build(rollup-utils): Skip bare side-effect imports for sideEffects: false externals - #23674
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Lms24
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…false` externals Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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For CF integration tests there were a lot of warnings printed:
Root cause
treeshake.moduleSideEffectsindev-packages/rollup-utils/npmHelpers.mjstold Rollup that every external module has side effects. When Rollup tree-shakes away all named bindings of such an external, it keeps a bare side-effect import to preserve those effects. That import contradicts the dependency's own"sideEffects": false, which is what the consuming bundler reports.The Cloudflare instance is reachable from a single line in
packages/cloudflare/src/sdk.ts:_clearGlobalClientCache is a test-only helper that no entrypoint reaches, so Rollup drops the re-export. clientCache.ts imports GLOBAL_OBJ from @sentry/core, and Rollup hoists that external dependency into sdk.js as a bare import to keep its supposed side effects alive.
#22015 already hit this and special-cased @sentry/conventions. That patched one instance rather than the mechanism, so the next package to trip it, @sentry/core, brought the warnings straight back.
Solution
Now we check for the key
sideEffectsin the respesctitivepackage.json. If there issideEffectsset it will take its value, and if there is non then we assume there are side effects, just as before. With that the warnings are gone.