Ps/sync only when changed (#4245)

* Only sync if synced value changes

Co-authored-by: Daniel James Smith <djsmith85@users.noreply.github.com>

* Catch error if no one is listening

This occurs if the background tries to update any visualizers, but none
are open.

Co-authored-by: Daniel James Smith <djsmith85@users.noreply.github.com>
Co-authored-by: Justin Baur <justindbaur@users.noreply.github.com>

* Allow provided deserializer to handle not found

* Debounce synced items

* Remove object-hash

* Revert "Only sync if synced value changes"

This reverts commit 024fe226d9.

* Test debounce

Co-authored-by: Daniel James Smith <djsmith85@users.noreply.github.com>
Co-authored-by: Justin Baur <justindbaur@users.noreply.github.com>
Co-authored-by: Justin Baur <19896123+justindbaur@users.noreply.github.com>

apps/browser/src/decorators/session-sync-observable/session-syncer.spec.ts

@@ -32,6 +32,7 @@ describe("session syncer", () => {
     stateService = mock<BrowserStateService>();
     stateService.hasInSessionMemory.mockResolvedValue(false);
     sut = new SessionSyncer(behaviorSubject, stateService, metaData);
+    jest.spyOn(sut as any, "debounceMs", "get").mockReturnValue(0);
   });
 
   afterEach(() => {
@@ -88,7 +89,7 @@ describe("session syncer", () => {
 
       sut.init();
 
-      expect(sut["ignoreNUpdates"]).toBe(3);
+      expect(sut["ignoreNUpdates"]).toBe(1);
     });
 
     it("should ignore BehaviorSubject's initial value", () => {
@@ -128,28 +129,41 @@ describe("session syncer", () => {
   describe("a value is emitted on the observable", () => {
     let sendMessageSpy: jest.SpyInstance;
 
-    beforeEach(() => {
+    beforeEach(async () => {
       sendMessageSpy = jest.spyOn(BrowserApi, "sendMessage");
 
       sut.init();
 
+      // allow initial value to be set
+      await awaitAsync();
       behaviorSubject.next("test");
     });
 
     it("should update the session memory", async () => {
       // await finishing of fire-and-forget operation
-      await new Promise((resolve) => setTimeout(resolve, 100));
+      await awaitAsync();
       expect(stateService.setInSessionMemory).toHaveBeenCalledTimes(1);
       expect(stateService.setInSessionMemory).toHaveBeenCalledWith(sessionKey, "test");
     });
 
     it("should update sessionSyncers in other contexts", async () => {
       // await finishing of fire-and-forget operation
-      await new Promise((resolve) => setTimeout(resolve, 100));
+      await awaitAsync();
 
       expect(sendMessageSpy).toHaveBeenCalledTimes(1);
       expect(sendMessageSpy).toHaveBeenCalledWith(`${sessionKey}_update`, { id: sut.id });
     });
+
+    it("should debounce subject updates", async () => {
+      behaviorSubject.next("test2");
+      behaviorSubject.next("test3");
+
+      // await finishing of fire-and-forget operation
+      await awaitAsync();
+
+      expect(stateService.setInSessionMemory).toHaveBeenCalledTimes(1);
+      expect(stateService.setInSessionMemory).toHaveBeenCalledWith(sessionKey, "test3");
+    });
   });
 
   describe("A message is received", () => {

apps/browser/src/decorators/session-sync-observable/session-syncer.ts

@@ -1,4 +1,11 @@
-import { BehaviorSubject, concatMap, ReplaySubject, Subject, Subscription } from "rxjs";
+import {
+  BehaviorSubject,
+  concatMap,
+  ReplaySubject,
+  Subject,
+  Subscription,
+  debounceTime,
+} from "rxjs";
 
 import { Utils } from "@bitwarden/common/misc/utils";
 
@@ -13,6 +20,9 @@ export class SessionSyncer {
 
   // ignore initial values
   private ignoreNUpdates = 0;
+  private get debounceMs() {
+    return 500;
+  }
 
   constructor(
     private subject: Subject<any>,
@@ -30,10 +40,8 @@ export class SessionSyncer {
 
   init() {
     switch (this.subject.constructor) {
-      case ReplaySubject:
-        // ignore all updates currently in the buffer
-        this.ignoreNUpdates = (this.subject as any)._buffer.length;
-        break;
+      // ignore all updates currently in the buffer
+      case ReplaySubject: // N = 1 due to debounce
       case BehaviorSubject:
         this.ignoreNUpdates = 1;
         break;
@@ -58,6 +66,7 @@ export class SessionSyncer {
     // contexts. If so, this is handled by destruction of the context.
     this.subscription = this.subject
       .pipe(
+        debounceTime(this.debounceMs),
         concatMap(async (next) => {
           if (this.ignoreNUpdates > 0) {
             this.ignoreNUpdates -= 1;
@@ -92,8 +101,15 @@ export class SessionSyncer {
   }
 
   private async updateSession(value: any) {
-    await this.stateService.setInSessionMemory(this.metaData.sessionKey, value);
-    await BrowserApi.sendMessage(this.updateMessageCommand, { id: this.id });
+    try {
+      await this.stateService.setInSessionMemory(this.metaData.sessionKey, value);
+      await BrowserApi.sendMessage(this.updateMessageCommand, { id: this.id });
+    } catch (e) {
+      if (e.message === "Could not establish connection. Receiving end does not exist.") {
+        return;
+      }
+      throw e;
+    }
   }
 
   private get updateMessageCommand() {