fix: navbar active link should match the most specific path

packages/ui-components/src/Common/BaseActiveLink/__tests__/index.test.jsx

@@ -49,4 +49,42 @@ describe('ActiveLink', () => {
       'link active'
     );
   });
+
+  it('forces active class when active override is true regardless of pathname', async () => {
+    render(
+      <ActiveLink
+        className="link"
+        activeClassName="active"
+        href="/link"
+        pathname="/not-link"
+        active
+      >
+        Link
+      </ActiveLink>
+    );
+
+    assert.equal(
+      (await screen.findByText('Link')).getAttribute('class'),
+      'link active'
+    );
+  });
+
+  it('forces inactive when active override is false even when pathname matches', async () => {
+    render(
+      <ActiveLink
+        className="link"
+        activeClassName="active"
+        href="/link"
+        pathname="/link"
+        active={false}
+      >
+        Link
+      </ActiveLink>
+    );
+
+    assert.equal(
+      (await screen.findByText('Link')).getAttribute('class'),
+      'link'
+    );
+  });
 });

packages/ui-components/src/Common/BaseActiveLink/index.tsx

@@ -7,6 +7,7 @@ export type ActiveLocalizedLinkProps = ComponentProps<LinkLike> & {
   activeClassName?: string;
   allowSubPath?: boolean;
   pathname?: string;
+  active?: boolean;
   as?: LinkLike;
 };
 
@@ -16,17 +17,21 @@ const BaseActiveLink: FC<ActiveLocalizedLinkProps> = ({
   className,
   href = '',
   pathname = '/',
+  active,
   as: Component = 'a',
   ...props
 }) => {
-  const finalClassName = classNames(className, {
-    [activeClassName]: allowSubPath
+  // NavBar sets `active` explicitly; if it's not passed we fall back to the path check.
+  const isActive =
+    active ??
+    (allowSubPath
       ? // When using allowSubPath we want only to check if
         // the current pathname starts with the utmost upper level
         // of an href (e.g. /docs/...)
         pathname.startsWith(`/${href.toString().split('/')[1]}`)
-      : href.toString() === pathname,
-  });
+      : href.toString() === pathname);
+
+  const finalClassName = classNames(className, { [activeClassName]: isActive });
 
   return <Component className={finalClassName} href={href} {...props} />;
 };

packages/ui-components/src/Containers/NavBar/NavItem/index.tsx

@@ -17,6 +17,7 @@ type NavItemProps = {
   target?: HTMLAttributeAnchorTarget | undefined;
 
   pathname: string;
+  active?: boolean;
   as: LinkLike;
 };
 

packages/ui-components/src/Containers/NavBar/__tests__/index.test.jsx

@@ -0,0 +1,43 @@
+import { describe, it } from 'node:test';
+import assert from 'node:assert/strict';
+
+import { getActiveNavLink } from '..';
+
+const navItems = [
+  { link: '/about' },
+  { link: '/about/sponsors' },
+  { link: '/docs' },
+  { link: 'https://nodejs.org/learn' },
+];
+
+describe('getActiveNavLink', () => {
+  it('picks the most specific sibling on its own pages', () => {
+    assert.equal(
+      getActiveNavLink(navItems, '/about/sponsors'),
+      '/about/sponsors'
+    );
+  });
+
+  it('keeps the parent active on its other sub-pages', () => {
+    assert.equal(
+      getActiveNavLink(navItems, '/about/governance/charter'),
+      '/about'
+    );
+  });
+
+  it('matches the parent on its own index page', () => {
+    assert.equal(getActiveNavLink(navItems, '/about'), '/about');
+  });
+
+  it('does not match across word boundaries', () => {
+    assert.equal(getActiveNavLink(navItems, '/about-us'), '');
+  });
+
+  it('never returns an external (non-internal) link', () => {
+    assert.equal(getActiveNavLink(navItems, 'https://nodejs.org/learn'), '');
+  });
+
+  it('returns empty string when nothing matches', () => {
+    assert.equal(getActiveNavLink(navItems, '/unknown'), '');
+  });
+});

packages/ui-components/src/Containers/NavBar/index.tsx

@@ -21,6 +21,18 @@ const navInteractionIcons = {
   close: <XMark className={styles.navInteractionIcon} />,
 };
 
+// Picks the longest nav link that prefixes the current path, so `/about` and `/about/sponsors` never highlight together.
+export const getActiveNavLink = (
+  navItems: Array<{ link: string }>,
+  pathname: string
+): string =>
+  navItems.reduce((longest, { link }) => {
+    const isMatch =
+      link.startsWith('/') &&
+      (pathname === link || pathname.startsWith(`${link}/`));
+    return isMatch && link.length > longest.length ? link : longest;
+  }, '');
+
 type NavbarProps = {
   navItems?: Array<{
     text: FormattedMessage;
@@ -43,6 +55,8 @@ const NavBar: FC<PropsWithChildren<NavbarProps>> = ({
 }) => {
   const [isMenuOpen, setIsMenuOpen] = useState(false);
 
+  const activeLink = getActiveNavLink(navItems ?? [], pathname);
+
   return (
     <nav className={styles.container}>
       <div className={styles.innerContainer}>
@@ -79,6 +93,7 @@ const NavBar: FC<PropsWithChildren<NavbarProps>> = ({
               {navItems.map(({ text, link, target }) => (
                 <NavItem
                   pathname={pathname}
+                  active={link === activeLink}
                   as={Component}
                   key={link}
                   href={link}