fix(@angular/ssr): prioritize the first matching route over subsequent ones

Ensures that the SSR router gives precedence to the first matching route, addressing the issue where later conflicting routes.

This change prevents the incorrect prioritization of routes and ensures the intended route is matched first, aligning routing behavior.

Closes: #29539

Author: alan-agius4

packages/angular/ssr/src/routes/ng-routes.ts

@@ -603,7 +603,6 @@ export async function getRoutesFromAngularRouterConfig(
     // Wait until the application is stable.
     await applicationRef.whenStable();
 
-    const routesResults: RouteTreeNodeMetadata[] = [];
     const errors: string[] = [];
 
     let baseHref =
@@ -627,11 +626,12 @@ export async function getRoutesFromAngularRouterConfig(
     if (errors.length) {
       return {
         baseHref,
-        routes: routesResults,
+        routes: [],
         errors,
       };
     }
 
+    const routesResults: RouteTreeNodeMetadata[] = [];
     if (router.config.length) {
       // Retrieve all routes from the Angular router configuration.
       const traverseRoutes = traverseRoutesConfig({
@@ -645,11 +645,19 @@ export async function getRoutesFromAngularRouterConfig(
         entryPointToBrowserMapping,
       });
 
-      for await (const result of traverseRoutes) {
-        if ('error' in result) {
-          errors.push(result.error);
-        } else {
-          routesResults.push(result);
+      const seenRoutes: Set<string> = new Set();
+      for await (const routeMetadata of traverseRoutes) {
+        if ('error' in routeMetadata) {
+          errors.push(routeMetadata.error);
+          continue;
+        }
+
+        // If a result already exists for the exact same route, subsequent matches should be ignored.
+        // This aligns with Angular's app router behavior, which prioritizes the first route.
+        const routePath = routeMetadata.route;
+        if (!seenRoutes.has(routePath)) {
+          routesResults.push(routeMetadata);
+          seenRoutes.add(routePath);
         }
       }
 

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

@@ -636,4 +636,38 @@ describe('extractRoutesAndCreateRouteTree', () => {
     expect(errors).toHaveSize(0);
     expect(routeTree.toObject()).toHaveSize(2);
   });
+
+  it('should give precedence to the first matching route over subsequent ones', async () => {
+    setAngularAppTestingManifest(
+      [
+        {
+          path: '',
+          children: [
+            { path: 'home', component: DummyComponent },
+            { path: '**', component: DummyComponent },
+          ],
+        },
+        // The following routes should be ignored due to Angular's routing behavior:
+        // - ['', '**'] and ['**'] are equivalent, and the first match takes precedence.
+        // - ['', 'home'] and ['home'] are equivalent, and the first match takes precedence.
+        {
+          path: 'home',
+          redirectTo: 'never',
+        },
+        {
+          path: '**',
+          redirectTo: 'never',
+        },
+      ],
+      [{ path: '**', renderMode: RenderMode.Server }],
+    );
+
+    const { routeTree, errors } = await extractRoutesAndCreateRouteTree({ url });
+    expect(errors).toHaveSize(0);
+    expect(routeTree.toObject()).toEqual([
+      { route: '/', renderMode: RenderMode.Server },
+      { route: '/home', renderMode: RenderMode.Server },
+      { route: '/**', renderMode: RenderMode.Server },
+    ]);
+  });
 });