From 6448f80bfb4a8900ca78857917314bd15fa4144d Mon Sep 17 00:00:00 2001
From: Alan Agius <alanagius@google.com>
Date: Thu, 30 Jan 2025 10:09:47 +0000
Subject: [PATCH] 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
---
 packages/angular/ssr/src/routes/ng-routes.ts  | 22 ++++++++----
 .../angular/ssr/test/routes/ng-routes_spec.ts | 34 +++++++++++++++++++
 2 files changed, 49 insertions(+), 7 deletions(-)

diff --git a/packages/angular/ssr/src/routes/ng-routes.ts b/packages/angular/ssr/src/routes/ng-routes.ts
index 62b202d406f7..97d77e072c4b 100644
--- a/packages/angular/ssr/src/routes/ng-routes.ts
+++ b/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);
         }
       }
 
diff --git a/packages/angular/ssr/test/routes/ng-routes_spec.ts b/packages/angular/ssr/test/routes/ng-routes_spec.ts
index 37d4bf890a06..ed600d424e0a 100644
--- a/packages/angular/ssr/test/routes/ng-routes_spec.ts
+++ b/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 },
+    ]);
+  });
 });