Fix metadata json manifest convention (#62615)

### What

Change from processing the file with `next-metatdata-route-loader`
directly into passing the file as loader query, and leave an empty
resource file for it. This will resolve the error that users were seeing
with `manifest.json` convention.

```
Import trace for requested module:
../../../../packages/next/dist/build/webpack/loaders/next-metadata-route-loader.js?page=%2Fmanifest.jso
n%2Froute&isDynamic=0!./app/manifest.json?__next_metadata_route__
getStaticAssetRouteCode page /manifest.json/route this.resourcePath /Users/huozhi/workspace/next.js/tes
t/e2e/app-dir/metadata-json-manifest/app/manifest.json
```

### Why

I looked at the loader process that the final resource processed by
webpack is `json!next-metadata-route-loader...`, which means the builtin
json loader processing json file after the metadata route loader. I
didn't get chance to solve the ordering issue, so I changed the
resourcePath to empty "", and pass the file path as query into the
loader to avoid json-loader processing it after transpilation.


Fixes #59923

Closes NEXT-2630
Closes NEXT-2439

packages/next/src/build/webpack/loaders/next-app-loader.ts

@@ -124,8 +124,9 @@ async function createAppRouteCode({
 
     resolvedPagePath = `next-metadata-route-loader?${stringify({
       page,
+      filePath: resolvedPagePath,
       isDynamic: isDynamic ? '1' : '0',
-    })}!${resolvedPagePath}${`?${WEBPACK_RESOURCE_QUERIES.metadataRoute}`}`
+    })}!?${WEBPACK_RESOURCE_QUERIES.metadataRoute}`
   }
 
   const pathname = new AppPathnameNormalizer().normalize(page)

packages/next/src/build/webpack/loaders/next-metadata-route-loader.ts

@@ -22,6 +22,7 @@ const cacheHeader = {
 
 type MetadataRouteLoaderOptions = {
   page: string
+  filePath: string
   isDynamic: '1' | '0'
 }
 
@@ -46,7 +47,6 @@ function getContentType(resourcePath: string) {
   return 'text/plain'
 }
 
-// Strip metadata resource query string from `import.meta.url` to make sure the fs.readFileSync get the right path.
 async function getStaticAssetRouteCode(
   resourcePath: string,
   fileBaseName: string
@@ -58,6 +58,7 @@ async function getStaticAssetRouteCode(
       ? cacheHeader.none
       : cacheHeader.longCache
   const code = `\
+/* static asset route */
 import { NextResponse } from 'next/server'
 
 const contentType = ${JSON.stringify(getContentType(resourcePath))}
@@ -82,6 +83,7 @@ export const dynamic = 'force-static'
 
 function getDynamicTextRouteCode(resourcePath: string) {
   return `\
+/* dynamic asset route */
 import { NextResponse } from 'next/server'
 import handler from ${JSON.stringify(resourcePath)}
 import { resolveRouteData } from 'next/dist/build/webpack/loaders/metadata/resolve-route-data'
@@ -108,6 +110,7 @@ export async function GET() {
 // <metadata-image>/[id]/route.js
 function getDynamicImageRouteCode(resourcePath: string) {
   return `\
+/* dynamic image route */
 import { NextResponse } from 'next/server'
 import * as userland from ${JSON.stringify(resourcePath)}
 
@@ -159,6 +162,7 @@ async function getDynamicSiteMapRouteCode(
     page.includes('[__metadata_id__]')
   ) {
     staticGenerationCode = `\
+/* dynamic sitemap route */ 
 export async function generateStaticParams() {
   const sitemaps = generateSitemaps ? await generateSitemaps() : []
   const params = []
@@ -232,26 +236,25 @@ ${staticGenerationCode}
 `
   return code
 }
-// `import.meta.url` is the resource name of the current module.
+
 // When it's static route, it could be favicon.ico, sitemap.xml, robots.txt etc.
 // TODO-METADATA: improve the cache control strategy
 const nextMetadataRouterLoader: webpack.LoaderDefinitionFunction<MetadataRouteLoaderOptions> =
   async function () {
-    const { resourcePath } = this
-    const { page, isDynamic } = this.getOptions()
-    const { name: fileBaseName } = getFilenameAndExtension(resourcePath)
+    const { page, isDynamic, filePath } = this.getOptions()
+    const { name: fileBaseName } = getFilenameAndExtension(filePath)
 
     let code = ''
     if (isDynamic === '1') {
       if (fileBaseName === 'robots' || fileBaseName === 'manifest') {
-        code = getDynamicTextRouteCode(resourcePath)
+        code = getDynamicTextRouteCode(filePath)
       } else if (fileBaseName === 'sitemap') {
-        code = await getDynamicSiteMapRouteCode(resourcePath, page, this)
+        code = await getDynamicSiteMapRouteCode(filePath, page, this)
       } else {
-        code = getDynamicImageRouteCode(resourcePath)
+        code = getDynamicImageRouteCode(filePath)
       }
     } else {
-      code = await getStaticAssetRouteCode(resourcePath, fileBaseName)
+      code = await getStaticAssetRouteCode(filePath, fileBaseName)
     }
 
     return code

test/e2e/app-dir/metadata-json-manifest/app/layout.js

@@ -0,0 +1,12 @@
+export const metadata = {
+  title: 'Next.js',
+  description: 'Generated by Next.js',
+}
+
+export default function RootLayout({ children }) {
+  return (
+    <html lang="en">
+      <body>{children}</body>
+    </html>
+  )
+}

test/e2e/app-dir/metadata-json-manifest/app/manifest.json

@@ -0,0 +1,6 @@
+{
+  "name": "My Next.js Application",
+  "short_name": "Next.js App",
+  "description": "An application built with Next.js",
+  "start_url": "/"
+}

test/e2e/app-dir/metadata-json-manifest/app/page.js

@@ -0,0 +1,3 @@
+export default function page() {
+  return 'page.js'
+}

test/e2e/app-dir/metadata-json-manifest/index.test.ts

@@ -0,0 +1,22 @@
+import { createNextDescribe } from 'e2e-utils'
+
+createNextDescribe(
+  'app-dir metadata-json-manifest',
+  {
+    files: __dirname,
+    skipDeployment: true,
+  },
+  ({ next }) => {
+    it('should support metadata.json manifest', async () => {
+      const response = await next.fetch('/manifest.json')
+      expect(response.status).toBe(200)
+      const json = await response.json()
+      expect(json).toEqual({
+        name: 'My Next.js Application',
+        short_name: 'Next.js App',
+        description: 'An application built with Next.js',
+        start_url: '/',
+      })
+    })
+  }
+)