react / react/react-native

polyfillPromise.js imports a `promise` package that never used as `hasPromise()` is always true

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Description

Description

Currently we have a runtime check for hasPromise() that leads to bundling a dead code (promise package) in the final JS bundle

https://github.com/react/react-native/blob/eda6f4f8ecd78408fd7b535662e3c0bdeed740df/packages/react-native/Libraries/Core/polyfillPromise.js#L23-L38

hasPromise () is true by default so promise package code is never used by thousands apps in productions

Steps to reproduce

...

React Native Version

0.86.0

Affected Platforms

Runtime - Android, Runtime - iOS

Output of npx @react-native-community/cli info
System:
  OS: macOS 26.5
  CPU: (11) arm64 Apple M3 Pro
  Memory: 5.12 GB / 36.00 GB
  Shell:
    version: 4.0.1
    path: /opt/homebrew/bin/fish
Binaries:
  Node:
    version: 24.13.1
    path: /usr/local/bin/node
  Yarn:
    version: 3.6.4
    path: /opt/homebrew/bin/yarn
  npm:
    version: 11.8.0
    path: /usr/local/bin/npm
  Watchman:
    version: 2025.09.01.00
    path: /opt/homebrew/bin/watchman
Managers:
  CocoaPods:
    version: 1.16.2
    path: /Users/i/.rbenv/shims/pod
SDKs:
  iOS SDK:
    Platforms:
      - DriverKit 25.2
      - iOS 26.2
      - macOS 26.2
      - tvOS 26.2
      - visionOS 26.2
      - watchOS 26.2
  Android SDK:
    API Levels:
      - "34"
      - "35"
      - "36"
    Build Tools:
      - 33.0.1
      - 34.0.0
      - 35.0.0
      - 36.0.0
      - 37.0.0
    System Images:
      - android-34 | Android TV ARM 64 v8a
      - android-34 | Google TV ARM 64 v8a
      - android-35 | Google APIs ARM 64 v8a
      - android-35 | Google Play ARM 64 v8a
      - android-36 | Android TV ARM 64 v8a
      - android-36 | Google TV ARM 64 v8a
    Android NDK: Not Found
IDEs:
  Android Studio: 2026.1 AI-261.23567.138.2611.15646644
  Xcode:
    version: 26.2/17C52
    path: /usr/bin/xcodebuild
Languages:
  Java:
    version: 17.0.13
    path: /usr/bin/javac
  Ruby:
    version: 2.6.10
    path: /Users/i/.rbenv/shims/ruby
npmPackages:
  "@react-native-community/cli":
    installed: 20.1.0
    wanted: 20.1.0
  react:
    installed: 19.2.3
    wanted: 19.2.3
  react-native:
    installed: 0.86.0
    wanted: 0.86.0
  react-native-macos: Not Found
npmGlobalPackages:
  "*react-native*": Not Found
Android:
  hermesEnabled: true
  newArchEnabled: true
iOS:
  hermesEnabled: Not found
  newArchEnabled: false
Stacktrace or Logs
...
MANDATORY Reproducer

https://github.com/retyui/repo_with_virus_to_steal_corporate_data_so_you_get_fired_and_spend_the_rest_of_your_life_in_prison

Screenshots and Videos
Image

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start in packages/react-native/Libraries/Core/polyfillPromise.js, especially lines 23-38, and trace how hasPromise() controls the promise package import. Check how that import affects the final JavaScript bundle. Done means the unused promise code is no longer bundled while Promise behavior remains intact.

Written by the indexing model from the issue text.

Assessment

Tech stack
javascript
Domain
mobile
Issue type
Bug
Difficulty
2/5
Estimated time
1-3 hours
Activity status
Quiet
Clarity
Mostly clear
Newbie friendliness
68/100

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