fix(components/tabs): show vertical tab content when activated programmatically after init

libs/components/tabs/src/lib/modules/vertical-tabset/fixtures/vertical-tabs-fixtures.module.ts

@@ -9,6 +9,7 @@ import { VerticalTabsetEmptyGroupTestComponent } from './vertical-tabset-empty-g
 import { VerticalTabsetWithNgForTestComponent } from './vertical-tabset-ngfor.component.fixture';
 import { VerticalTabsetNoActiveTestComponent } from './vertical-tabset-no-active.component.fixture';
 import { VerticalTabsetNoGroupTestComponent } from './vertical-tabset-no-group.component.fixture';
+import { VerticalTabsetProgrammaticTestComponent } from './vertical-tabset-programmatic.component';
 import { VerticalTabsetTestComponent } from './vertical-tabset.component.fixture';
 
 @NgModule({
@@ -24,12 +25,14 @@ import { VerticalTabsetTestComponent } from './vertical-tabset.component.fixture
     FormsModule,
     NoopAnimationsModule,
     SkyVerticalTabsetModule,
+    VerticalTabsetProgrammaticTestComponent,
   ],
   exports: [
     VerticalTabsetTestComponent,
     VerticalTabsetEmptyGroupTestComponent,
     VerticalTabsetNoGroupTestComponent,
     VerticalTabsetNoActiveTestComponent,
+    VerticalTabsetProgrammaticTestComponent,
     VerticalTabsetWithNgForTestComponent,
   ],
 })

libs/components/tabs/src/lib/modules/vertical-tabset/fixtures/vertical-tabset-programmatic.component.ts

@@ -0,0 +1,22 @@
+import { Component } from '@angular/core';
+
+import { SkyVerticalTabsetModule } from '../vertical-tabset.module';
+
+@Component({
+  standalone: true,
+  template: `<sky-vertical-tabset>
+    <sky-vertical-tab tabHeading="Tab 1" [active]="activeIndex === 0">
+      Tab 1 content
+    </sky-vertical-tab>
+    <sky-vertical-tab tabHeading="Tab 2" [active]="activeIndex === 1">
+      Tab 2 content
+    </sky-vertical-tab>
+    <sky-vertical-tab tabHeading="Tab 3" [active]="activeIndex === 2">
+      Tab 3 content
+    </sky-vertical-tab>
+  </sky-vertical-tabset>`,
+  imports: [SkyVerticalTabsetModule],
+})
+export class VerticalTabsetProgrammaticTestComponent {
+  public activeIndex = 0;
+}

libs/components/tabs/src/lib/modules/vertical-tabset/fixtures/vertical-tabset.component.fixture.ts

@@ -9,7 +9,7 @@ import { SkyVerticalTabsetComponent } from '../vertical-tabset.component';
   styleUrls: ['./vertical-tabset.component.fixture.scss'],
 })
 export class VerticalTabsetTestComponent {
-  public active = true;
+  public active: boolean | undefined = true;
 
   public group1Open = true;
   public group1Disabled = false;

libs/components/tabs/src/lib/modules/vertical-tabset/vertical-tab.component.ts

@@ -41,9 +41,21 @@ let nextId = 0;
 export class SkyVerticalTabComponent implements OnInit, OnDestroy {
   /**
    * Whether the tab is active when the tabset loads.
+   * @default false
    */
   @Input()
-  public active: boolean | undefined = false;
+  public set active(value: boolean | undefined) {
+    if (value !== this.#_active) {
+      this.#_active = value ?? false;
+      this.#tabsetService.activateTab(this);
+    }
+  }
+
+  public get active(): boolean {
+    return this.#_active;
+  }
+
+  #_active = false;
 
   /**
    * The HTML element ID of the element that contains

libs/components/tabs/src/lib/modules/vertical-tabset/vertical-tabset.component.spec.ts

@@ -14,6 +14,7 @@ import { VerticalTabsetEmptyGroupTestComponent } from './fixtures/vertical-tabse
 import { VerticalTabsetWithNgForTestComponent } from './fixtures/vertical-tabset-ngfor.component.fixture';
 import { VerticalTabsetNoActiveTestComponent } from './fixtures/vertical-tabset-no-active.component.fixture';
 import { VerticalTabsetNoGroupTestComponent } from './fixtures/vertical-tabset-no-group.component.fixture';
+import { VerticalTabsetProgrammaticTestComponent } from './fixtures/vertical-tabset-programmatic.component';
 import { VerticalTabsetTestComponent } from './fixtures/vertical-tabset.component.fixture';
 import { SkyVerticalTabMediaQueryService } from './vertical-tab-media-query.service';
 import { SkyVerticalTabsetComponent } from './vertical-tabset.component';
@@ -26,7 +27,7 @@ function getVisibleTabContentPane(
 ): HTMLElement[] {
   return Array.from(
     fixture.nativeElement.querySelectorAll(
-      '.sky-vertical-tab-content-pane:not(.sky-vertical-tab-hidden)',
+      '.sky-vertical-tabset-content .sky-vertical-tab-content-pane:not(.sky-vertical-tab-hidden)',
     ),
   );
 }
@@ -453,6 +454,37 @@ describe('Vertical tabset component', () => {
     expect(elementHasFocus(tabButtons[0])).toBeTrue();
   });
 
+  it('should set a tab active=false when set to undefined', () => {
+    const fixture = createTestComponent();
+
+    fixture.componentInstance.active = undefined;
+    fixture.detectChanges();
+
+    const tabButtons = getAllTabButtons(fixture);
+    expect(elementHasFocus(tabButtons[0])).toBeFalse();
+
+    const visibleTabs = getVisibleTabContentPane(fixture);
+    expect(visibleTabs.length).toBe(0);
+  });
+
+  it('should programmatically select tabs', () => {
+    const fixture = TestBed.createComponent(
+      VerticalTabsetProgrammaticTestComponent,
+    );
+
+    // Activate first tab.
+    fixture.componentInstance.activeIndex = 0;
+    fixture.detectChanges();
+
+    // Activate second tab.
+    fixture.componentInstance.activeIndex = 1;
+    fixture.detectChanges();
+
+    const visibleTabs = getVisibleTabContentPane(fixture);
+    expect(visibleTabs.length).toBe(1);
+    expect(visibleTabs[0]).toHaveText('Tab 2 content');
+  });
+
   it("should focus the active tab's group when the tabs container is focused and the tab's group is collapsed", fakeAsync(() => {
     mockQueryService.fire(SkyMediaBreakpoints.lg);
     const fixture = createTestComponent();