feat(store): make reducers accessible from ReducerManager (#3064)

* feat(reducer-manager): permit to access reducers

* ref: rename reducerSnapshot to currentReducers

* test: apply check if getter for currentReducers works as expected

modules/store/spec/reducer_manager.spec.ts

@@ -0,0 +1,35 @@
+import { TestBed } from '@angular/core/testing';
+import { createReducer, ReducerManager, StoreModule } from '@ngrx/store';
+
+describe(ReducerManager.name, () => {
+  it('should provide reducers being registered in store', () => {
+    TestBed.configureTestingModule({
+      imports: [
+        StoreModule.forRoot({
+          'feature-1': createReducer(0),
+        }),
+      ],
+    });
+
+    const reducerManager = TestBed.inject(ReducerManager);
+
+    expect(Object.keys(reducerManager.currentReducers)).toContain('feature-1');
+  });
+
+  it('should provide reducers being registered at runtime', () => {
+    TestBed.configureTestingModule({
+      imports: [
+        StoreModule.forRoot({
+          'feature-1': createReducer(0),
+        }),
+      ],
+    });
+
+    const reducerManager = TestBed.inject(ReducerManager);
+
+    reducerManager.addReducer('feature-2', createReducer(0));
+
+    expect(Object.keys(reducerManager.currentReducers)).toContain('feature-1');
+    expect(Object.keys(reducerManager.currentReducers)).toContain('feature-2');
+  });
+});

modules/store/src/reducer_manager.ts

@@ -1,6 +1,5 @@
 import { Inject, Injectable, OnDestroy, Provider } from '@angular/core';
 import { BehaviorSubject, Observable } from 'rxjs';
-
 import { ActionsSubject } from './actions_subject';
 import {
   Action,
@@ -26,6 +25,10 @@ export const UPDATE = '@ngrx/store/update-reducers' as const;
 export class ReducerManager
   extends BehaviorSubject<ActionReducer<any, any>>
   implements OnDestroy {
+  get currentReducers(): ActionReducerMap<any, any> {
+    return this.reducers;
+  }
+
   constructor(
     private dispatcher: ReducerManagerDispatcher,
     @Inject(INITIAL_STATE) private initialState: any,