Return a 404 when paring the route fails (#3860)

* return a 404 when paring the route fails

* add a playwright test for fullstack routing status codes

* Fix new playwright test

* document SSRError

* Make SSRError public and fix clippy

* Move the error display bound to the routable trait

* fix clippy

* return a more generic 404 message

* fix router tests

packages/playwright-tests/fullstack-routing.spec.js

@@ -0,0 +1,53 @@
+// @ts-check
+const { test, expect } = require("@playwright/test");
+
+// Wait for the build to finish
+async function waitForBuild(request) {
+  for (let i = 0; i < 10; i++) {
+    const build = await request.get("http://localhost:8888");
+    let text = await build.text();
+    if (!text.includes("Backend connection failed")) {
+      return;
+    }
+    await new Promise((r) => setTimeout(r, 1000));
+  }
+}
+
+// The home and id routes should return 200
+test("home route", async ({ request }) => {
+  await waitForBuild(request);
+  const response = await request.get("http://localhost:8888");
+
+  expect(response.status()).toBe(200);
+
+  const text = await response.text();
+  expect(text).toContain("Home");
+});
+
+test("blog route", async ({ request }) => {
+  await waitForBuild(request);
+  const response = await request.get("http://localhost:8888/blog/123");
+
+  expect(response.status()).toBe(200);
+
+  const text = await response.text();
+  expect(text).toContain("id: 123");
+});
+
+// The error route should return 500
+test("error route", async ({ request }) => {
+  await waitForBuild(request);
+  const response = await request.get("http://localhost:8888/error");
+
+  expect(response.status()).toBe(500);
+});
+
+// An unknown route should return 404
+test("unknown route", async ({ request }) => {
+  await waitForBuild(request);
+  const response = await request.get(
+    "http://localhost:8888/this-route-does-not-exist"
+  );
+
+  expect(response.status()).toBe(404);
+});