fix(core,browser,react): Add react-native export condition to resolve dual ESM/CJS bundling

[antonis]

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Closes getsentry/sentry-react-native#6262

Summary

Since React Native 0.79 (April 2025), Metro enables unstable_enablePackageExports by default. @sentry/core, @sentry/browser, and @sentry/react only export import/require conditions. Due to a Metro isESMImport detection issue, some dependencies resolve to CJS while others resolve to ESM — causing both full module trees to be bundled into native apps.

This adds a react-native export condition (pointing to ESM) to all three packages. Metro includes react-native in its default condition names, so it matches first and always resolves to ESM — bypassing the import/require ambiguity.

Impact

• ~1 MB of unnecessary CJS code eliminated from every RN 0.79+ app shipped to stores
• Hermes compiles everything in the bundle — there is no dead code elimination after Metro

Bundle analysis (sentry-react-native sample app, Android)

	@sentry/core files	Bundle size
Before	338 CJS + 338 ESM = 676	5.09 MB
After	0 CJS + 338 ESM = 338	4.56 MB

Safety

The react-native condition is only recognized by Metro (React Native). It has no effect on:

• Node.js — not a recognized condition
• Webpack / esbuild / Vite — not in default condition names
• Any non-RN bundler — falls through to import/require as before

Changes

• packages/core/package.json — Add react-native condition to ., ./browser, ./server subpaths
• packages/browser/package.json — Add react-native condition to . (points to prod ESM build)
• packages/react/package.json — Add react-native condition to .

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Missing export regression test

Low Severity

This fix PR only updates package.json exports and the changelog, with no unit, integration, or E2E test in the diff that would fail without the react-native conditions and pass with them. Per SDK testing conventions for fix PRs, a regression test for Metro ESM-only resolution is recommended.

Additional Locations (2)

• packages/browser/package.json#L21-L22
• packages/react/package.json#L20-L24

 

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[chargome]

Generally LGTM but do you also need these export conditions e.g. for browser-utils and other packages that are pulled into our browser SDK?

[antonis]

Generally LGTM but do you also need these export conditions e.g. for browser-utils and other packages that are pulled into our browser SDK?

Thank you for the quick review and feedback @chargome 🙇
Updated with 78c86cc to add those defensively.

[Lms24]

Looks good to me in general! I wonder though how other packages handle this? Is it now a requirement for RN-compatible packages supporting CJS and ESM to explicitly define a react-native submodule export? If so that's fine (I have far too little context on Expo/RN to judge this 😅). If not, are there other solutions?

[antonis]

Looks good to me in general! I wonder though how other packages handle this? Is it now a requirement for RN-compatible packages supporting CJS and ESM to explicitly define a react-native submodule export? If so that's fine (I have far too little context on Expo/RN to judge this 😅). If not, are there other solutions?

I think this is more of a workaround for Metro ESM resolution issues (facebook/metro#1582) and it's cleaner to be in the JS repo than working around this in the react native SDK. RN and most of its ecosystem simply don't use dual import/require conditions, which is why they don't hit this bug.
The issue getsentry/sentry-react-native#6262 (for RN 0.79+) went unnoticed for a while till we got a public ping on this https://x.com/gabimoncha/status/2063607452403200003

[alwx]

Looks good. I guess the export regression part could be skipped for now.