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structuredClone invokes custom Map and Set iterators #58222
Description
Description
The React Native structuredClone polyfill traverses Map and Set values with for...of. An own Symbol.iterator override is therefore executed and can change the cloned contents or abort cloning, even though structured cloning should read the built-in collection data from internal slots.
Expected behavior
Map and Set cloning should ignore user iterator overrides and clone their real built-in entries, matching native structuredClone.
React Native Version
0.87.1 and current main
Affected Platforms
JavaScript runtime - All
Activity
react-native-bot commentedon Aug 30, 2026
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Missing reproducer: We could not detect a reproducible example in your issue report. Reproducers are mandatory and we can accept only one of those as a valid reproducer:
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react-native-bot commentedon Sep 24, 2026
This issue is waiting for author's feedback since 24 days. Please provide the requested feedback or this will be closed in 7 days.
OskarEichler commentedon Oct 2, 2026
Added the requested runnable RNTester Playground in #58806. Open Playground and press Run reproducers; the result for #58222 is labeled separately.
Verified using the native Hermes/Fabric Fantom runner on main
cd2de187e8878119896159371225acbb9dfa5d9c. The Map iterator override case still fails withError: user iterator ran.This is a constructed example based on the source audit, not a claimed production incident. The PR includes the exact native verification driver and results.