null properties in maps stripped away on iOS when sent via TurboModules

@mikehardy

Description

Hello - I'm a maintainer of React Native Firebase (RNFB). RNFB is currently upgrading its packages to TurboModules, and we found a discrepancy between iOS and android that was not previously an issue with NativeModules.

Here is the reproducer: https://github.com/russellwheatley/null-ios-bug

It's pretty simple; run the app on android/iOS. Press the button that appears, it will send this map to native, native will return the exact data back to the JS side:

{ data: { message: 'Hello, world!', nullType: null } }

android will faithfully return the same map, iOS will strip out the property nullType which you can see in DevTools.

This is a rather big departure from NativeModules and will cause problems for a number of RNFB packages like functions, firestore & real-time database.

This issue has been brought up before:
#49291
reactwg/react-native-releases#785

Let me know if you need any further information.

cc. @mikehardy

Steps to reproduce

clone repo: https://github.com/russellwheatley/null-ios-bug
run cd ReproducerApp.
run yarn
follow instructions in README to run app: https://github.com/russellwheatley/null-ios-bug#step-1-start-the-metro-server
press button that appears, and view log in DevTools.
iOS strips out property nullType because it has null value, android does not.

React Native Version

0.80.1

Affected Platforms

Runtime - iOS

Areas

TurboModule - The New Native Module System

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

System:
  OS: macOS 15.5
  CPU: (10) arm64 Apple M1 Max
  Memory: 127.64 MB / 32.00 GB
  Shell:
    version: "5.9"
    path: /bin/zsh
Binaries:
  Node:
    version: 22.15.0
    path: ~/.nvm/versions/node/v22.15.0/bin/node
  Yarn:
    version: 1.22.22
    path: /opt/homebrew/bin/yarn
  npm:
    version: 10.9.2
    path: ~/.nvm/versions/node/v22.15.0/bin/npm
  Watchman:
    version: 2024.12.02.00
    path: /opt/homebrew/bin/watchman
Managers:
  CocoaPods:
    version: 1.15.2
    path: /usr/local/bin/pod
SDKs:
  iOS SDK:
    Platforms:
      - DriverKit 24.5
      - iOS 18.5
      - macOS 15.5
      - tvOS 18.5
      - visionOS 2.5
      - watchOS 11.5
  Android SDK:
    API Levels:
      - "26"
      - "28"
      - "29"
      - "30"
      - "31"
      - "32"
      - "33"
      - "34"
      - "35"
    Build Tools:
      - 28.0.3
      - 29.0.2
      - 29.0.3
      - 30.0.2
      - 30.0.3
      - 33.0.0
      - 33.0.1
      - 34.0.0
      - 35.0.0
    System Images:
      - android-28 | Google APIs Intel x86 Atom
      - android-28 | Google Play Intel x86 Atom
      - android-28 | Google Play Intel x86 Atom_64
      - android-29 | Intel x86 Atom_64
      - android-29 | Google APIs ARM 64 v8a
      - android-30 | Google APIs Intel x86 Atom
      - android-30 | Google Play Intel x86 Atom
      - android-32 | Google Play ARM 64 v8a
      - android-33 | Google APIs ARM 64 v8a
      - android-33 | Google APIs Intel x86 Atom_64
      - android-33 | Google Play ARM 64 v8a
      - android-33 | Google Play Intel x86 Atom_64
      - android-TiramisuPrivacySandbox | Google Play Intel x86 Atom_64
    Android NDK: 22.1.7171670
IDEs:
  Android Studio: 2024.3 AI-243.25659.59.2432.13423653
  Xcode:
    version: 16.4/16F6
    path: /usr/bin/xcodebuild
Languages:
  Java:
    version: 17.0.7
    path: /usr/bin/javac
  Ruby:
    version: 2.6.10
    path: /usr/bin/ruby
npmPackages:
  "@react-native-community/cli":
    installed: 19.0.0
    wanted: 19.0.0
  react:
    installed: 19.1.0
    wanted: 19.1.0
  react-native:
    installed: 0.80.1
    wanted: 0.80.1
  react-native-macos: Not Found
npmGlobalPackages:
  "*react-native*": Not Found
Android:
  hermesEnabled: true
  newArchEnabled: true
iOS:
  hermesEnabled: true
  newArchEnabled: true

Stacktrace or Logs

Android log:

{ data: { message: 'Hello, world!', nullType: null } }


iOS log:

{ data: { message: 'Hello, world!' } }

MANDATORY Reproducer

https://github.com/russellwheatley/null-ios-bug

Screenshots and Videos

No response

@russellwheatley

Hi @russellwheatley, thanks for the issue.
This should be fixed in 0.81 with this commit: 4a4fd1c

Do you mind try to create an app with npx @react-native-community/cli init MyApp --version next --skip-install which uses the RC from 0.81.0, and double check whether the problem is fixed?

@cipolleschi

Hey @cipolleschi - I copy/pasted the dependencies from running the below command into my repro:

npx @react-native-community/cli init MyApp --version next --skip-install

and it was the same result. I even cloned the repo fresh: https://github.com/russellwheatley/null-ios-bug to ensure it wasn't a stale build but it didn't make a difference.

@russellwheatley

@russellwheatley so, the bug was effectively addressed by this PR: #51103

The fix is behind a feature flag, which we turned on but we had to turn off because it was causing a lot of failures internally. People and users might ended up depending on this new behavior and changing it now could be a big breaking change for our users. We need further discussions internally to understand how to roll this out.

One of the benefits of the New Architecture and Codegen is type safety: in general, you should avoid the usage of unknown types and users should always know which are the keys involved. When this is not possible, when the users can specify custom fields, I suggest to use the Object approach that will be converted to an NSDictionary. In that way you can iterate over the keys and check for their presence.

  httpsCallable(
    name: string,
    data: Object ,
  ): Promise<{ data: ResponseData }>;

@cipolleschi

@cipolleschi - could you expand on that, please?

I've tried your method of using Object but it still doesn't have the null key here: https://github.com/russellwheatley/null-ios-bug/blob/main/ReproducerApp/ios/NativeFunctionsModule/RCTNativeFunctionsModule.mm#L21

To be super clear - I have called data.data() and looked for the null (nil key) which is not present. I'm not sure if this is what you meant when you said "iterate over the keys". See below code snippet:

- (void)httpsCallable:(nonnull NSString *)name data:(JS::NativeFunctionsModule::SpecHttpsCallableData &)data resolve:(nonnull RCTPromiseResolveBlock)resolve reject:(nonnull RCTPromiseRejectBlock)reject { 
  	// iterate over `updatedData` or somewhere else?
	id updatedData = data.data();
}

@cipolleschi

@cipolleschi - anything further on this? It's a pretty big problem for RNFB, and we'll have to hack something together to keep parity between android and iOS when we migrate to TurboModules.

This issue is stale because it has been open 180 days with no activity. Remove stale label or comment or this will be closed in 7 days.

This issue is stale because it has been open for 180 days with no activity. It will be closed in 7 days unless you comment on it or remove the "Stale" label.

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`null` properties in maps stripped away on iOS when sent via TurboModules #52802

Description

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

Stacktrace or Logs

MANDATORY Reproducer

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null properties in maps stripped away on iOS when sent via TurboModules #52802

Description

Description

Steps to reproduce

React Native Version

Affected Platforms

Areas

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

Stacktrace or Logs

MANDATORY Reproducer

Screenshots and Videos

Activity

cipolleschi commented on Jul 24, 2025

russellwheatley commented on Jul 25, 2025

cipolleschi commented on Jul 31, 2025

russellwheatley commented on Aug 4, 2025

russellwheatley commented on Sep 2, 2025

react-native-bot commented on Mar 2, 2026

react-native-bot commented on Mar 2, 2026

react-native-bot commented on Aug 30, 2026

react-native-bot commented on Sep 6, 2026

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`null` properties in maps stripped away on iOS when sent via TurboModules #52802

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