Preserve slashes when custom URL schemes are used in redirects

packages/next/src/shared/lib/router/utils/parse-relative-url.ts

@@ -8,6 +8,7 @@ export interface ParsedRelativeUrl {
   pathname: string
   query: ParsedUrlQuery
   search: string
+  slashes: undefined
 }
 
 /**
@@ -58,5 +59,8 @@ export function parseRelativeUrl(
     search,
     hash,
     href: href.slice(origin.length),
+    // We don't know for relative URLs at this point since we set a custom, internal
+    // base that isn't surfaced to users.
+    slashes: undefined,
   }
 }

packages/next/src/shared/lib/router/utils/parse-url.ts

@@ -12,6 +12,7 @@ export interface ParsedUrl {
   protocol?: string | null
   query: ParsedUrlQuery
   search: string
+  slashes: boolean | undefined
 }
 
 export function parseUrl(url: string): ParsedUrl {
@@ -29,5 +30,10 @@ export function parseUrl(url: string): ParsedUrl {
     protocol: parsedURL.protocol,
     query: searchParamsToUrlQuery(parsedURL.searchParams),
     search: parsedURL.search,
+    slashes:
+      parsedURL.href.slice(
+        parsedURL.protocol.length,
+        parsedURL.protocol.length + 2
+      ) === '//',
   }
 }

packages/next/src/shared/lib/router/utils/prepare-destination.test.ts

@@ -20,6 +20,7 @@ describe('parseDestination', () => {
        "pathname": "/hello/:name",
        "query": {},
        "search": "",
+       "slashes": undefined,
      }
     `)
   })
@@ -45,6 +46,7 @@ describe('parseDestination', () => {
        "protocol": "https:",
        "query": {},
        "search": "",
+       "slashes": true,
      }
     `)
   })
@@ -72,6 +74,7 @@ describe('parseDestination', () => {
          "foo": ":bar",
        },
        "search": "?foo=:bar",
+       "slashes": true,
      }
     `)
   })

packages/next/src/shared/lib/router/utils/resolve-rewrites.ts

@@ -7,6 +7,10 @@ import { normalizeLocalePath } from '../../i18n/normalize-locale-path'
 import { removeBasePath } from '../../../../client/remove-base-path'
 import { parseRelativeUrl, type ParsedRelativeUrl } from './parse-relative-url'
 
+interface ParsedAs extends Omit<ParsedRelativeUrl, 'slashes'> {
+  slashes: boolean | undefined
+}
+
 export default function resolveRewrites(
   asPath: string,
   pages: string[],
@@ -20,14 +24,14 @@ export default function resolveRewrites(
   locales?: readonly string[]
 ): {
   matchedPage: boolean
-  parsedAs: ParsedRelativeUrl
+  parsedAs: ParsedAs
   asPath: string
   resolvedHref?: string
   externalDest?: boolean
 } {
   let matchedPage = false
   let externalDest = false
-  let parsedAs = parseRelativeUrl(asPath)
+  let parsedAs: ParsedAs = parseRelativeUrl(asPath)
   let fsPathname = removeTrailingSlash(
     normalizeLocalePath(removeBasePath(parsedAs.pathname), locales).pathname
   )

test/e2e/app-dir/rewrites-redirects/next.config.js

@@ -20,6 +20,18 @@ module.exports = {
         destination: '/config-redirect-catchall-after/:path*',
         permanent: true,
       },
+      {
+        source: '/config-redirect-itms-apps-slashes',
+        destination:
+          'itms-apps://apps.apple.com/de/app/xcode/id497799835?l=en-GB&mt=12',
+        permanent: true,
+      },
+      {
+        source: '/config-redirect-itms-apps-no-slashes',
+        destination:
+          'itms-apps:apps.apple.com/de/app/xcode/id497799835?l=en-GB&mt=12',
+        permanent: true,
+      },
     ]
   },
 }

test/e2e/app-dir/rewrites-redirects/rewrites-redirects.test.ts

@@ -78,4 +78,26 @@ describe('redirects and rewrites', () => {
       expect(url.pathname).toEndWith('-after')
     })
   })
+
+  it('redirects to exotic url schemes preserving slashes', async () => {
+    const response = await next.fetch('/config-redirect-itms-apps-slashes', {
+      redirect: 'manual',
+    })
+
+    expect(response.headers.get('location')).toEqual(
+      'itms-apps://apps.apple.com/de/app/xcode/id497799835?l=en-GB&mt=12'
+    )
+    expect(response.status).toBe(308)
+  })
+
+  it('redirects to exotic url schemes without adding unwanted slashes', async () => {
+    const response = await next.fetch('/config-redirect-itms-apps-no-slashes', {
+      redirect: 'manual',
+    })
+
+    expect(response.headers.get('location')).toEqual(
+      'itms-apps:apps.apple.com/de/app/xcode/id497799835?l=en-GB&mt=12'
+    )
+    expect(response.status).toBe(308)
+  })
 })