Replace MessageModel#isUnread with isMessageUnread utility

ts/messageModifiers/ReadSyncs.ts

@@ -7,6 +7,7 @@ import { Collection, Model } from 'backbone';
 
 import { MessageModel } from '../models/messages';
 import { isIncoming } from '../state/selectors/message';
+import { isMessageUnread } from '../util/isMessageUnread';
 
 type ReadSyncAttributesType = {
   senderId: string;
@@ -109,7 +110,7 @@ export class ReadSyncs extends Collection {
       // If message is unread, we mark it read. Otherwise, we update the expiration
       //   timer to the time specified by the read sync if it's earlier than
       //   the previous read time.
-      if (message.isUnread()) {
+      if (isMessageUnread(message.attributes)) {
         // TODO DESKTOP-1509: use MessageUpdater.markRead once this is TS
         message.markRead(readAt, { skipSave: true });
 

ts/models/messages.ts

@@ -56,6 +56,7 @@ import {
 import { migrateLegacySendAttributes } from '../messages/migrateLegacySendAttributes';
 import { getOwn } from '../util/getOwn';
 import { markRead } from '../services/MessageUpdater';
+import { isMessageUnread } from '../util/isMessageUnread';
 import {
   isDirectConversation,
   isGroupV1,
@@ -745,10 +746,6 @@ export class MessageModel extends window.Backbone.Model<MessageAttributesType> {
     }
   }
 
-  isUnread(): boolean {
-    return !!this.get('unread');
-  }
-
   merge(model: MessageModel): void {
     const attributes = model.attributes || model;
     this.set(attributes);
@@ -847,7 +844,7 @@ export class MessageModel extends window.Backbone.Model<MessageAttributesType> {
       return;
     }
 
-    if (this.get('unread')) {
+    if (isMessageUnread(this.attributes)) {
       this.set(markRead(this.attributes));
     }
 
@@ -3175,7 +3172,7 @@ export class MessageModel extends window.Backbone.Model<MessageAttributesType> {
     const isFirstRun = false;
     await this.modifyTargetMessage(conversation, isFirstRun);
 
-    if (this.get('unread')) {
+    if (isMessageUnread(this.attributes)) {
       await conversation.notify(this);
     }
 

ts/state/ducks/conversations.ts

@@ -47,6 +47,7 @@ import {
   getGroupSizeRecommendedLimit,
   getGroupSizeHardLimit,
 } from '../../groups/limits';
+import { isMessageUnread } from '../../util/isMessageUnread';
 import { toggleSelectedContactForGroupAddition } from '../../groups/toggleSelectedContactForGroupAddition';
 import { GroupNameCollisionsWithIdsByTitle } from '../../util/groupMemberNameCollisions';
 import { ContactSpoofingType } from '../../util/contactSpoofing';
@@ -2241,7 +2242,7 @@ export function reducer(
       const oldestId = newMessageIds.find(messageId => {
         const message = lookup[messageId];
 
-        return Boolean(message.unread);
+        return message && isMessageUnread(message);
       });
 
       if (oldestId) {
@@ -2257,7 +2258,7 @@ export function reducer(
       const newUnread: number = newMessageIds.reduce((sum, messageId) => {
         const message = lookup[messageId];
 
-        return sum + (message && message.unread ? 1 : 0);
+        return sum + (message && isMessageUnread(message) ? 1 : 0);
       }, 0);
       totalUnread = (totalUnread || 0) + newUnread;
     }

ts/test-both/util/isMessageUnread_test.ts

@@ -0,0 +1,21 @@
+// Copyright 2021 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import { assert } from 'chai';
+
+import { isMessageUnread } from '../../util/isMessageUnread';
+
+describe('isMessageUnread', () => {
+  it("returns false if the message's `unread` field is undefined", () => {
+    assert.isFalse(isMessageUnread({}));
+    assert.isFalse(isMessageUnread({ unread: undefined }));
+  });
+
+  it('returns false if the message is read', () => {
+    assert.isFalse(isMessageUnread({ unread: false }));
+  });
+
+  it('returns true if the message is unread', () => {
+    assert.isTrue(isMessageUnread({ unread: true }));
+  });
+});

ts/util/isMessageUnread.ts

@@ -0,0 +1,8 @@
+// Copyright 2021 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import type { MessageAttributesType } from '../model-types.d';
+
+export const isMessageUnread = (
+  message: Readonly<Pick<MessageAttributesType, 'unread'>>
+): boolean => Boolean(message.unread);

ts/views/conversation_view.ts

@@ -40,6 +40,7 @@ import {
   isOutgoing,
   isTapToView,
 } from '../state/selectors/message';
+import { isMessageUnread } from '../util/isMessageUnread';
 import { getMessagesByConversation } from '../state/selectors/conversations';
 import { ConversationDetailsMembershipList } from '../components/conversation/conversation-details/ConversationDetailsMembershipList';
 import { showSafetyNumberChangeDialog } from '../shims/showSafetyNumberChangeDialog';
@@ -1313,17 +1314,17 @@ Whisper.ConversationView = Whisper.View.extend({
         const newestInMemoryMessage = await getMessageById(newestMessageId, {
           Message: Whisper.Message,
         });
-        if (!newestInMemoryMessage) {
+        if (newestInMemoryMessage) {
+          // If newest in-memory message is unread, scrolling down would mean going to
+          //   the very bottom, not the oldest unread.
+          if (isMessageUnread(newestInMemoryMessage.attributes)) {
+            scrollToLatestUnread = false;
+          }
+        } else {
           window.log.warn(
             `loadNewestMessages: did not find message ${newestMessageId}`
           );
         }
-
-        // If newest in-memory message is unread, scrolling down would mean going to
-        //   the very bottom, not the oldest unread.
-        if (newestInMemoryMessage && newestInMemoryMessage.isUnread()) {
-          scrollToLatestUnread = false;
-        }
       }
 
       const metrics = await getMessageMetricsForConversation(conversationId);