[chrfalch]

Summary:

SwiftPM is planned to become the default iOS setup, with CocoaPods as the opt-out. To be able to accomplish this, we want to keep the current templates with Cocoapods and do the opt-out through the npx react-native spm deinit command - meaning that the cli will:

1. Create a new app from the existing templates
2. Run the `npx react-native spm` command instead of `pod install`
3. This gives us the necessary tools for reverting/going back to Cocoapods through `npx react-native spm deinit`.

For that, an app that was converted to SwiftPM must be able to fully go back to CocoaPods. Today it cannot:

• The conversion (spm add --deintegrate, also run by plain npx react-native spm on a new app) deletes each Podfile line that names a React Native call. A call that spans several lines, such as use_react_native!(…), loses only its first line. The Podfile is then invalid Ruby.
• spm deinit removes SwiftPM from the Xcode project, but it does not touch the Podfile.

This PR makes npx react-native spm deinit the way back to CocoaPods:

1. The conversion renames the Podfile. It runs pod deintegrate, then moves ios/Podfile to ios/Podfile.bak without changes. The line editing is removed.
2. The conversion refuses in two cases, before it changes anything: the Podfile has pods that are not React Native (they would stop working under SwiftPM), or Podfile.bak already exists.
3. spm deinit restores the Podfile from Podfile.bak and prints "Next step: run pod install". If both files exist, it stops and changes nothing.
4. spm deinit undoes the .gitignore lines the conversion wrote. The conversion now records those lines in its marker file (.spm-injected.json), so deinit removes only them. Without a record, .gitignore is not touched.
5. spm deinit removes the ReactNativeSPM folders that are empty after it deletes its files.

The docs in scripts/spm/__docs__ describe the way back. They also say:

• The conversion removes the app target's own REACT_NATIVE_PATH, and deinit does not restore it. pod install sets it again for the whole project, through react_native_post_install. Only a Podfile without that call needs a manual check.
• A SwiftPM app without a Podfile needs @react-native-community/cli 21 or newer. Older versions find the iOS project through the Podfile (see feat: detect Swift Package Manager projects react-native-community/cli#2858).

Changelog:

[IOS] [CHANGED] - react-native spm moves the Podfile to Podfile.bak when it converts an app to SwiftPM, and react-native spm deinit restores it, so an app can go back to CocoaPods.

Test Plan:

Unit tests:

yarn test packages/react-native/scripts/spm/__tests__

23 suites, 1183 tests pass. ESLint, Prettier and Flow are clean on the changed files.

A new app, outside the monorepo, on React Native 0.89.0-nightly-20261021-c7429b0e9 with CLI 21.0.0-alpha.1. The three changed script files were copied into node_modules/react-native/scripts.

1. npx react-native spm converts the app. ios/Podfile.bak is the same as the original Podfile.
2. SwiftPM Debug and Release builds succeed. Release makes main.jsbundle.
3. npx react-native spm deinit restores the Podfile with the same content. It removes the .gitignore it created, the ReactNativeSPM folder and the marker. No SwiftPM entries remain in the Xcode project.
4. cd ios && pod install succeeds.
5. CocoaPods Debug and Release builds succeed. Release makes main.jsbundle, and REACT_NATIVE_PATH resolves to the app's node_modules/react-native.

private/helloworld in the monorepo: the same round trip passed through the CocoaPods Debug build. A second spm add --deintegrate stopped with "Nothing was changed".

Not checked: a CocoaPods Release build of helloworld. My checkout setup made Metro fail while it bundled. The same build works in the new app above.