From 96cdf035d8118a23ca1dc4ca713ad02f93cde8fa Mon Sep 17 00:00:00 2001
From: Alex Wiese <alex@wiese.com.au>
Date: Mon, 24 Feb 2020 12:04:22 +0000
Subject: [PATCH] fix(service-worker): treat 503 as offline (#35595)

Prior to this commit the service worker only treated 504 errors as "effectively offline".
This commit changes the behaviour to treat both 503 (Service Unavailable) and 504 as "offline".

Fixes #35571

PR Close #35595
---
 packages/service-worker/worker/src/driver.ts    |  4 ++--
 .../service-worker/worker/test/happy_spec.ts    | 17 ++++++++++++++++-
 2 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/packages/service-worker/worker/src/driver.ts b/packages/service-worker/worker/src/driver.ts
index 2091bd8d95..fce947b436 100644
--- a/packages/service-worker/worker/src/driver.ts
+++ b/packages/service-worker/worker/src/driver.ts
@@ -684,7 +684,7 @@ export class Driver implements Debuggable, UpdateSource {
   /**
    * Retrieve a copy of the latest manifest from the server.
    * Return `null` if `ignoreOfflineError` is true (default: false) and the server or client are
-   * offline (detected as response status 504).
+   * offline (detected as response status 503 (service unavailable) or 504 (gateway timeout)).
    */
   private async fetchLatestManifest(ignoreOfflineError?: false): Promise<Manifest>;
   private async fetchLatestManifest(ignoreOfflineError: true): Promise<Manifest|null>;
@@ -695,7 +695,7 @@ export class Driver implements Debuggable, UpdateSource {
       if (res.status === 404) {
         await this.deleteAllCaches();
         await this.scope.registration.unregister();
-      } else if (res.status === 504 && ignoreOfflineError) {
+      } else if ((res.status === 503 || res.status === 504) && ignoreOfflineError) {
         return null;
       }
       throw new Error(`Manifest fetch failed! (status: ${res.status})`);
diff --git a/packages/service-worker/worker/test/happy_spec.ts b/packages/service-worker/worker/test/happy_spec.ts
index 2c990cc3a2..adc674bda9 100644
--- a/packages/service-worker/worker/test/happy_spec.ts
+++ b/packages/service-worker/worker/test/happy_spec.ts
@@ -12,7 +12,7 @@ import {Driver, DriverReadyState} from '../src/driver';
 import {AssetGroupConfig, DataGroupConfig, Manifest} from '../src/manifest';
 import {sha1} from '../src/sha1';
 import {MockCache, clearAllCaches} from '../testing/cache';
-import {MockRequest} from '../testing/fetch';
+import {MockRequest, MockResponse} from '../testing/fetch';
 import {MockFileSystemBuilder, MockServerStateBuilder, tmpHashTableForFs} from '../testing/mock';
 import {SwTestHarness, SwTestHarnessBuilder} from '../testing/scope';
 
@@ -872,6 +872,21 @@ import {SwTestHarness, SwTestHarnessBuilder} from '../testing/scope';
       expect(await scope.caches.keys()).not.toEqual([]);
     });
 
+    it('does not unregister or change state when status code is 503 (service unavailable)',
+       async() => {
+         expect(await makeRequest(scope, '/foo.txt')).toEqual('this is foo');
+         await driver.initialized;
+         spyOn(server, 'fetch').and.callFake((req: Request) => new MockResponse(null, {
+                                               status: 503,
+                                               statusText: 'Service Unavailable'
+                                             }));
+
+         expect(await driver.checkForUpdate()).toEqual(false);
+         expect(driver.state).toEqual(DriverReadyState.NORMAL);
+         expect(scope.unregistered).toBeFalsy();
+         expect(await scope.caches.keys()).not.toEqual([]);
+       });
+
     describe('cache naming', () => {
       // Helpers
       const cacheKeysFor = (baseHref: string) =>