Added support for single localization

dist/modules/seo/hreflang.js

@@ -1,37 +1,36 @@
-import { buildLocalizedPath, getDefaultLocale, getLocaleCodes } from '../i18n/index.js';
+import { buildLocalizedPath, getLocaleCodes } from '../i18n/index.js';
 /**
+ * Builds a map of locale → URL for hreflang alternate links, suitable for
  * Next.js Metadata `alternates.languages`.
  *
  * Bridges SEO and i18n: for each configured locale that the document has a
  * slug in, it produces the locale-aware path (via buildLocalizedPath),
  * optionally prefixed with an absolute origin.
  *
- * Also emits `x-default` pointing at the default locale — the version Google
- * serves when the user's language/region matches no hreflang, and the fallback
- * when the root ('/') redirect is ambiguous (Googlebot with no/foreign
- * Accept-Language).
- *
  * @example
  * buildHreflangAlternates({
  *   slugs: { pl: 'o-nas', en: 'about' },
  *   config,
  *   baseUrl: 'https://example.com',
  * })
- * // → {
- * //   pl: 'https://example.com/pl/o-nas',
- * //   en: 'https://example.com/en/about',
- * //   'x-default': 'https://example.com/pl/o-nas',
- * // }
- */ export function buildHreflangAlternates({ baseUrl, config, homeSlug = 'home', prefix, slugs }) {
+ * // → { pl: 'https://example.com/pl/o-nas', en: 'https://example.com/en/about' }
+ */ export function buildHreflangAlternates({ slugs, config, baseUrl, homeSlug = 'home', prefix }) {
     const origin = baseUrl?.replace(/\/$/, '') ?? '';
     const alternates = {};
+    // Single-locale sites have no language alternatives — hreflang describes
+    // relationships BETWEEN language versions, and there's only one. Emitting
+    // hreflang (or x-default) here would be wrong, so return empty: the page keeps
+    // its canonical, but no alternate-language links.
+    if (config.locales.length === 1) {
+        return alternates;
+    }
     for (const locale of getLocaleCodes(config)){
         const path = buildLocalizedPath({
+            slugs,
+            locale,
             config,
             homeSlug,
-            locale,
-            prefix,
-            slugs
+            prefix
         });
         if (path) {
             alternates[locale] = `${origin}${path}`;
@@ -42,7 +41,7 @@ import { buildLocalizedPath, getDefaultLocale, getLocaleCodes } from '../i18n/in
     // redirect is ambiguous (Googlebot with no/foreign Accept-Language). Point it
     // at the default locale (the primary market) so search shows that version by
     // default instead of guessing. Only set when the default locale has a URL.
-    const defaultLocalePath = alternates[getDefaultLocale(config)];
+    const defaultLocalePath = alternates[config.defaultLocale];
     if (defaultLocalePath) {
         alternates['x-default'] = defaultLocalePath;
     }