[kinyoklion]

Summary

TestData kept flags, segments and flag builders in plain objects, so a flag key that is a built-in object member did not work:

• flag() threw this._flagBuilders[key].clone is not a function for keys such as constructor, toString or __proto__.
• update() read the version of the inherited member, so such a flag got the version NaN.
• A flag or segment named __proto__ was dropped, by assignment and by the object spread in TestDataSource.

These objects now have no prototype. A new unit test configures and changes flags with these keys and reads them from the store.

_{Opened from termag}

SDK-3497

---

Note

Overview
TestData now stores flags, segments, and flag builders in null-prototype objects (Object.create(null)) instead of {}, so keys like __proto__, constructor, hasOwnProperty, and toString behave as normal flag keys instead of colliding with inherited properties.

TestDataSource applies the same pattern when cloning initial flags/segments (Object.assign(Object.create(null), …) instead of object spread), so __proto__ and similar keys are not lost during copy.

A new integration test configures and updates flags with those keys and asserts they land in the feature store with the expected version and variation.

^{Reviewed by Cursor Bugbot for commit b6f5a12. Bugbot is set up for automated code reviews on this repo. Configure here.}

[github-actions]

@launchdarkly/js-sdk-common size report
This is the brotli compressed size of the ESM build.
Compressed size: 32497 bytes
Compressed size limit: 32500
Uncompressed size: 153345 bytes

[github-actions]

@launchdarkly/js-client-sdk size report
This is the brotli compressed size of the ESM build.
Compressed size: 34545 bytes
Compressed size limit: 35000
Uncompressed size: 123262 bytes

[github-actions]

@launchdarkly/js-client-sdk-common size report
This is the brotli compressed size of the ESM build.
Compressed size: 26066 bytes
Compressed size limit: 44000
Uncompressed size: 168326 bytes