feat(tanstackstart-react): Auto-instrument global middleware

[nicohrubec]

This PR adds automatic instrumentation for global request and function middleware in TanStack Start applications.

Overview

The sentryTanstackStart Vite plugin now automatically wraps requestMiddleware and functionMiddleware arrays in createStart() with Sentry instrumentation. This is done via a source code transformation during the build that converts:

createStart({
  requestMiddleware: [myMiddleware],
  functionMiddleware: [anotherMiddleware],
});

into:

import { wrapMiddlewaresWithSentry } from '@sentry/tanstackstart-react';

createStart({
  requestMiddleware: wrapMiddlewaresWithSentry({ myMiddleware }),
  functionMiddleware: wrapMiddlewaresWithSentry({ anotherMiddleware }),
});

Usage

Auto-instrumentation is enabled by default. To explicitly disable it:

// vite.config.ts
import { sentryTanstackStart } from '@sentry/tanstackstart-react';

export default defineConfig({
  plugins: [
    sentryTanstackStart({
      org: 'your-org',
      project: 'your-project',
      autoInstrumentMiddleware: false, // Disable auto-instrumentation
    }),
  ],
});

This should give users flexibility in case things go wrong.

Implementation Details

• Uses a regex-based approach to transform source files containing createStart()
• Skips transformation if the user has already manually wrapped middlewares with wrapMiddlewaresWithSentry
• Only handles simple identifier arrays (e.g., [foo, bar]), not complex expressions

Testing

• Updated E2E tests to use auto-instrumentation for global middleware
• Updated unit tests for the sentryTanstackStart plugin
• Added unit tests for autoInstrumentMiddleware

Follow-ups

Future PRs will add support for non-global request/function middleware. This PR focuses on global middleware to make it a bit easier to review. I also want to give users a bit more control by allowing them to disable auto-instrumentation on a file-level, but this doesn't make sense yet since the current implementation only patches a single file anyways.

Closes #18845

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[github-actions]

node-overhead report 🧳

Note: This is a synthetic benchmark with a minimal express app and does not necessarily reflect the real-world performance impact in an application.
⚠️ Warning: Base artifact is not the latest one, because the latest workflow run is not done yet. This may lead to incorrect results. Try to re-run all tests to get up to date results.

Scenario	Requests/s	% of Baseline	Prev. Requests/s	Change %
GET Baseline	8,493	-	9,023	-6%
GET With Sentry	1,566	18%	1,634	-4%
GET With Sentry (error only)	5,805	68%	5,919	-2%
POST Baseline	1,159	-	1,137	+2%
POST With Sentry	559	48%	550	+2%
POST With Sentry (error only)	1,017	88%	1,035	-2%
MYSQL Baseline	3,164	-	3,156	+0%
MYSQL With Sentry	324	10%	398	-19%
MYSQL With Sentry (error only)	2,519	80%	2,578	-2%

View base workflow run

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

^{Bugbot Autofix is OFF. To automatically fix reported issues with Cloud Agents, enable Autofix in the Cursor dashboard.}

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

^{Bugbot Autofix is OFF. To automatically fix reported issues with Cloud Agents, enable Autofix in the Cursor dashboard.}

[github-actions]

size-limit report 📦

⚠️ Warning: Base artifact is not the latest one, because the latest workflow run is not done yet. This may lead to incorrect results. Try to re-run all tests to get up to date results.

Path	Size	% Change	Change
@sentry/browser	25.11 kB	-	-
@sentry/browser - with treeshaking flags	23.61 kB	-	-
@sentry/browser (incl. Tracing)	41.87 kB	-	-
@sentry/browser (incl. Tracing, Profiling)	46.45 kB	-	-
@sentry/browser (incl. Tracing, Replay)	80.47 kB	-	-
@sentry/browser (incl. Tracing, Replay) - with treeshaking flags	70.16 kB	-	-
@sentry/browser (incl. Tracing, Replay with Canvas)	85.17 kB	-	-
@sentry/browser (incl. Tracing, Replay, Feedback)	97.37 kB	-	-
@sentry/browser (incl. Feedback)	41.83 kB	-	-
@sentry/browser (incl. sendFeedback)	29.79 kB	-	-
@sentry/browser (incl. FeedbackAsync)	34.79 kB	-	-
@sentry/browser (incl. Metrics)	26.21 kB	-	-
@sentry/browser (incl. Logs)	26.37 kB	-	-
@sentry/browser (incl. Metrics & Logs)	27.02 kB	-	-
@sentry/react	26.84 kB	-	-
@sentry/react (incl. Tracing)	44.09 kB	-	-
@sentry/vue	29.56 kB	-	-
@sentry/vue (incl. Tracing)	43.67 kB	-	-
@sentry/svelte	25.12 kB	-	-
CDN Bundle	27.67 kB	-	-
CDN Bundle (incl. Tracing)	42.67 kB	-	-
CDN Bundle (incl. Tracing, Logs, Metrics)	43.5 kB	-	-
CDN Bundle (incl. Tracing, Replay)	79.37 kB	-	-
CDN Bundle (incl. Tracing, Replay, Feedback)	84.81 kB	-	-
CDN Bundle (incl. Tracing, Replay, Feedback, Logs, Metrics)	85.72 kB	-	-
CDN Bundle - uncompressed	81.08 kB	-	-
CDN Bundle (incl. Tracing) - uncompressed	126.5 kB	-	-
CDN Bundle (incl. Tracing, Logs, Metrics) - uncompressed	129.33 kB	-	-
CDN Bundle (incl. Tracing, Replay) - uncompressed	243.03 kB	-	-
CDN Bundle (incl. Tracing, Replay, Feedback) - uncompressed	255.83 kB	-	-
CDN Bundle (incl. Tracing, Replay, Feedback, Logs, Metrics) - uncompressed	258.64 kB	-	-
@sentry/nextjs (client)	46.44 kB	-	-
@sentry/sveltekit (client)	42.25 kB	-	-
@sentry/node-core	51.93 kB	+0.06%	+27 B 🔺
@sentry/node	162.19 kB	+0.02%	+30 B 🔺
@sentry/node - without tracing	93.35 kB	+0.03%	+21 B 🔺
@sentry/aws-serverless	108.85 kB	+0.02%	+21 B 🔺

View base workflow run