fix: serve pages in SPA mode when the route also has an API handler (#2354)

Co-authored-by: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

Author: lxsmnsyc

.changeset/spa-page-api-route.md

@@ -0,0 +1,5 @@
+---
+"@solidjs/start": patch
+---
+
+Serve pages in SPA mode (`ssr: false`) when a route file exports both a page and an API handler, such as a `[...404].tsx` with a `GET`. The server treated those routes as API-only, so a `GET` that returned nothing gave a 404 for every URL the route matched.

packages/start/src/server/routes.spec.ts

@@ -0,0 +1,34 @@
+import { describe, expect, it, vi } from "vitest";
+
+const GET = { import: () => Promise.resolve({}) };
+
+// What the server file router produces for `routes/[...404].tsx` exporting
+// both a page and `GET`, with and without the page component.
+vi.mock("solid-start:routes", () => ({
+  default: [
+    {
+      path: "/*404",
+      page: true,
+      $component: { src: "routes/[...404].tsx", import: () => Promise.resolve({}) },
+      $GET: GET,
+    },
+    { path: "/spa/*404", page: true, $GET: GET },
+    { path: "/api/*rest", $GET: GET },
+  ],
+}));
+
+const { matchAPIRoute } = await import("./routes.ts");
+
+describe("matchAPIRoute", () => {
+  it("marks a route with a page and an API handler as a page", () => {
+    expect(matchAPIRoute("/missing", "GET")?.isPage).toBe(true);
+  });
+
+  it("marks it as a page in SPA builds, where the server routes have no page components", () => {
+    expect(matchAPIRoute("/spa/missing", "GET")?.isPage).toBe(true);
+  });
+
+  it("does not mark an API-only route as a page", () => {
+    expect(matchAPIRoute("/api/missing", "GET")?.isPage).toBe(false);
+  });
+});

packages/start/src/server/routes.ts

@@ -111,8 +111,9 @@ export function matchAPIRoute(
 
     if (handler === undefined) return;
 
-    // Check if this is a page route
-    const isPage = route.page === true && route.$component !== undefined;
+    // Check if this is a page route. SPA builds leave page components out of
+    // the server routes, so this can't depend on `$component`.
+    const isPage = route.page === true;
 
     // Return comprehensive route information
     return {