Dedupe head sitemap link tags (#3457)

Co-authored-by: Chris Swithinbank <swithinbank@gmail.com>
Co-authored-by: Felix Schneider <99918022+trueberryless@users.noreply.github.com>

Author: 3 people

.changeset/mean-icons-sneeze.md

@@ -0,0 +1,9 @@
+---
+'@astrojs/starlight': patch
+---
+
+Deduplicates sitemap link tags in the head.
+
+When [enabling sitemap](https://starlight.astro.build/guides/customization/#enable-sitemap) in Starlight, a `<link rel="sitemap" href="/sitemap-index.xml">` tag is automatically added to the head of each page. Manually specifying sitemap link tags using the Starlight [`head` configuration option](https://starlight.astro.build/reference/configuration/#head) or the [`head` frontmatter field](https://starlight.astro.build/reference/frontmatter/#head) will now override the default sitemap link tag added by Starlight.
+
+This change ensures that users manually adding the `@astrojs/sitemap` integration to the Astro `integrations` array for more fine-grained control over sitemap generation and also using the [`filenameBase` integration option](https://docs.astro.build/en/guides/integrations-guide/sitemap/#filenamebase) can customize the sitemap link tag in the head.

packages/starlight/__tests__/head/head.test.ts

@@ -84,6 +84,17 @@ test('merges two <link rel="canonical" href="" /> tags', () => {
 	]);
 });
 
+test('merges two <link rel="sitemap" href="" /> tags', () => {
+	const customLink = {
+		tag: 'link',
+		attrs: { rel: 'sitemap', href: '/sitemap-custom.xml' },
+	} as const;
+	const head = getTestHead([customLink]);
+	expect(head.filter((tag) => tag.tag === 'link' && tag.attrs?.rel === 'sitemap')).toEqual([
+		customLink,
+	]);
+});
+
 test('does not merge same link tags', () => {
 	const customLink = {
 		tag: 'link',

packages/starlight/utils/head.ts

@@ -120,7 +120,8 @@ function createHead(defaults: HeadUserConfig, ...heads: HeadConfig[]) {
 }
 
 /**
- * Test if a head config object contains a matching `<title>` or `<meta>` or `<link rel="canonical">` tag.
+ * Test if a head config object contains a matching `<title>`, `<meta>`, `<link rel="canonical">`
+ * or `<link rel="sitemap">` tag.
  *
  * For example, will return true if `head` already contains
  * `<meta name="description" content="A">` and the passed `tag`
@@ -135,7 +136,9 @@ function hasTag(head: HeadConfig, entry: HeadConfig[number]): boolean {
 			return hasOneOf(head, entry, ['name', 'property', 'http-equiv']);
 		case 'link':
 			return head.some(
-				({ attrs }) => entry.attrs?.rel === 'canonical' && attrs?.rel === 'canonical'
+				({ attrs }) =>
+					(entry.attrs?.rel === 'canonical' && attrs?.rel === 'canonical') ||
+					(entry.attrs?.rel === 'sitemap' && attrs?.rel === 'sitemap')
 			);
 		default:
 			return false;