refactor(service-worker): make `SwTestHarness.envIsSupported()` a standalone function (#42736)

This commit makes the `SwTestHarness.envIsSupported()` static method a
standalone function. This function is used to determine whether the
current environment provides the necessary APIs to run the SW tests and
is independent of `SwTestHarness`, so is no need for it to be a static
method of `SwTestHarness`.

This is in preparation of switching from our custom typings to the
official TypeScript typings (`lib.webworker.d.ts`).

PR Close #42736

packages/service-worker/test/integration_spec.ts

@@ -16,12 +16,13 @@ import {Manifest} from '@angular/service-worker/worker/src/manifest';
 import {MockRequest} from '@angular/service-worker/worker/testing/fetch';
 import {MockFileSystemBuilder, MockServerStateBuilder, tmpHashTableForFs} from '@angular/service-worker/worker/testing/mock';
 import {SwTestHarness, SwTestHarnessBuilder} from '@angular/service-worker/worker/testing/scope';
+import {envIsSupported} from '@angular/service-worker/worker/testing/utils';
 import {Observable} from 'rxjs';
 import {take} from 'rxjs/operators';
 
 (function() {
 // Skip environments that don't support the minimum APIs needed to run the SW tests.
-if (!SwTestHarness.envIsSupported()) {
+if (!envIsSupported()) {
   return;
 }
 

packages/service-worker/worker/test/data_spec.ts

@@ -13,10 +13,11 @@ import {MockCache} from '../testing/cache';
 import {MockRequest} from '../testing/fetch';
 import {MockFileSystemBuilder, MockServerStateBuilder, tmpHashTableForFs} from '../testing/mock';
 import {SwTestHarness, SwTestHarnessBuilder} from '../testing/scope';
+import {envIsSupported} from '../testing/utils';
 
 (function() {
 // Skip environments that don't support the minimum APIs needed to run the SW tests.
-if (!SwTestHarness.envIsSupported()) {
+if (!envIsSupported()) {
   return;
 }
 

packages/service-worker/worker/test/happy_spec.ts

@@ -15,10 +15,11 @@ import {clearAllCaches, MockCache} from '../testing/cache';
 import {MockRequest, MockResponse} from '../testing/fetch';
 import {MockFileSystem, MockFileSystemBuilder, MockServerState, MockServerStateBuilder, tmpHashTableForFs} from '../testing/mock';
 import {MockClient, SwTestHarness, SwTestHarnessBuilder, WindowClientImpl} from '../testing/scope';
+import {envIsSupported} from '../testing/utils';
 
 (function() {
 // Skip environments that don't support the minimum APIs needed to run the SW tests.
-if (!SwTestHarness.envIsSupported()) {
+if (!envIsSupported()) {
   return;
 }
 

packages/service-worker/worker/test/idle_spec.ts

@@ -8,10 +8,11 @@
 
 import {IdleScheduler} from '../src/idle';
 import {SwTestHarness, SwTestHarnessBuilder} from '../testing/scope';
+import {envIsSupported} from '../testing/utils';
 
 (function() {
 // Skip environments that don't support the minimum APIs needed to run the SW tests.
-if (!SwTestHarness.envIsSupported()) {
+if (!envIsSupported()) {
   return;
 }
 

packages/service-worker/worker/test/prefetch_spec.ts

@@ -12,11 +12,12 @@ import {IdleScheduler} from '../src/idle';
 import {MockCache} from '../testing/cache';
 import {MockRequest} from '../testing/fetch';
 import {MockFileSystemBuilder, MockServerStateBuilder, tmpHashTable, tmpManifestSingleAssetGroup} from '../testing/mock';
-import {MockExtendableEvent, SwTestHarness, SwTestHarnessBuilder} from '../testing/scope';
+import {MockExtendableEvent, SwTestHarnessBuilder} from '../testing/scope';
+import {envIsSupported} from '../testing/utils';
 
 (function() {
 // Skip environments that don't support the minimum APIs needed to run the SW tests.
-if (!SwTestHarness.envIsSupported()) {
+if (!envIsSupported()) {
   return;
 }
 

packages/service-worker/worker/testing/scope.ts

@@ -132,22 +132,6 @@ export class SwTestHarness extends Adapter<MockCacheStorage> implements ServiceW
         },
   } as any;
 
-  static envIsSupported(): boolean {
-    if (typeof URL === 'function') {
-      return true;
-    }
-
-    // If we're in a browser that doesn't support URL at this point, don't go any further
-    // since browser builds use requirejs which will fail on the `require` call below.
-    if (typeof window !== 'undefined' && window) {
-      return false;
-    }
-
-    // In older Node.js versions, the `URL` global does not exist. We can use `url` instead.
-    const url = (typeof require === 'function') && require('url');
-    return url && (typeof url.parse === 'function') && (typeof url.resolve === 'function');
-  }
-
   get time() {
     return this.mockTime;
   }

packages/service-worker/worker/testing/utils.ts

@@ -9,6 +9,27 @@
 import {NormalizedUrl} from '../src/api';
 
 
+/**
+ * Determine whether the current environment provides all necessary APIs to run ServiceWorker tests.
+ *
+ * @return Whether ServiceWorker tests can be run in the current environment.
+ */
+export function envIsSupported(): boolean {
+  if (typeof URL === 'function') {
+    return true;
+  }
+
+  // If we're in a browser that doesn't support URL at this point, don't go any further
+  // since browser builds use requirejs which will fail on the `require` call below.
+  if (typeof window !== 'undefined' && window) {
+    return false;
+  }
+
+  // In older Node.js versions, the `URL` global does not exist. We can use `url` instead.
+  const url = (typeof require === 'function') && require('url');
+  return url && (typeof url.parse === 'function') && (typeof url.resolve === 'function');
+}
+
 /**
  * Get a normalized representation of a URL relative to a provided base URL.
  *