FIX: Avoid leaking TopicTrackingState listeners due to sidebar (#18131)

In eb12daa7f8 when adding community
section support for anonymous users, we changed the `sectionLinks`
property into a getter method. This meant that if the getter method was
called again after the community section has been rendered, we would end
up reintializing the section links classes. As part of the
initialisation, some section links would setup a TopicTrackingState
onStateChange listener. However, the listener is only removed when the
entire community section is removed which resulted in us leaking the
onStateChange listeners.

This commit reverts the `sectionLinks` from being defined as a getter
method into a property which is only set once when the community section
is being constructor. Also, we changed it such that the community
section will register the listener instead of each section link since it
makes cleaning up much easier to reason about.

No tests have been added for this commit because the original bug is
not possible after this change and we already have an existing tests
ensuring that TopicTrackingState change listeners are cleaned up when
the community section is destroyed.

Internal ref: /t/73224

app/assets/javascripts/discourse/app/components/sidebar/anonymous/community-section.js

@@ -7,18 +7,16 @@ import UsersSectionLink from "discourse/lib/sidebar/common/community-section/use
 import BadgesSectionLink from "discourse/lib/sidebar/common/community-section/badges-section-link";
 
 export default class SidebarAnonymousCommunitySection extends SidebarCommonCommunitySection {
-  constructor() {
-    super(...arguments);
-
-    this.defaultMoreSectionLinks = [GroupsSectionLink, BadgesSectionLink];
-
-    this.defaultMoreSecondarySectionLinks = [];
-
-    this.defaultMainSectionLinks = [
+  get defaultMainSectionLinks() {
+    return [
       EverythingSectionLink,
       UsersSectionLink,
       AboutSectionLink,
       FAQSectionLink,
     ];
   }
+
+  get defaultMoreSectionLinks() {
+    return [GroupsSectionLink, BadgesSectionLink];
+  }
 }

app/assets/javascripts/discourse/app/components/sidebar/common/community-section.js

@@ -13,45 +13,68 @@ export default class SidebarCommunitySection extends Component {
   @service appEvents;
   @service siteSettings;
 
-  // Override in child
-  defaultMainSectionLinks = [];
-  defaultAdminMainSectionLinks = [];
-  defaultMoreSectionLinks = [];
-  defaultMoreSecondarySectionLinks = [];
   headerActionsIcon;
   headerActions;
+  sectionLinks;
+  moreSectionLinks;
+  moreSecondarySectionLinks;
+  callbackId;
 
-  get moreSectionLinks() {
-    return [...this.defaultMoreSectionLinks, ...customSectionLinks].map(
-      (sectionLinkClass) => {
+  constructor() {
+    super(...arguments);
+
+    this.moreSectionLinks = [
+      ...this.defaultMoreSectionLinks,
+      ...customSectionLinks,
+    ].map((sectionLinkClass) => {
       return this.#initializeSectionLink(sectionLinkClass);
-      }
-    );
-  }
+    });
 
-  get moreSecondarySectionLinks() {
-    return [
+    this.moreSecondarySectionLinks = [
       ...this.defaultMoreSecondarySectionLinks,
       ...secondaryCustomSectionLinks,
     ].map((sectionLinkClass) => {
       return this.#initializeSectionLink(sectionLinkClass);
     });
-  }
 
-  get mainSectionLinks() {
-    return this.currentUser?.staff
+    const mainSectionLinks = this.currentUser?.staff
       ? [...this.defaultMainSectionLinks, ...this.defaultAdminMainSectionLinks]
       : [...this.defaultMainSectionLinks];
-  }
 
-  get sectionLinks() {
-    return this.mainSectionLinks.map((sectionLinkClass) => {
+    this.sectionLinks = mainSectionLinks.map((sectionLinkClass) => {
       return this.#initializeSectionLink(sectionLinkClass);
     });
+
+    this.callbackId = this.topicTrackingState.onStateChange(() => {
+      this.sectionLinks.forEach((sectionLink) => {
+        sectionLink.onTopicTrackingStateChange();
+      });
+    });
   }
 
   willDestroy() {
     this.sectionLinks.forEach((sectionLink) => sectionLink.teardown());
+    this.topicTrackingState.offStateChange(this.callbackId);
+  }
+
+  // Override in child
+  get defaultMainSectionLinks() {
+    return [];
+  }
+
+  // Override in child
+  get defaultAdminMainSectionLinks() {
+    return [];
+  }
+
+  // Override in child
+  get defaultMoreSectionLinks() {
+    return [];
+  }
+
+  // Override in child
+  get defaultMoreSecondarySectionLinks() {
+    return [];
   }
 
   #initializeSectionLink(sectionLinkClass) {

app/assets/javascripts/discourse/app/components/sidebar/user/community-section.js

@@ -21,22 +21,6 @@ export default class SidebarUserCommunitySection extends SidebarCommonCommunityS
   constructor() {
     super(...arguments);
 
-    this.defaultMoreSectionLinks = [
-      GroupsSectionLink,
-      UsersSectionLink,
-      BadgesSectionLink,
-    ];
-
-    this.defaultMoreSecondarySectionLinks = [AboutSectionLink, FAQSectionLink];
-
-    this.defaultMainSectionLinks = [
-      EverythingSectionLink,
-      TrackedSectionLink,
-      MyPostsSectionLink,
-    ];
-
-    this.defaultAdminMainSectionLinks = [AdminSectionLink];
-
     this.headerActionsIcon = "plus";
 
     this.headerActions = [
@@ -47,6 +31,22 @@ export default class SidebarUserCommunitySection extends SidebarCommonCommunityS
     ];
   }
 
+  get defaultMainSectionLinks() {
+    return [EverythingSectionLink, TrackedSectionLink, MyPostsSectionLink];
+  }
+
+  get defaultAdminMainSectionLinks() {
+    return [AdminSectionLink];
+  }
+
+  get defaultMoreSectionLinks() {
+    return [GroupsSectionLink, UsersSectionLink, BadgesSectionLink];
+  }
+
+  get defaultMoreSecondarySectionLinks() {
+    return [AboutSectionLink, FAQSectionLink];
+  }
+
   @action
   composeTopic() {
     const composerArgs = {

app/assets/javascripts/discourse/app/lib/sidebar/base-community-section-link.js

@@ -16,6 +16,11 @@ export default class BaseCommunitySectionLink {
     this.siteSettings = siteSettings;
   }
 
+  /**
+   * Called when state has changed in the TopicTrackingState service
+   */
+  onTopicTrackingStateChange() {}
+
   /**
    * Called when community-section component is torn down.
    */

app/assets/javascripts/discourse/app/lib/sidebar/common/community-section/everything-section-link.js

@@ -1,34 +1,26 @@
 import I18n from "I18n";
 
 import { tracked } from "@glimmer/tracking";
-import { bind } from "discourse-common/utils/decorators";
 import BaseSectionLink from "discourse/lib/sidebar/base-community-section-link";
 
 export default class EverythingSectionLink extends BaseSectionLink {
   @tracked totalUnread = 0;
   @tracked totalNew = 0;
-  callbackId = null;
 
   constructor() {
     super(...arguments);
-
-    if (this.currentUser) {
-      this.callbackId = this.topicTrackingState.onStateChange(
-        this._refreshCounts
-      );
-
-      this._refreshCounts();
-    }
+    this.#refreshCounts();
   }
 
-  teardown() {
-    if (this.callbackId) {
-      this.topicTrackingState.offStateChange(this.callbackId);
-    }
+  onTopicTrackingStateChange() {
+    this.#refreshCounts();
+  }
+
+  #refreshCounts() {
+    if (!this.currentUser) {
+      return;
     }
 
-  @bind
-  _refreshCounts() {
     this.totalUnread = this.topicTrackingState.countUnread();
 
     if (this.totalUnread === 0) {

app/assets/javascripts/discourse/app/lib/sidebar/user/community-section/tracked-section-link.js

@@ -1,30 +1,23 @@
 import I18n from "I18n";
 
 import { tracked } from "@glimmer/tracking";
-import { bind } from "discourse-common/utils/decorators";
 import BaseSectionLink from "discourse/lib/sidebar/base-community-section-link";
 import { isTrackedTopic } from "discourse/lib/topic-list-tracked-filter";
 
 export default class TrackedSectionLink extends BaseSectionLink {
   @tracked totalUnread = 0;
   @tracked totalNew = 0;
-  callbackId = null;
 
   constructor() {
     super(...arguments);
-
-    this.callbackId = this.topicTrackingState.onStateChange(
-      this._refreshCounts
-    );
-    this._refreshCounts();
+    this.#refreshCounts();
   }
 
-  teardown() {
-    this.topicTrackingState.offStateChange(this.callbackId);
+  onTopicTrackingStateChange() {
+    this.#refreshCounts();
   }
 
-  @bind
-  _refreshCounts() {
+  #refreshCounts() {
     this.totalUnread = this.topicTrackingState.countUnread({
       customFilterFn: isTrackedTopic,
     });