fix(docs-infra): highlight the currently active node in top-bar (#33351)

Related to #33239 and #33255.

PR Close #33351

aio/src/app/app.component.html

@@ -22,7 +22,7 @@
       <img *ngSwitchCase="true" src="assets/images/logos/angular/logo-nav@2x.png" width="150" height="40" title="Home" alt="Home">
       <img *ngSwitchDefault src="assets/images/logos/angular/shield-large.svg" width="37" height="40" title="Home" alt="Home">
     </a>
-    <aio-top-menu *ngIf="isSideBySide" [nodes]="topMenuNodes"></aio-top-menu>
+    <aio-top-menu *ngIf="isSideBySide" [nodes]="topMenuNodes" [currentNode]="currentNodes?.TopBar"></aio-top-menu>
     <aio-search-box class="search-container" #searchBox (onSearch)="doSearch($event)" (onFocus)="doSearch($event)"></aio-search-box>
     <div class="toolbar-external-icons-container">
       <a href="https://twitter.com/angular" title="Twitter" aria-label="Angular on twitter">

aio/src/app/layout/top-menu/top-menu.component.spec.ts

@@ -10,6 +10,8 @@ describe('TopMenuComponent', () => {
     const list: HTMLUListElement = fixture.debugElement.nativeElement.querySelector('ul');
     return Array.from(list.querySelectorAll('li'));
   };
+  const getSelected = (items: HTMLLIElement[]) =>
+    items.filter(item => item.classList.contains('selected'));
 
   beforeEach(() => {
     TestBed.configureTestingModule({
@@ -38,4 +40,47 @@ describe('TopMenuComponent', () => {
     expect(links.map(link => link.textContent)).toEqual(['API', 'Features']);
     expect(links.map(link => link.title)).toEqual(['API docs', 'Angular features overview']);
   });
+
+  it('should mark the currently selected node with `.selected`', () => {
+    const items = getListItems();
+    expect(getSelected(items)).toEqual([]);
+
+    component.currentNode = {url: 'api', view: 'foo', nodes: []};
+    fixture.detectChanges();
+    expect(getSelected(items)).toEqual([items[0]]);
+
+    component.currentNode = {url: 'features', view: 'foo', nodes: []};
+    fixture.detectChanges();
+    expect(getSelected(items)).toEqual([items[1]]);
+
+    component.currentNode = {url: 'something/else', view: 'foo', nodes: []};
+    fixture.detectChanges();
+    expect(getSelected(items)).toEqual([]);
+  });
+
+  it('should not mark any node with `.selected` if the current URL is undefined', () => {
+    component.nodes = [
+      {url: '', title: 'API', tooltip: 'API docs'},
+      {url: undefined, title: 'Features', tooltip: 'Angular features overview'},
+    ];
+    fixture.detectChanges();
+    const items = getListItems();
+
+    component.currentNode = undefined;
+    fixture.detectChanges();
+    expect(getSelected(items)).toEqual([]);
+  });
+
+  it('should correctly mark a node with `.selected` even if its URL is empty', () => {
+    component.nodes = [
+      {url: '', title: 'API', tooltip: 'API docs'},
+      {url: undefined, title: 'Features', tooltip: 'Angular features overview'},
+    ];
+    fixture.detectChanges();
+    const items = getListItems();
+
+    component.currentNode = {url: '', view: 'Empty url', nodes: []};
+    fixture.detectChanges();
+    expect(getSelected(items)).toEqual([items[0]]);
+  });
 });

aio/src/app/layout/top-menu/top-menu.component.ts

@@ -1,11 +1,11 @@
 import { Component, Input } from '@angular/core';
-import { NavigationNode } from 'app/navigation/navigation.service';
+import { CurrentNode, NavigationNode } from 'app/navigation/navigation.service';
 
 @Component({
   selector: 'aio-top-menu',
   template: `
     <ul role="navigation">
-      <li *ngFor="let node of nodes">
+      <li *ngFor="let node of nodes" [ngClass]="{selected: node.url === currentUrl}">
         <a class="nav-link" [href]="node.url" [title]="node.tooltip">
           <span class="nav-link-inner">{{ node.title }}</span>
         </a>
@@ -14,5 +14,7 @@ import { NavigationNode } from 'app/navigation/navigation.service';
 })
 export class TopMenuComponent {
   @Input() nodes: NavigationNode[];
+  @Input() currentNode: CurrentNode | undefined;
 
+  get currentUrl(): string | null { return this.currentNode ? this.currentNode.url : null; }
 }

aio/src/styles/1-layouts/_top-menu.scss

@@ -149,7 +149,6 @@ aio-top-menu {
       &:focus {
         outline: none;
       }
-    }
 
       a.nav-link {
         margin: 0 4px;
@@ -157,11 +156,11 @@ aio-top-menu {
         cursor: pointer;
 
         .nav-link-inner {
+          border-radius: 4px;
           padding: 8px 16px;
 
           &:hover {
             background: rgba($white, 0.15);
-          border-radius: 4px;
           }
         }
 
@@ -178,12 +177,19 @@ aio-top-menu {
         &:active {
           .nav-link-inner {
             background: rgba($white, 0.15);
-          border-radius: 4px;
-        }
           }
         }
       }
 
+      &.selected {
+        a.nav-link {
+          .nav-link-inner {
+            background: rgba($white, 0.15);
+          }
+        }
+      }
+    }
+  }
 }
 
 // SEARCH BOX