feat(nuxt): Implement server middleware instrumentation

[logaretm]

This pull request introduces instrumentation for Nuxt middleware, ensuring that all middleware handlers are automatically wrapped with tracing and error reporting functionality. The integration is achieved through build-time transformation.

recap:

• Adds a new build-time Rollup plugin (middlewareInstrumentationPlugin) that automatically wraps all detected middleware handlers with Sentry instrumentation during the Nitro build process.
• Implements the wrapMiddlewareHandler utility, which wraps middleware handlers to start a Sentry span, capture request data, record exceptions, and flush events in serverless environments.
• Updates the Nuxt module setup to inject Sentry middleware imports and instrumentation hooks during initialization, ensuring the new tracing logic is included in server builds.

---

Note

Adds build-time wrapping of Nuxt server middleware with Sentry spans and error capture, plus Nuxt 3/4 e2e and unit tests.

• SDK/Runtime:
  • Implement wrapMiddlewareHandlerWithSentry in packages/nuxt/src/runtime/hooks/wrapMiddlewareHandler.ts to start spans, set attributes (op, origin, route, method, headers), handle hook arrays (onRequest, onBeforeResponse), and capture errors.
  • Add middleware build-time transformation via packages/nuxt/src/vite/middlewareConfig.ts (server import + Rollup plugin to wrap defineEventHandler/eventHandler).
  • Integrate instrumentation in packages/nuxt/src/module.ts by calling addMiddlewareImports and addMiddlewareInstrumentation during Nitro init when server config is present.
• Tests:
  • Add e2e apps and Playwright tests for Nuxt 3 and Nuxt 4 (dev-packages/e2e-tests/test-applications/nuxt-{3,4}) covering span creation, attributes, parent-child relationships, and error propagation across hooks and arrays.
  • Add unit tests for wrapper behavior in packages/nuxt/test/runtime/hooks/wrapMiddlewareHandler.test.ts.

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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.

Scenario	Requests/s	% of Baseline	Prev. Requests/s	Change %
GET Baseline	8,588	-	8,926	-4%
GET With Sentry	1,338	16%	1,388	-4%
GET With Sentry (error only)	6,109	71%	6,167	-1%
POST Baseline	1,197	-	1,192	+0%
POST With Sentry	528	44%	521	+1%
POST With Sentry (error only)	1,063	89%	1,034	+3%
MYSQL Baseline	3,338	-	3,366	-1%
MYSQL With Sentry	513	15%	468	+10%
MYSQL With Sentry (error only)	2,754	83%	2,732	+1%

View base workflow run

[s1gr1d]

Super nice! I like this approach.