rolldown-sentry-treeshake

Minimal repro showing that destructuring a deferred import('@sentry/react') namespace defeats Rolldown tree-shaking, dragging Session Replay / Feedback / AI instrumenters onto the critical path even when they're never used.

Switching the destructure to plain property access (sentry.x) seems to tree-shake as expected.

Run

npm install
npm run compare

This builds both entries with Vite 8 (Rolldown) and prints the comparison:

scenario           min         gzip        replay pulled in?
------------------------------------------------------------
destructure        466.1 KB    151.6 KB    YES
property-access    144.4 KB    48.2 KB     no
------------------------------------------------------------
delta: 321.6 KB min / 103.4 KB gzip removed
       3.2x smaller by switching to property access

The snippet

src/destructure.js: namespace is destructured:

void import("@sentry/react").then((sentry) => {
  const { addIntegration, tanstackRouterBrowserTracingIntegration, breadcrumbsIntegration } =
    sentry;
  addIntegration(tanstackRouterBrowserTracingIntegration(router));
  addIntegration(breadcrumbsIntegration({ fetch: true, history: true }));
});

src/property-access.js: same code, referenced via member access, which Rolldown seems to be able to tree-shake:

void import("@sentry/react").then((sentry) => {
  sentry.addIntegration(sentry.tanstackRouterBrowserTracingIntegration(router));
  sentry.addIntegration(sentry.breadcrumbsIntegration({ fetch: true, history: true }));
});

Why

Unsure, but Rolldown converts star exports using __exportAll() runtime helper, so this can get in the way of DCE. What is not clear is why destructuring affects the outcome.

Related upstream issues:

• rolldown/rolldown#7874