when clicking on toc entry, focus on respective heading in content (#7845)

Co-authored-by: katiegoines <[email protected]>

Author: katieklein

src/components/MDXComponents/MDXHeading.tsx

@@ -5,7 +5,7 @@ export const MDXHeading = (props) => {
   const { level, children, id } = props;
 
   return (
-    <Heading level={level} id={id}>
+    <Heading level={level} id={id} tabIndex={-1}>
       {/* Only output heading links for h2 and h3 \ */}
       {level == 2 || level == 3 ? (
         <Link href={`#${id}`}>{children}</Link>

src/components/MDXComponents/__tests__/MDXHeading.test.tsx

@@ -1,5 +1,7 @@
 import { render, screen } from '@testing-library/react';
 import { MDXHeading } from '../MDXHeading';
+import { TableOfContents } from '../../TableOfContents/index';
+import userEvent from '@testing-library/user-event';
 
 describe('MDXHeading', () => {
   it('should render H2 with string and anchor link', () => {
@@ -53,4 +55,28 @@ describe('MDXHeading', () => {
     expect(heading).toHaveTextContent(props.children);
     expect(link).not.toBeInTheDocument();
   });
+
+  it('should shift focus to in-content heading on TOC click', async () => {
+    const props = {
+      level: 2,
+      children: 'Test heading',
+      id: 'test-heading'
+    };
+    render(<MDXHeading {...props} />);
+
+    const heading = screen.queryByRole('heading', { level: 2 });
+    const tocHeadings = [
+      { linkText: 'Test heading', hash: 'test-heading', level: 'h2' }
+    ];
+
+    const tableOfContents = <TableOfContents headers={tocHeadings} />;
+    render(tableOfContents);
+
+    const tocEntry = await screen.findByRole('heading', {
+      name: 'Test heading'
+    });
+
+    userEvent.click(tocEntry);
+    expect(heading).toHaveFocus();
+  });
 });

src/styles/base.scss

@@ -187,6 +187,12 @@ ol:not([class]) {
   .amplify-heading--2,
   .amplify-heading--3 {
     scroll-margin-top: 9rem;
+
+    &:focus-visible {
+      transition: none;
+      outline: 2px solid var(--amplify-colors-border-focus);
+      outline-offset: 2px;
+    }
   }
 }