feat(service-worker): allow configuring when the SW is registered (#21842)

Fixes #20970

PR Close #21842

aio/content/guide/service-worker-config.md

@@ -218,3 +218,15 @@ If the field is omitted, it defaults to:
   '!/**/*__*/**',  // Exclude URLs containing `__` in any other segment.
 ]
 ```
+
+## `register options`
+
+<code-example path="service-worker-getting-started/src/app/app.module.ts" linenums="false" header="src/app/app.module.ts" region="sw-module"> </code-example>
+ You can pass some options to the `register()` method.
+- enabled: optional parameter, by default is true, if enabled is false, the module will behave like the browser not support service worker, and service worker will not be registered.
+- scope: optional parameter, to specify the subset of your content that you want the service worker to control.
+- registrationStrategy: optional parameter, specify a strategy that determines when to register the service worker, the available options are:
+  - registerWhenStable: this is the default behavior, the service worker will register when the application is stable (no microTasks or macroTasks remain).
+  - registerImmediately: register immediately without waiting the application to become stable.
+  - registerDelay:timeout : register after the timeout period, `timeout` is the number of milliseconds to delay registration. For example `registerDelay:5000` would register the service worker after 5 seconds. If the number of `timeout` is not given (`registerDelay`), by default, `timeout` will be `0`, but it is not equal to `registerImmediately`, it will still run a `setTimeout(register, 0)` to wait all `microTasks` to finish then perform registration of the service worker.
+  - A factory to get Observable : you can also specify a factory which returns an Observable, the service worker will be registered the first time that a value is emitted by the Observable.

aio/content/guide/service-worker-getting-started.md

@@ -1,7 +1,7 @@
 # Getting started with service workers
 
 
-This document explains how to enable Angular service worker support in projects that you created with the [Angular CLI](cli). It then uses a simple example to show you a service worker in action, demonstrating loading and basic caching. 
+This document explains how to enable Angular service worker support in projects that you created with the [Angular CLI](cli). It then uses a simple example to show you a service worker in action, demonstrating loading and basic caching.
 
 #### Prerequisites
 
@@ -10,26 +10,26 @@ A basic understanding of the information in [Introduction to Angular service wor
 
 ## Adding a service worker to your project
 
-To set up the Angular service worker in your project, use the CLI command `ng add @angular/pwa`. It takes care of configuring your app to use service workers by adding the `service-worker` package along 
+To set up the Angular service worker in your project, use the CLI command `ng add @angular/pwa`. It takes care of configuring your app to use service workers by adding the `service-worker` package along
 with setting up the necessary support files.
 
 ```sh
-ng add @angular/pwa --project *project-name* 
+ng add @angular/pwa --project *project-name*
 ```
 
 The above command completes the following actions:
 
-1. Adds the `@angular/service-worker` package to your project. 
+1. Adds the `@angular/service-worker` package to your project.
 2. Enables service worker build support in the CLI.
 3. Imports and registers the service worker in the app module.
 4. Updates the `index.html` file:
     * Includes a link to add the `manifest.json` file.
     * Adds meta tags for `theme-color`.
 5. Installs icon files to support the installed Progressive Web App (PWA).
-6. Creates the service worker configuration file called [`ngsw-config.json`](/guide/service-worker-config), which specifies the caching behaviors and other settings. 
+6. Creates the service worker configuration file called [`ngsw-config.json`](/guide/service-worker-config), which specifies the caching behaviors and other settings.
 
 
- Now, build the project: 
+ Now, build the project:
 
 ```sh
 ng build --prod
@@ -40,8 +40,8 @@ The CLI project is now set up to use the Angular service worker.
 
 ## Service worker in action: a tour
 
-This section demonstrates a service worker in action, 
+This section demonstrates a service worker in action,
-using an example application. 
+using an example application.
 
 ### Serving with `http-server`
 
@@ -61,7 +61,7 @@ With the server running, you can point your browser at http://localhost:8080/. Y
 
 ### Simulating a network issue
 
-To simulate a network issue, disable network interaction for your application. In Chrome: 
+To simulate a network issue, disable network interaction for your application. In Chrome:
 
 1. Select **Tools** > **Developer Tools** (from the Chrome menu located at the top right corner).
 2. Go to the **Network tab**.
@@ -73,9 +73,9 @@ To simulate a network issue, disable network interaction for your application. I
 
 Now the app has no access to network interaction.
 
-For applications that do not use the Angular service worker, refreshing now would display Chrome's Internet disconnected page that says "There is no Internet connection". 
+For applications that do not use the Angular service worker, refreshing now would display Chrome's Internet disconnected page that says "There is no Internet connection".
 
-With the addition of an Angular service worker, the application behavior changes. On a refresh, the page loads normally. 
+With the addition of an Angular service worker, the application behavior changes. On a refresh, the page loads normally.
 
 If you look at the Network tab, you can verify that the service worker is active.
 
@@ -107,12 +107,12 @@ Pay attention to two key points:
 
 ### Making changes to your application
 
-Now that you've seen how service workers cache your application, the 
+Now that you've seen how service workers cache your application, the
-next step is understanding how updates work. 
+next step is understanding how updates work.
 
 1. If you're testing in an incognito window, open a second blank tab. This will keep the incognito and the cache state alive during your test.
 
-2. Close the application tab, but not the window. This should also close the Developer Tools. 
+2. Close the application tab, but not the window. This should also close the Developer Tools.
 
 3. Shut down `http-server`.
 
@@ -156,4 +156,4 @@ The service worker installed the updated version of your app *in the background*
 ## More on Angular service workers
 
 You may also be interested in the following:
-* [Communicating with service workers](guide/service-worker-communications).
+* [Communicating with service workers](guide/service-worker-communications).

packages/service-worker/src/module.ts

@@ -8,6 +8,7 @@
 
 import {isPlatformBrowser} from '@angular/common';
 import {APP_INITIALIZER, ApplicationRef, InjectionToken, Injector, ModuleWithProviders, NgModule, PLATFORM_ID} from '@angular/core';
+import {Observable} from 'rxjs';
 import {filter, take} from 'rxjs/operators';
 
 import {NgswCommChannel} from './low_level';
@@ -41,6 +42,8 @@ export abstract class SwRegistrationOptions {
    * [ServiceWorkerContainer#register()](https://developer.mozilla.org/en-US/docs/Web/API/ServiceWorkerContainer/register).
    */
   scope?: string;
+
+  registrationStrategy?: (() => Observable<any>)|string;
 }
 
 export const SCRIPT = new InjectionToken<string>('NGSW_REGISTER_SCRIPT');
@@ -68,7 +71,33 @@ export function ngswAppInitializer(
 
     // Don't return the Promise, as that will block the application until the SW is registered, and
     // cause a crash if the SW registration fails.
-    whenStable.then(() => navigator.serviceWorker.register(script, {scope: options.scope}));
+    if (typeof options.registrationStrategy === 'function') {
+      const observable = options.registrationStrategy();
+      const subscription = observable.subscribe(() => {
+        navigator.serviceWorker.register(script, {scope: options.scope});
+        subscription.unsubscribe();
+      });
+    } else {
+      const registrationStrategy = typeof options.registrationStrategy === 'string' ?
+          options.registrationStrategy :
+          'registerWhenStable';
+      if (registrationStrategy === 'registerWhenStable') {
+        whenStable.then(() => navigator.serviceWorker.register(script, {scope: options.scope}));
+      } else if (registrationStrategy === 'registerImmediately') {
+        navigator.serviceWorker.register(script, {scope: options.scope});
+      } else if (registrationStrategy.indexOf('registerDelay') !== -1) {
+        const split = registrationStrategy.split(':');
+        const delayStr = split.length > 1 ? split[1] : undefined;
+        const delay = Number(delayStr);
+        setTimeout(
+            () => navigator.serviceWorker.register(script, {scope: options.scope}),
+            typeof delay === 'number' ? delay : 0);
+      } else {
+        // wrong strategy
+        throw new Error(
+            `Unknown service worker registration strategy: ${options.registrationStrategy}`);
+      }
+    }
   };
   return initializer;
 }

tools/public_api_guard/service-worker/service-worker.d.ts

@@ -21,6 +21,7 @@ export declare class SwPush {
 
 export declare abstract class SwRegistrationOptions {
     enabled?: boolean;
+    registrationStrategy?: (() => Observable<any>) | string;
     scope?: string;
 }