refactor(service-worker): avoid unnecessary operations and remove unused code (#24127)

PR Close #24127

packages/service-worker/worker/src/driver.ts

@@ -225,7 +225,9 @@ export class Driver implements Debuggable, UpdateSource {
     // Initialization is the only event which is sent directly from the SW to itself,
     // and thus `event.source` is not a Client. Handle it here, before the check
     // for Client sources.
-    if (data.action === 'INITIALIZE' && this.initialized === null) {
+    if (data.action === 'INITIALIZE') {
+      // Only initialize if not already initialized (or initializing).
+      if (this.initialized === null) {
         // Initialize the SW.
         this.initialized = this.initialize();
 
@@ -237,6 +239,9 @@ export class Driver implements Debuggable, UpdateSource {
         })());
       }
 
+      return;
+    }
+
     // Only messages from true clients are accepted past this point (this is essentially
     // a typecast).
     if (!this.adapter.isClient(event.source)) {
@@ -725,16 +730,6 @@ export class Driver implements Debuggable, UpdateSource {
   private async setupUpdate(manifest: Manifest, hash: string): Promise<void> {
     const newVersion = new AppVersion(this.scope, this.adapter, this.db, this.idle, manifest, hash);
 
-    // Try to determine a version that's safe to update from.
-    let updateFrom: AppVersion|undefined = undefined;
-
-    // It's always safe to update from a version, even a broken one, as it will still
-    // only have valid resources cached. If there is no latest version, though, this
-    // update will have to install as a fresh version.
-    if (this.latestHash !== null) {
-      updateFrom = this.versions.get(this.latestHash);
-    }
-
     // Firstly, check if the manifest version is correct.
     if (manifest.configVersion !== SUPPORTED_CONFIG_VERSION) {
       await this.deleteAllCaches();