test(e2e): Add Bun Express test app (#24306)

Adds a dedicated Bun + Express E2E application covering automatic
request tracing and error capture. The app exercises both a
parameterized success route and an exception route, asserting Express
handler spans, route naming, status propagation, the Bun runtime
context, and trace correlation.

The app is built with `sentryBunPlugin` because Express instrumentation
under Bun relies on build-time diagnostics-channel injection. The SDK
and Express remain external so the app validates the normal package
boundary, while CI now installs its pinned Bun version for this matrix
entry.

The targeted `bun-express` E2E run passes both Playwright cases on Bun
1.3.14. `yarn format`, `yarn build:dev`, and `yarn build:tarball` also
complete successfully. The full local lint and unit-suite runs still
surface pre-existing environment/baseline failures outside the files
changed here; CI will provide the authoritative full-suite result.

Fixes #12732

Co-authored-by: OpenAI Codex <codex@openai.com>

Author: nabi-noor

.github/workflows/build.yml

@@ -1056,7 +1056,7 @@ jobs:
       - name: Set up Bun
         if:
           contains(fromJSON('["node-exports-test-app","nextjs-16-bun", "elysia-bun", "elysia-bun-static", "hono-4",
-          "bun-bytecode", "bun-mysql"]'), matrix.test-application)
+          "bun-bytecode", "bun-express", "bun-mysql"]'), matrix.test-application)
         uses: oven-sh/setup-bun@v2
         with:
           bun-version: '1.3.14'

dev-packages/e2e-tests/test-applications/bun-express/.gitignore

@@ -0,0 +1 @@
+dist

dev-packages/e2e-tests/test-applications/bun-express/build.ts

@@ -0,0 +1,20 @@
+// @ts-ignore -- subpath export resolved by Bun at runtime; the package
+// tsconfig's node module resolution can't see `exports` subpaths.
+import { sentryBunPlugin } from '@sentry/bun/plugin';
+import { join } from 'path';
+
+void (async () => {
+  const result = await Bun.build({
+    entrypoints: [join(__dirname, 'src/app.ts')],
+    target: 'bun',
+    outdir: join(__dirname, 'dist'),
+    external: ['@sentry/bun', 'express'],
+    plugins: [sentryBunPlugin()],
+  });
+
+  if (!result.success) {
+    // oxlint-disable-next-line no-console
+    console.error('BUILD_FAILED', result.logs);
+    process.exit(1);
+  }
+})();

dev-packages/e2e-tests/test-applications/bun-express/package.json

@@ -0,0 +1,26 @@
+{
+  "name": "bun-express",
+  "version": "1.0.0",
+  "private": true,
+  "type": "module",
+  "scripts": {
+    "start": "bun run dist/app.js",
+    "test": "playwright test",
+    "clean": "npx rimraf node_modules pnpm-lock.yaml dist",
+    "test:build": "pnpm install && bun run build.ts",
+    "test:assert": "pnpm test"
+  },
+  "dependencies": {
+    "@sentry/bun": "latest || *",
+    "express": "^5.1.0"
+  },
+  "devDependencies": {
+    "@playwright/test": "~1.56.0",
+    "@sentry-internal/test-utils": "link:../../../test-utils",
+    "@types/express": "^5.0.0",
+    "bun-types": "^1.2.9"
+  },
+  "volta": {
+    "extends": "../../package.json"
+  }
+}

dev-packages/e2e-tests/test-applications/bun-express/playwright.config.mjs

@@ -0,0 +1,5 @@
+import { getPlaywrightConfig } from '@sentry-internal/test-utils';
+
+export default getPlaywrightConfig({
+  startCommand: 'pnpm start',
+});

dev-packages/e2e-tests/test-applications/bun-express/src/app.ts

@@ -0,0 +1,28 @@
+import * as Sentry from '@sentry/bun';
+import express from 'express';
+
+Sentry.init({
+  environment: 'qa',
+  dsn: process.env.E2E_TEST_DSN,
+  tunnel: 'http://localhost:3031/',
+  tracesSampleRate: 1,
+});
+
+const app = express();
+
+app.get('/test-param/:id', (request, response) => {
+  response.json({ id: request.params.id });
+});
+
+app.get('/test-exception/:id', request => {
+  throw new Error(`This is an exception with id ${request.params.id}`);
+});
+
+app.use((_error, _request, response, _next) => {
+  response.status(500).send('Internal Server Error');
+});
+
+app.listen(3030, () => {
+  // oxlint-disable-next-line no-console
+  console.log('Bun Express app listening on port 3030');
+});

dev-packages/e2e-tests/test-applications/bun-express/start-event-proxy.mjs

@@ -0,0 +1,6 @@
+import { startEventProxyServer } from '@sentry-internal/test-utils';
+
+startEventProxyServer({
+  port: 3031,
+  proxyServerName: 'bun-express',
+});

dev-packages/e2e-tests/test-applications/bun-express/tests/errors.test.ts

@@ -0,0 +1,33 @@
+import { expect, test } from '@playwright/test';
+import { collectStreamedSpansUntilSegment, waitForError } from '@sentry-internal/test-utils';
+
+test('captures an error thrown in an Express route', async ({ baseURL }) => {
+  const errorEventPromise = waitForError('bun-express', event => {
+    return !event.type && event.exception?.values?.[0]?.value === 'This is an exception with id 123';
+  });
+  const spansPromise = collectStreamedSpansUntilSegment('bun-express', 'GET /test-exception/:id');
+
+  const response = await fetch(`${baseURL}/test-exception/123`);
+
+  const errorEvent = await errorEventPromise;
+  const spans = await spansPromise;
+
+  expect(response.status).toBe(500);
+  expect(errorEvent.exception?.values).toEqual([
+    expect.objectContaining({
+      value: 'This is an exception with id 123',
+      mechanism: {
+        type: 'auto.http.express',
+        handled: false,
+      },
+    }),
+  ]);
+  expect(errorEvent.transaction).toBe('GET /test-exception/:id');
+  expect(errorEvent.contexts?.runtime?.name).toBe('bun');
+
+  const rootSpan = spans.find(span => span.is_segment);
+  expect(rootSpan?.name).toBe('GET /test-exception/:id');
+  expect(rootSpan?.status).toBe('error');
+  expect(rootSpan?.attributes['http.response.status_code']?.value).toBe(500);
+  expect(errorEvent.contexts?.trace?.trace_id).toBe(rootSpan?.trace_id);
+});

dev-packages/e2e-tests/test-applications/bun-express/tests/spans.test.ts

@@ -0,0 +1,30 @@
+import { expect, test } from '@playwright/test';
+import { collectStreamedSpansUntilSegment, getSpanOp } from '@sentry-internal/test-utils';
+
+test('instruments an Express route under Bun', async ({ baseURL }) => {
+  const spansPromise = collectStreamedSpansUntilSegment('bun-express', 'GET /test-param/:id');
+
+  const response = await fetch(`${baseURL}/test-param/123`);
+  const spans = await spansPromise;
+
+  expect(response.status).toBe(200);
+  expect(await response.json()).toEqual({ id: '123' });
+
+  const rootSpan = spans.find(span => span.is_segment);
+  expect(rootSpan?.name).toBe('GET /test-param/:id');
+  expect(rootSpan && getSpanOp(rootSpan)).toBe('http.server');
+  expect(rootSpan?.status).toBe('ok');
+  expect(rootSpan?.attributes['sentry.segment.name.source']?.value).toBe('route');
+
+  expect(spans).toContainEqual(
+    expect.objectContaining({
+      name: '/test-param/:id',
+      attributes: expect.objectContaining({
+        'sentry.origin': { value: 'auto.http.express', type: 'string' },
+        'sentry.op': { value: 'handler', type: 'string' },
+        'http.route': { value: '/test-param/:id', type: 'string' },
+        'express.type': { value: 'request_handler', type: 'string' },
+      }),
+    }),
+  );
+});

dev-packages/e2e-tests/test-applications/bun-express/tsconfig.json

@@ -0,0 +1,11 @@
+{
+  "compilerOptions": {
+    "types": ["bun-types"],
+    "esModuleInterop": true,
+    "lib": ["es2020"],
+    "strict": true,
+    "outDir": "dist",
+    "skipLibCheck": true
+  },
+  "include": ["src/**/*.ts", "build.ts"]
+}