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The Wire · Showcase

REACT NATIVE CLEANS HOUSE, JEST REVERTS WATCHER EXPERIMENT

By RepoJournal · Filed · About Meta

React Native dropped deprecated DisplayMetrics APIs while Jest pulled the plug on a half-baked watcher backend, then pivoted to consolidate file traversal into a single shared implementation.

React Native shipped the removal of `getWindowDisplayMetrics` and related DisplayMetricsHolder APIs [1], finally closing out a deprecation cycle that's been sitting on the books since 0.87. If you're still calling these methods on Android, your builds will break on next upgrade. Jest had a rougher day. The team merged a new `haste.backend` option to support Parcel watcher [3], then immediately reverted it [3] after realizing the implementation wasn't ready for production. That's the right call, but it signals internal friction on the file-watching strategy. What's shipping instead is a cleaner win: consolidating Jest's two hand-rolled directory walkers and the separate `walker` npm dependency into a single `fdir`-based implementation [2]. This removes duplicate traversal logic across `crawlers/node.ts`, `watchers/common.js`, and `FSEventsWatcher.ts`, cutting maintenance surface and likely improving performance.

Action items

References

  1. [1] Remove getWindowDisplayMetrics from DisplayMetricsHolder (#56635) facebook/react-native
  2. [2] chore(haste-map): replace `walker` and hand-rolled traversal with `fdir` ↗ facebook/jest
  3. [3] Revert "feat(haste-map): add haste.backend option (#16184)" ↗ facebook/jest

FAQ

What changed in Meta on May 17, 2026?
React Native dropped deprecated DisplayMetrics APIs while Jest pulled the plug on a half-baked watcher backend, then pivoted to consolidate file traversal into a single shared implementation.
What should Meta teams do about it?
Update Android code calling DisplayMetricsHolder.getWindowDisplayMetrics before next React Native upgrade • Monitor Jest's next release for the fdir consolidation and test file watching in your CI environment
Which Meta repositories shipped on May 17, 2026?
facebook/react-native, facebook/jest

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