fix(@angular/ssr): preserve trailing slashes in query and fragment of redirect URLs

In redirect URLs, trailing slashes in query parameters or hash fragments
should be preserved, while the path portion before the query or fragment
continues to be normalized.

Fixes #34511

Author: alan-agius4

packages/angular/ssr/src/utils/url.ts

@@ -93,13 +93,16 @@ export function addTrailingSlash(url: string): string {
  * ```js
  * joinUrlParts('path/', '/to/resource'); // '/path/to/resource'
  * joinUrlParts('/path/', 'to/resource'); // '/path/to/resource'
+ * joinUrlParts('/base/', '/login/?next=/a/'); // '/base/login?next=/a/'
  * joinUrlParts('', ''); // '/'
  * ```
  */
 export function joinUrlParts(...parts: string[]): string {
   const normalizedParts: string[] = [];
+  let suffix = '';
 
-  for (const part of parts) {
+  for (let i = 0, len = parts.length; i < len; i++) {
+    const part = parts[i];
     if (part === '') {
       // Skip any empty parts
       continue;
@@ -108,6 +111,22 @@ export function joinUrlParts(...parts: string[]): string {
     let start = 0;
     let end = part.length;
 
+    if (i === len - 1) {
+      const queryIndex = part.indexOf('?');
+      const hashIndex = part.indexOf('#');
+      const suffixIndex =
+        queryIndex === -1
+          ? hashIndex
+          : hashIndex === -1
+            ? queryIndex
+            : Math.min(queryIndex, hashIndex);
+
+      if (suffixIndex !== -1) {
+        suffix = part.slice(suffixIndex);
+        end = suffixIndex;
+      }
+    }
+
     // Use "Pointers" to avoid intermediate slices
     while (start < end && part[start] === '/') {
       start++;
@@ -122,7 +141,7 @@ export function joinUrlParts(...parts: string[]): string {
     }
   }
 
-  return addLeadingSlash(normalizedParts.join('/'));
+  return addLeadingSlash(normalizedParts.join('/')) + suffix;
 }
 
 /**

packages/angular/ssr/test/app_spec.ts

@@ -96,6 +96,14 @@ describe('AngularServerApp', () => {
           path: 'redirect-query-placeholder',
           redirectTo: '/home?q=:term&id=:missing&static=value',
         },
+        {
+          path: 'redirect-query-trailing-slash',
+          redirectTo: '/home?next=/a/',
+        },
+        {
+          path: 'redirect-fragment-trailing-slash',
+          redirectTo: '/home#section/',
+        },
         {
           path: 'redirect-to-function',
           redirectTo: () => 'home',
@@ -282,6 +290,20 @@ describe('AngularServerApp', () => {
         expect(response?.status).toBe(302);
       });
 
+      it('should preserve trailing slashes in query parameters and fragments of redirect targets', async () => {
+        const queryResponse = await app.handle(
+          new Request('http://localhost/redirect-query-trailing-slash'),
+        );
+        expect(queryResponse?.headers.get('location')).toBe('/home?next=/a/');
+        expect(queryResponse?.status).toBe(302);
+
+        const fragmentResponse = await app.handle(
+          new Request('http://localhost/redirect-fragment-trailing-slash'),
+        );
+        expect(fragmentResponse?.headers.get('location')).toBe('/home#section/');
+        expect(fragmentResponse?.status).toBe(302);
+      });
+
       it('should handle request abortion gracefully', async () => {
         const controller = new AbortController();
         const request = new Request('http://localhost/home', { signal: controller.signal });

packages/angular/ssr/test/routes/ng-routes_spec.ts

@@ -812,6 +812,31 @@ describe('extractRoutesAndCreateRouteTree', () => {
     ]);
   });
 
+  it('should preserve trailing slashes in query parameters and fragments of absolute redirect targets', async () => {
+    setAngularAppTestingManifest(
+      [
+        { path: 'query-slash', redirectTo: '/login?next=/a/' },
+        { path: 'fragment-slash', redirectTo: '/login#section/' },
+        { path: 'path-and-query-slash', redirectTo: '/login/?next=/a/' },
+        { path: 'login', component: DummyComponent },
+      ],
+      [{ path: '**', renderMode: RenderMode.Server }],
+    );
+
+    const { routeTree, errors } = await extractRoutesAndCreateRouteTree({ url });
+    expect(errors).toHaveSize(0);
+    expect(routeTree.toObject()).toEqual([
+      { route: '/query-slash', renderMode: RenderMode.Server, redirectTo: '/login?next=/a/' },
+      { route: '/fragment-slash', renderMode: RenderMode.Server, redirectTo: '/login#section/' },
+      {
+        route: '/path-and-query-slash',
+        renderMode: RenderMode.Server,
+        redirectTo: '/login?next=/a/',
+      },
+      { route: '/login', renderMode: RenderMode.Server },
+    ]);
+  });
+
   it('should not resolve parameterized routes for SSG when `invokeGetPrerenderParams` is false', async () => {
     setAngularAppTestingManifest(
       [

packages/angular/ssr/test/utils/url_spec.ts

@@ -112,6 +112,18 @@ describe('URL Utils', () => {
     it('should handle parts containing only slashes', () => {
       expect(joinUrlParts('//', '///')).toBe('/');
     });
+
+    it('should preserve trailing slashes in query parameters and fragments', () => {
+      expect(joinUrlParts('/', '/login?next=/a/')).toBe('/login?next=/a/');
+      expect(joinUrlParts('/', '/login#section/')).toBe('/login#section/');
+      expect(joinUrlParts('/base/', '/foo/?next=/a/#section/')).toBe('/base/foo?next=/a/#section/');
+      expect(joinUrlParts('/base/', '/login/#section?next=/a/')).toBe(
+        '/base/login#section?next=/a/',
+      );
+      expect(joinUrlParts('/base/', '/?next=/a/')).toBe('/base?next=/a/');
+      expect(joinUrlParts('/', '/?next=/a/')).toBe('/?next=/a/');
+      expect(joinUrlParts('', '///evil.com?a=/')).toBe('/evil.com?a=/');
+    });
   });
 
   describe('stripIndexHtmlFromURL', () => {