feat(core): add allOf operator (#2517)

libs/core/src/operators/all-of.pipe.spec.ts

@@ -0,0 +1,22 @@
+import {
+  cold,
+  hot,
+} from 'jasmine-marbles';
+
+import { allOf } from './all-of.pipe';
+
+describe('@daffodil/core | allOf', () => {
+  it('should return true when all of the input streams emit a truthy value', () => {
+    expect(allOf([
+      hot('ab', { a: true, b: true }),
+      hot('ab', { a: false, b: true }),
+    ])).toBeObservable(cold('a(bc)', { a: false, b: false, c: true }));
+  });
+
+  it('should return false when any of the input streams emit a falsy value', () => {
+    expect(allOf([
+      hot('ab', { a: true, b: false }),
+      hot('ab', { a: false, b: false }),
+    ])).toBeObservable(cold('a(bc)', { a: false, b: false, c: false }));
+  });
+});

libs/core/src/operators/all-of.pipe.ts

@@ -0,0 +1,13 @@
+import {
+  Observable,
+  combineLatest,
+  map,
+} from 'rxjs';
+
+/**
+ * Accepts a list of input observables and emits true when all of the inputs emit a truthy value.
+ * Does not emit until all of the input streams have emitted at least once.
+ */
+export const allOf = (items: Observable<boolean>[]) => combineLatest(items).pipe(map((els) => els.reduce(
+  (agg, el) => agg && el, true)),
+);

libs/core/src/operators/public_api.ts

@@ -1 +1,2 @@
 export * from './backoff.pipe';
+export * from './all-of.pipe';