Fix canonical url for dynamic routes (#49512)

The `pathname` in app-render was actually "page" (e.g. `/blog/[slug]`),
with special url conventions. Instead we should use actual request url
as pathname. Rename previous `pathname` arg to `pagePath` for better
readability

Also improved the url validation

packages/next/src/server/app-render/app-render.tsx

@@ -138,11 +138,12 @@ function findDynamicParamFromRouterState(
 export async function renderToHTMLOrFlight(
   req: IncomingMessage,
   res: ServerResponse,
-  pathname: string,
+  pagePath: string,
   query: NextParsedUrlQuery,
   renderOpts: RenderOpts
 ): Promise<RenderResult> {
   const isFlight = req.headers[RSC.toLowerCase()] !== undefined
+  const pathname = validateURL(req.url)
 
   const {
     buildManifest,
@@ -699,7 +700,7 @@ export async function renderToHTMLOrFlight(
           !isValidElementType(Component)
         ) {
           throw new Error(
-            `The default export is not a React Component in page: "${pathname}"`
+            `The default export is not a React Component in page: "${page}"`
           )
         }
 
@@ -1179,7 +1180,7 @@ export async function renderToHTMLOrFlight(
               injectedCSS: new Set(),
               injectedFontPreloadTags: new Set(),
               rootLayoutIncluded: false,
-              asNotFound: pathname === '/404' || options?.asNotFound,
+              asNotFound: pagePath === '/404' || options?.asNotFound,
             })
           ).map((path) => path.slice(1)) // remove the '' (root) segment
 
@@ -1216,8 +1217,6 @@ export async function renderToHTMLOrFlight(
       Uint8Array
     > = new TransformStream()
 
-    const initialCanonicalUrl = validateURL(req.url)
-
     // Get the nonce from the incoming request if it has one.
     const csp = req.headers['content-security-policy']
     let nonce: string | undefined
@@ -1297,7 +1296,7 @@ export async function renderToHTMLOrFlight(
             {styles}
             <AppRouter
               assetPrefix={assetPrefix}
-              initialCanonicalUrl={initialCanonicalUrl}
+              initialCanonicalUrl={pathname}
               initialTree={initialTree}
               initialHead={
                 <>
@@ -1361,13 +1360,13 @@ export async function renderToHTMLOrFlight(
       )
     }
 
-    getTracer().getRootSpanAttributes()?.set('next.route', pathname)
+    getTracer().getRootSpanAttributes()?.set('next.route', pagePath)
     const bodyResult = getTracer().wrap(
       AppRenderSpan.getBodyResult,
       {
-        spanName: `render route (app) ${pathname}`,
+        spanName: `render route (app) ${pagePath}`,
         attributes: {
-          'next.route': pathname,
+          'next.route': pagePath,
         },
       },
       async ({
@@ -1497,8 +1496,8 @@ export async function renderToHTMLOrFlight(
           }
           if (err.digest === NEXT_DYNAMIC_NO_SSR_CODE) {
             warn(
-              `Entire page ${pathname} deopted into client-side rendering. https://nextjs.org/docs/messages/deopted-into-client-rendering`,
-              pathname
+              `Entire page ${pagePath} deopted into client-side rendering. https://nextjs.org/docs/messages/deopted-into-client-rendering`,
+              pagePath
             )
           }
           if (isNotFoundError(err)) {
@@ -1571,7 +1570,7 @@ export async function renderToHTMLOrFlight(
 
     const renderResult = new RenderResult(
       await bodyResult({
-        asNotFound: pathname === '/404',
+        asNotFound: pagePath === '/404',
       })
     )
 
@@ -1625,7 +1624,7 @@ export async function renderToHTMLOrFlight(
     () =>
       StaticGenerationAsyncStorageWrapper.wrap(
         staticGenerationAsyncStorage,
-        { pathname, renderOpts },
+        { pathname: pagePath, renderOpts },
         () => wrappedRender()
       )
   )

packages/next/src/server/app-render/validate-url.tsx

@@ -1,11 +1,18 @@
+const DUMMY_ORIGIN = 'http://n'
+const INVALID_URL_MESSAGE = 'Invalid request URL'
+
 export function validateURL(url: string | undefined): string {
   if (!url) {
-    throw new Error('Invalid request URL')
+    throw new Error(INVALID_URL_MESSAGE)
   }
   try {
-    new URL(url, 'http://n')
+    const parsed = new URL(url, DUMMY_ORIGIN)
+    // Avoid origin change by extra slashes in pathname
+    if (parsed.origin !== DUMMY_ORIGIN) {
+      throw new Error(INVALID_URL_MESSAGE)
+    }
     return url
   } catch {
-    throw new Error('Invalid request URL')
+    throw new Error(INVALID_URL_MESSAGE)
   }
 }

test/e2e/app-dir/metadata/app/alternates/child/[slug]/page.tsx

@@ -0,0 +1,3 @@
+export default function Page() {
+  return 'alternate-child-dynamic-slug'
+}

test/e2e/app-dir/metadata/metadata.test.ts

@@ -337,6 +337,11 @@ createNextDescribe(
           rel: 'alternate',
           href: 'https://example.com/alternates/child/de-DE',
         })
+
+        await browser.loadPage(next.url + '/alternates/child/123')
+        await matchDom('link', 'rel="canonical"', {
+          href: 'https://example.com/alternates/child/123',
+        })
       })
 
       it('should support robots tags', async () => {

test/unit/validate-url.test.ts

@@ -0,0 +1,13 @@
+import { validateURL } from 'next/dist/server/app-render/validate-url'
+
+describe('validateUrl', () => {
+  it('should return valid pathname', () => {
+    expect(validateURL('/')).toBe('/')
+    expect(validateURL('/abc')).toBe('/abc')
+  })
+
+  it('should throw for invalid pathname', () => {
+    expect(() => validateURL('//**y/\\')).toThrow()
+    expect(() => validateURL('//google.com')).toThrow()
+  })
+})