriber: Subscriber<T>, source: Observable<T>): TeardownLogic {
-    const unscheduleTask = this.unscheduleTask.bind(this);
-    // @ts-ignore
-    this.task = this.zone.run(() =>
-      Zone.current.scheduleMacroTask("firebaseZoneBlock", noop, {}, noop, noop)
-    );
+    const taskDone = this.zone.run(() => this.pendingTasks.add());
+    // maybe this is a race condition, invoke in a timeout
+    // hold for 10ms while I try to figure out what is going on
+    const unscheduleTask = () => setTimeout(taskDone, 10);
 
     return source
       .pipe(
@@ -71,17 +75,6 @@ class BlockUntilFirstOperator<T> implements Operator<T, T> {
       .subscribe(subscriber)
       .add(unscheduleTask);
   }
-
-  private unscheduleTask() {
-    // maybe this is a race condition, invoke in a timeout
-    // hold for 10ms while I try to figure out what is going on
-    setTimeout(() => {
-      if (this.task != null && this.task.state === "scheduled") {
-        this.task.invoke();
-        this.task = null;
-      }
-    }, 10);
-  }
 }
 
 @Injectable({
@@ -90,6 +83,7 @@ class BlockUntilFirstOperator<T> implements Operator<T, T> {
 export class ɵAngularFireSchedulers {
   public readonly outsideAngular: ɵZoneScheduler;
   public readonly insideAngular: ɵZoneScheduler;
+  public readonly pendingTasks = inject(ExperimentalPendingTasks);
 
   constructor(public ngZone: NgZone) {
     // @ts-ignore
@@ -149,7 +143,9 @@ export function ɵkeepUnstableUntilFirstFactory(
   return function keepUnstableUntilFirst<T>(
     obs$: Observable<T>
   ): Observable<T> {
-    obs$ = obs$.lift(new BlockUntilFirstOperator(schedulers.ngZone));
+    obs$ = obs$.lift(
+      new BlockUntilFirstOperator(schedulers.ngZone, schedulers.pendingTasks)
+    );
 
     return obs$.pipe(
       // Run the subscribe body outside of Angular (e.g. calling Firebase SDK to add a listener to a change event)
@@ -165,19 +161,15 @@ export function ɵkeepUnstableUntilFirstFactory(
 // @ts-ignore
 const zoneWrapFn = (
   it: (...args: any[]) => any,
-  macrotask: MacroTask | undefined
+  taskDone: VoidFunction | undefined
 ) => {
   // eslint-disable-next-line @typescript-eslint/no-this-alias
   const _this = this;
   // function() is needed for the arguments object
   return function () {
     const _arguments = arguments;
-    if (macrotask) {
-      setTimeout(() => {
-        if (macrotask.state === "scheduled") {
-          macrotask.invoke();
-        }
-      }, 10);
+    if (taskDone) {
+      setTimeout(taskDone, 10);
     }
     return run(() => it.apply(_this, _arguments));
   };
@@ -187,26 +179,18 @@ export const ɵzoneWrap = <T = unknown>(it: T, blockUntilFirst: boolean): T => {
   // function() is needed for the arguments object
   return function () {
     // @ts-ignore
-    let macrotask: MacroTask | undefined;
+    let taskDone: VoidFunction | undefined;
     const _arguments = arguments;
-    // if this is a callback function, e.g, onSnapshot, we should create a microtask and invoke it
+    // if this is a callback function, e.g, onSnapshot, we should create a pending task and complete it
     // only once one of the callback functions is tripped.
     for (let i = 0; i < arguments.length; i++) {
       if (typeof _arguments[i] === "function") {
         if (blockUntilFirst) {
           // @ts-ignore
-          macrotask ||= run(() =>
-            Zone.current.scheduleMacroTask(
-              "firebaseZoneBlock",
-              noop,
-              {},
-              noop,
-              noop
-            )
-          );
+          taskDone ||= run(() => getSchedulers().pendingTasks.add());
         }
         // TODO create a microtask to track callback functions
-        _arguments[i] = zoneWrapFn(_arguments[i], macrotask);
+        _arguments[i] = zoneWrapFn(_arguments[i], taskDone);
       }
     }
     const ret = runOutsideAngular(() => (it as any).apply(this, _arguments));
@@ -234,15 +218,11 @@ export const ɵzoneWrap = <T = unknown>(it: T, blockUntilFirst: boolean): T => {
             )
           )
       );
-    } else if (typeof ret === "function" && macrotask) {
+    } else if (typeof ret === "function" && taskDone) {
       // Handle unsubscribe
       // function() is needed for the arguments object
       return function () {
-        setTimeout(() => {
-          if (macrotask && macrotask.state === "scheduled") {
-            macrotask.invoke();
-          }
-        }, 10);
+        setTimeout(taskDone, 10);
         return ret.apply(this, arguments);
       };
     } else {