FIX: Admin sidebar was hiding chat/forum toggle button (#25781)

We have separated and combined modes for sidebar panels.
Separated means the panels show only their own sections,
combined means sections from all panels are shown.

The admin sidebar only shows its own panels, so it must set
the mode to separated; however when we navigate to chat or
home we must revert to the initial mode setttings.

app/assets/javascripts/admin/addon/routes/admin.js

@@ -1,5 +1,11 @@
+import { tracked } from "@glimmer/tracking";
 import { inject as service } from "@ember/service";
-import { ADMIN_PANEL, MAIN_PANEL } from "discourse/lib/sidebar/panels";
+import {
+  ADMIN_PANEL,
+  COMBINED_MODE,
+  MAIN_PANEL,
+  SEPARATED_MODE,
+} from "discourse/lib/sidebar/panels";
 import DiscourseRoute from "discourse/routes/discourse";
 import I18n from "discourse-i18n";
 
@@ -7,6 +13,7 @@ export default class AdminRoute extends DiscourseRoute {
   @service sidebarState;
   @service siteSettings;
   @service currentUser;
+  @tracked initialSidebarState;
 
   titleToken() {
     return I18n.t("admin_title");
@@ -14,6 +21,11 @@ export default class AdminRoute extends DiscourseRoute {
 
   activate() {
     if (this.currentUser.use_admin_sidebar) {
+      this.initialSidebarState = {
+        mode: this.sidebarState.mode,
+        displaySwitchPanelButtons: this.sidebarState.displaySwitchPanelButtons,
+      };
+
       this.sidebarState.setPanel(ADMIN_PANEL);
       this.sidebarState.setSeparatedMode();
       this.sidebarState.hideSwitchPanelButtons();
@@ -29,6 +41,18 @@ export default class AdminRoute extends DiscourseRoute {
 
     if (this.currentUser.use_admin_sidebar) {
       if (!transition?.to.name.startsWith("admin")) {
+        if (this.initialSidebarState.mode === SEPARATED_MODE) {
+          this.sidebarState.setSeparatedMode();
+        } else if (this.initialSidebarState.mode === COMBINED_MODE) {
+          this.sidebarState.setCombinedMode();
+        }
+
+        if (this.initialSidebarState.displaySwitchPanelButtons) {
+          this.sidebarState.showSwitchPanelButtons();
+        } else {
+          this.sidebarState.hideSwitchPanelButtons();
+        }
+
         this.sidebarState.setPanel(MAIN_PANEL);
       }
     }

plugins/chat/assets/javascripts/discourse/lib/init-sidebar-state.js

@@ -4,12 +4,6 @@ import { getUserChatSeparateSidebarMode } from "discourse/plugins/chat/discourse
 export const CHAT_PANEL = "chat";
 
 export function initSidebarState(api, user) {
-  if (api.getSidebarPanel()?.key === ADMIN_PANEL) {
-    return;
-  }
-
-  api.setSidebarPanel(MAIN_PANEL);
-
   const chatSeparateSidebarMode = getUserChatSeparateSidebarMode(user);
   if (chatSeparateSidebarMode.fullscreen) {
     api.setCombinedSidebarMode();
@@ -20,4 +14,10 @@ export function initSidebarState(api, user) {
     api.setCombinedSidebarMode();
     api.hideSidebarSwitchPanelButtons();
   }
+
+  if (api.getSidebarPanel()?.key === ADMIN_PANEL) {
+    return;
+  }
+
+  api.setSidebarPanel(MAIN_PANEL);
 }

plugins/chat/spec/system/admin_sidebar_navigation_spec.rb

@@ -22,4 +22,31 @@ describe "Admin Revamp | Sidebar Navigation | Plugin Links", type: :system do
     find(".header-sidebar-toggle").click
     expect(sidebar).to have_section_link("Chat", href: "/admin/plugins/chat", count: 1)
   end
+
+  describe "admin sidebar respects separated and combined sidebar modes" do
+    it "reverts to always (separated) mode after entering and leaving admin section" do
+      admin.user_option.update!(
+        chat_separate_sidebar_mode: UserOption.chat_separate_sidebar_modes[:always],
+      )
+      visit("/")
+      expect(sidebar).to have_switch_button("chat")
+      sidebar.click_link_in_section("community", "admin")
+      expect(sidebar).to have_no_switch_button("chat")
+      find("#site-logo").click
+      expect(sidebar).to have_switch_button("chat")
+    end
+
+    it "reverts to the never (combined) mode after entering and leaving admin section" do
+      admin.user_option.update!(
+        chat_separate_sidebar_mode: UserOption.chat_separate_sidebar_modes[:never],
+      )
+      visit("/")
+      expect(sidebar).to have_section("chat-channels")
+      expect(sidebar).to have_no_switch_button("chat")
+      sidebar.click_link_in_section("community", "admin")
+      expect(sidebar).to have_no_section("chat-channels")
+      find("#site-logo").click
+      expect(sidebar).to have_section("chat-channels")
+    end
+  end
 end