refactor(upgrade): extract promise-related utilities to separate file and add tests (#31840)

PR Close #31840

packages/upgrade/src/common/src/downgrade_component.ts

@@ -11,13 +11,10 @@ import {ComponentFactory, ComponentFactoryResolver, Injector, NgZone, Type} from
 import {IAnnotatedFunction, IAttributes, IAugmentedJQuery, ICompileService, IDirective, IInjectorService, INgModelController, IParseService, IScope} from './angular1';
 import {$COMPILE, $INJECTOR, $PARSE, INJECTOR_KEY, LAZY_MODULE_REF, REQUIRE_INJECTOR, REQUIRE_NG_MODEL} from './constants';
 import {DowngradeComponentAdapter} from './downgrade_component_adapter';
-import {LazyModuleRef, UpgradeAppType, controllerKey, getDowngradedModuleCount, getTypeName, getUpgradeAppType, isFunction, validateInjectionKey} from './util';
+import {SyncPromise, Thenable, isThenable} from './promise_util';
+import {LazyModuleRef, UpgradeAppType, controllerKey, getDowngradedModuleCount, getTypeName, getUpgradeAppType, validateInjectionKey} from './util';
 
 
-interface Thenable<T> {
-  then(callback: (value: T) => any): any;
-}
-
 /**
  * @description
  *
@@ -218,42 +215,26 @@ export function downgradeComponent(info: {
 
 /**
  * Synchronous promise-like object to wrap parent injectors,
- * to preserve the synchronous nature of Angular 1's $compile.
+ * to preserve the synchronous nature of AngularJS's `$compile`.
  */
-class ParentInjectorPromise {
-  // TODO(issue/24571): remove '!'.
-  private injector !: Injector;
+class ParentInjectorPromise extends SyncPromise<Injector> {
   private injectorKey: string = controllerKey(INJECTOR_KEY);
-  private callbacks: ((injector: Injector) => any)[] = [];
 
   constructor(private element: IAugmentedJQuery) {
+    super();
+
     // Store the promise on the element.
     element.data !(this.injectorKey, this);
   }
 
-  then(callback: (injector: Injector) => any) {
-    if (this.injector) {
-      callback(this.injector);
-    } else {
-      this.callbacks.push(callback);
-    }
-  }
-
-  resolve(injector: Injector) {
-    this.injector = injector;
-
+  resolve(injector: Injector): void {
     // Store the real injector on the element.
     this.element.data !(this.injectorKey, injector);
 
     // Release the element to prevent memory leaks.
     this.element = null !;
 
-    // Run the queued callbacks.
-    this.callbacks.forEach(callback => callback(injector));
-    this.callbacks.length = 0;
+    // Resolve the promise.
+    super.resolve(injector);
   }
 }
-
-function isThenable<T>(obj: object): obj is Thenable<T> {
-  return isFunction((obj as any).then);
-}

packages/upgrade/src/common/src/promise_util.ts

@@ -0,0 +1,44 @@
+/**
+ * @license
+ * Copyright Google Inc. All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+import {isFunction} from './util';
+
+export interface Thenable<T> { then(callback: (value: T) => any): any; }
+
+export function isThenable<T>(obj: unknown): obj is Thenable<T> {
+  return !!obj && isFunction((obj as any).then);
+}
+
+/**
+ * Synchronous, promise-like object.
+ */
+export class SyncPromise<T> {
+  protected value: T|undefined;
+  private resolved = false;
+  private callbacks: ((value: T) => unknown)[] = [];
+
+  resolve(value: T): void {
+    // Do nothing, if already resolved.
+    if (this.resolved) return;
+
+    this.value = value;
+    this.resolved = true;
+
+    // Run the queued callbacks.
+    this.callbacks.forEach(callback => callback(value));
+    this.callbacks.length = 0;
+  }
+
+  then(callback: (value: T) => unknown): void {
+    if (this.resolved) {
+      callback(this.value !);
+    } else {
+      this.callbacks.push(callback);
+    }
+  }
+}

packages/upgrade/src/common/test/promise_util_spec.ts

@@ -0,0 +1,88 @@
+/**
+ * @license
+ * Copyright Google Inc. All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+import {SyncPromise, isThenable} from '../src/promise_util';
+
+describe('isThenable()', () => {
+  it('should return false for primitive values', () => {
+    expect(isThenable(undefined)).toBe(false);
+    expect(isThenable(null)).toBe(false);
+    expect(isThenable(false)).toBe(false);
+    expect(isThenable(true)).toBe(false);
+    expect(isThenable(0)).toBe(false);
+    expect(isThenable(1)).toBe(false);
+    expect(isThenable('')).toBe(false);
+    expect(isThenable('foo')).toBe(false);
+  });
+
+  it('should return false if `.then` is not a function', () => {
+    expect(isThenable([])).toBe(false);
+    expect(isThenable(['then'])).toBe(false);
+    expect(isThenable(function() {})).toBe(false);
+    expect(isThenable({})).toBe(false);
+    expect(isThenable({then: true})).toBe(false);
+    expect(isThenable({then: 'not a function'})).toBe(false);
+
+  });
+
+  it('should return true if `.then` is a function', () => {
+    expect(isThenable({then: function() {}})).toBe(true);
+    expect(isThenable({then: () => {}})).toBe(true);
+    expect(isThenable(Object.assign('thenable', {then: () => {}}))).toBe(true);
+  });
+});
+
+describe('SyncPromise', () => {
+  it('should call all callbacks once resolved', () => {
+    const spy1 = jasmine.createSpy('spy1');
+    const spy2 = jasmine.createSpy('spy2');
+
+    const promise = new SyncPromise<string>();
+    promise.then(spy1);
+    promise.then(spy2);
+
+    expect(spy1).not.toHaveBeenCalled();
+    expect(spy2).not.toHaveBeenCalled();
+
+    promise.resolve('foo');
+
+    expect(spy1).toHaveBeenCalledWith('foo');
+    expect(spy2).toHaveBeenCalledWith('foo');
+  });
+
+  it('should call callbacks immediately if already resolved', () => {
+    const spy = jasmine.createSpy('spy');
+
+    const promise = new SyncPromise<string>();
+    promise.resolve('foo');
+    promise.then(spy);
+
+    expect(spy).toHaveBeenCalledWith('foo');
+  });
+
+  it('should ignore subsequent calls to `resolve()`', () => {
+    const spy = jasmine.createSpy('spy');
+
+    const promise = new SyncPromise<string>();
+
+    promise.then(spy);
+    promise.resolve('foo');
+    expect(spy).toHaveBeenCalledWith('foo');
+
+    spy.calls.reset();
+
+    promise.resolve('bar');
+    expect(spy).not.toHaveBeenCalled();
+
+    promise.then(spy);
+    promise.resolve('baz');
+
+    expect(spy).toHaveBeenCalledTimes(1);
+    expect(spy).toHaveBeenCalledWith('foo');
+  });
+});