build(aio): fix warning about missing `<h1>`

Fixes #17549

aio/content/marketing/index.html

@@ -1,10 +1,10 @@
-<!--FULL HEADER BLOCK-->
+<!-- FULL HEADER BLOCK -->
 <header>
 
-  <!--BACKGROUND IMAGE-->
+  <!-- BACKGROUND IMAGE -->
   <div class="background-sky hero"></div>
 
-<!--INTRO SECTION -->
+  <!-- INTRO SECTION -->
   <section id="intro">
 
     <!-- LOGO -->
@@ -12,31 +12,33 @@
       <img src="assets/images/logos/angular/angular.svg"/>
     </div>
 
-      <!-- CONTAINER     -->
+    <!-- CONTAINER -->
     <div class="homepage-container">
-      <!-- container content starts -->
-
       <div class="hero-headline no-toc">One framework.<br>Mobile &amp; desktop.</div>
       <a class="button hero-cta" href="guide/quickstart">Get Started</a>
-  </div><!-- CONTAINER END -->
-  </section>
+    </div>
 
+  </section>
 
 </header>
 
+<!-- MAIN CONTENT -->
 <article>
+
+  <h1 class="no-toc" style="display: none"></h1>
+
   <div class="home-rows">
 
-    <!--Announcement Bar-->
+    <!-- Announcement Bar -->
     <div class="homepage-container">
       <div class="announcement-bar">
         <img src="generated/images/marketing/home/angular-mix.png" height="40" width="151">
         <p>Join us at our newest event, October 2017</p>
         <a class="button" href="https://angularmix.com/">Learn More</a>
-     </div>
+      </div>
     </div>
 
-    <!-- Group 1-->
+    <!-- Group 1 -->
     <div layout="row" layout-xs="column" class="home-row homepage-container">
       <div class="promo-img-container promo-1">
         <div>
@@ -53,7 +55,8 @@
       </div>
     </div>
     <hr>
-    <!-- Group 2-->
+
+    <!-- Group 2 -->
     <div layout="row" layout-xs="column" class="home-row">
       <div class="text-container">
         <div class="text-block">
@@ -71,7 +74,7 @@
     </div>
     <hr>
 
-    <!-- Group 3-->
+    <!-- Group 3 -->
     <div layout="row" layout-xs="column" class="home-row">
       <div class="promo-img-container promo-3">
         <div><img src="generated/images/marketing/home/joyful-development.svg" alt="IDE example"></div>
@@ -88,9 +91,8 @@
     </div>
     <hr>
 
-    <!-- Group 4-->
+    <!-- Group 4 -->
     <div layout="row" layout-xs="column" class="home-row">
-
       <div class="text-container">
         <div class="text-block l-pad-top-2">
           <div class="text-headline">Loved by Millions</div>
@@ -105,20 +107,19 @@
       </div>
     </div>
 
-  <!-- CTA CARDS -->
-  <div layout="row" layout-xs="column" class="home-row">
-
-    <a href="guide/quickstart">
-      <div class="card">
+    <!-- CTA CARDS -->
+    <div layout="row" layout-xs="column" class="home-row">
+      <a href="guide/quickstart">
+        <div class="card">
           <img src="generated/images/marketing/home/code-icon.svg" height="70px">
           <div class="card-text-container">
             <div class="text-headline">Get Started</div>
             <p>Start building your Angular application.</p>
           </div>
-      </div>
-    </a>
-  </div>
+        </div>
+      </a>
+    </div>
 
-  </div> <!-- end of home rows -->
+  </div><!-- end of home rows -->
 
 </article>

aio/tools/transforms/angular-base-package/post-processors/h1-checker.js

@@ -34,5 +34,5 @@ function getText(h1) {
     (node.properties.ariaHidden === 'true' || node.properties['aria-hidden'] === 'true')
   ));
 
-  return toString(cleaned);
-}
+  return cleaned ? toString(cleaned) : '';
+}

aio/tools/transforms/angular-base-package/post-processors/h1-checker.spec.js

@@ -69,4 +69,14 @@ describe('h1Checker postprocessor', () => {
     processor.$process([doc]);
     expect(doc.vFile.title).toEqual('What is Angular?');
   });
-});
+
+  it('should not break if the h1 is empty (except for an aria-hidden anchor)', () => {
+    const doc = {
+      docType: 'a',
+      renderedContent: `
+        <h1><a aria-hidden="true"></a></h1>
+      `
+    };
+    expect(() => processor.$process([doc])).not.toThrow();
+  });
+});