Please include `index.js.flow` in the npm package

[buschco]

Description

There are still people using react-native with flow and at some point the types went to any in my project. Today I figured out adding the index.js.flow file (https://github.com/facebook/react-native/blob/v0.79.3/packages/react-native/index.js.flow) manually to the react-native node module the typings worked again.

Am I missing something?

Steps to reproduce

1. Setup a react-native project with flow (or clone https://github.com/buschco/react-native-flow + cd ReproducerApp && npm i)

2. import {Alert} from 'react-native' -> Alert has type any

3. add index.js.flow File (https://github.com/facebook/react-native/blob/v0.79.3/packages/react-native/index.js.flow) to node_modules/react-native/index.js.flow -> Alert no longer any

React Native Version

0.79.3

Affected Platforms

Build - MacOS

Output of npx @react-native-community/cli info

info Fetching system and libraries information...
System:
  OS: macOS 15.5
  CPU: (14) arm64 Apple M4 Pro
  Memory: 412.52 MB / 48.00 GB
  Shell:
    version: "5.9"
    path: /bin/zsh
Binaries:
  Node:
    version: 18.20.5
    path: ~/.nvm/versions/node/v18.20.5/bin/node
  Yarn:
    version: 1.22.22
    path: ~/.nvm/versions/node/v18.20.5/bin/yarn
  npm:
    version: 10.8.2
    path: ~/.nvm/versions/node/v18.20.5/bin/npm
  Watchman: Not Found
Managers:
  CocoaPods:
    version: 1.16.2
    path: /Users/colin/.rbenv/shims/pod
SDKs:
  iOS SDK:
    Platforms:
      - DriverKit 24.2
      - iOS 18.2
      - macOS 15.2
      - tvOS 18.2
      - visionOS 2.2
      - watchOS 11.2
  Android SDK: Not Found
IDEs:
  Android Studio: 2024.2 AI-242.23339.11.2421.12550806
  Xcode:
    version: 16.2/16C5032a
    path: /usr/bin/xcodebuild
Languages:
  Java:
    version: 21.0.3
    path: /Users/colin/.sdkman/candidates/java/current/bin/javac
  Ruby:
    version: 3.3.6
    path: /Users/colin/.rbenv/shims/ruby
npmPackages:
  "@react-native-community/cli":
    installed: 18.0.0
    wanted: 18.0.0
  react:
    installed: 19.0.0
    wanted: 19.0.0
  react-native:
    installed: 0.79.3
    wanted: 0.79.3
  react-native-macos: Not Found
npmGlobalPackages:
  "*react-native*": Not Found
Android:
  hermesEnabled: true
  newArchEnabled: true
iOS:
  hermesEnabled: Not found
  newArchEnabled: false

Stacktrace or Logs

yarn flow type-at-pos alert.js 2 10
yarn run v1.22.22
$ /<...>/node_modules/.bin/flow type-at-pos test.js 2 10
any (implicit)

MANDATORY Reproducer

https://github.com/react-native-community/reproducer-react-native (the reproducer is not typed in flow)

Screenshots and Videos

No response

[react-native-bot]

Warning

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:

• For majority of bugs: send us a Pull Request with the RNTesterPlayground.js edited to reproduce your bug.
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• If your bug is build/upgrade related: a project using our Reproducer Template

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[cortinico]

cc @huntie as per your recent changes

[huntie]

@buschco Hey! Just echoing what I've commented on #51886 (which we will merge ✅).

FYI: We haven't been considering our open source support for React Native + Flow as supported for a couple of years 😅

• This does mean that on upgrading to 0.79 and 0.80, we made quite a lot of internal type changes — including the new index.js.flow entry point, but also many changes to our Flow type shapes to align better with TypeScript/source. So, you'll need to keep up with these and there were several breaking changes 🙏🏻
• Do consider migrating projects to TypeScript for long term support.

See also #51556 recently.

[buschco]

Thanks for the follow up!

Really sad to hear, I really liked flow!

[huntie]

@buschco We like Flow too!

To be honest, the React Native codebase will be very well typed in Flow so long as we're using it in Meta's codebase (the foreseeable future 💯).

Maybe what I'm referring to is we're not considering Flow support for open source users as a strong concern, e.g. not considering as breaking changes in releases, not providing our dependency typedefs. But it'll certainly be possible (if projects are stubborn enough!) to consume react-native via Flow for a while yet.