fix(i18n): handle double-prefixed legacy English routes

Generate additional static paths under /en/ for slugs that already
contain the en-US/ prefix (e.g. /en/en-US/product-overview/) so
they redirect to the canonical /en-US/ path. Add a toCanonicalEnglishPath
helper to normalize redirect targets and extend i18n and
langParamHandler test suites with double-prefix coverage.

Co-Authored-By: Hagicode <noreply@hagicode.com>
Signed-off-by: newbe36524 <newbe36524@qq.com>

Author: newbe36524

src/lib/i18n.test.ts

@@ -115,6 +115,7 @@ describe('docs locale helpers', () => {
 
   it.each([
     ['/en-US/product-overview/', '/en-US/product-overview/'],
+    ['/en/en-US/product-overview/', '/en-US/product-overview/'],
     ['/en-US/ja-JP/product-overview/', '/ja-JP/product-overview/'],
     ['/zh-CN/product-overview/', '/product-overview/'],
     ['/ja/product-overview/', '/ja-JP/product-overview/'],

src/lib/langParamHandler.test.ts

@@ -176,6 +176,13 @@ describe('docs language route resolution', () => {
       route('https://docs.hagicode.com/en-US/ja-JP/product-overview/', JSON.stringify({ lang: 'en-US' }), ['en-US'])
         .shouldRedirect,
     ).toBe(true);
+
+    expect(route('https://docs.hagicode.com/en/en-US/product-overview/', null, ['en-US']).targetUrl).toBe(
+      'https://docs.hagicode.com/en-US/product-overview/',
+    );
+    expect(route('https://docs.hagicode.com/en/en-US/product-overview/', null, ['en-US']).shouldRedirect).toBe(
+      true,
+    );
   });
 });
 

src/pages/en/[...slug].astro

@@ -9,6 +9,11 @@ type LegacyEnglishRouteProps = {
   redirectPath: string;
 };
 
+function toCanonicalEnglishPath(route: string): string {
+  const normalizedRoute = route.replace(/^en-US(?:\/|$)/u, '');
+  return normalizedRoute.length > 0 ? `/en-US/${normalizedRoute}/` : '/en-US/';
+}
+
 export async function getStaticPaths() {
   const docsRoot = path.resolve(path.dirname(fileURLToPath(import.meta.url)), '../../..');
   const englishDocsRoot = path.join(docsRoot, 'src/content/docs/en-US');
@@ -45,16 +50,25 @@ export async function getStaticPaths() {
   };
 
   const routes = await collectLegacyEnglishRoutes(englishDocsRoot);
+  const legacyRoutes = new Set<string>();
+
+  for (const route of routes) {
+    if (route.length === 0) {
+      continue;
+    }
+
+    legacyRoutes.add(route);
+    legacyRoutes.add(`en-US/${route}`);
+  }
 
-  return routes
-    .filter((route) => route.length > 0)
+  return Array.from(legacyRoutes)
     .sort((left, right) => left.localeCompare(right))
     .map((route) => ({
       params: {
         slug: route,
       },
       props: {
-        redirectPath: `/en-US/${route}/`,
+        redirectPath: toCanonicalEnglishPath(route),
       } satisfies LegacyEnglishRouteProps,
     }));
 }