🔥 update() with null does not remove the value from Firebase Database in iOS

[Stas-Buzunko]

Issue

"@react-native-firebase/database": "^21.4.0"

import { firebase } from '@react-native-firebase/database'

firebase
    .database()
    .ref()
    .update({
      'any-path': null
    })
    .then(() => {
      console.log('Update succeeded')
    })
    .catch((error) => {
      console.error('Update failed: ', error);
    });

On iOS, using null with the update() method doesn't remove the key's value from the database as expected; instead, the old value remains. However, on Android, Web, and Admin SDK, this behavior works as intended, and the key is removed.

Updating the value to false works as expected, and the value gets updated correctly in the database.

I face the issue every time on the iOS simulator (v18.1, Xcode 16), but there were also cases in production with the older version of @react-native-firebase/database: ^18.3.2. I believe that not all iOS production users are affected; otherwise, the issue would have been noticed earlier.

Describe your issue here

---

Project Files

Javascript

Click To Expand

package.json:

# N/A

firebase.json for react-native-firebase v6:

# N/A

iOS

Click To Expand

ios/Podfile:

• I'm not using Pods
• I'm using Pods and my Podfile looks like:

# N/A

AppDelegate.m:

// N/A

---

Android

Click To Expand

Have you converted to AndroidX?

• my application is an AndroidX application?
• I am using android/gradle.settings jetifier=true for Android compatibility?
• I am using the NPM package jetifier for react-native compatibility?

android/build.gradle:

// N/A

android/app/build.gradle:

// N/A

android/settings.gradle:

// N/A

MainApplication.java:

// N/A

AndroidManifest.xml:

<!-- N/A -->

---

Environment

Click To Expand

react-native info output:

 OUTPUT GOES HERE

• Platform that you're experiencing the issue on:
  • iOS
  • Android
  • iOS but have not tested behavior on Android
  • Android but have not tested behavior on iOS
  • Both
• react-native-firebase version you're using that has this issue:
  • 18.3.2-21.4.0
• Firebase module(s) you're using that has the issue:
  • Database
• Are you using TypeScript?
  • Y & ^5.0.4

---

• 👉 Check out React Native Firebase and Invertase on Twitter for updates on the library.

[Stas-Buzunko]

firebase
    .database()
    .ref('some-path')
    .update({ someKey: null }); // Doesn't work as expected

firebase
    .database()
    .ref('some-path/someKey')
    .set(null); // Works fine

[russellwheatley]

Hey @Stas-Buzunko - I just wrote a test for this use case and it passed across all platforms: #8146

Also tested locally and it worked. Not sure why it doesn't work for you, it is strange. I had a look at JS code/iOS code and we do nothing to null value properties.

I did notice in your first example, it is executing on the parent node, not sure if that makes a difference but something to double check.

[Stas-Buzunko]

hi @russellwheatley

1. This is a narrow issue. We've had ~1500 new users in the last 2 months, with 70% on iOS (~1050), and only 9 (0.85%) faced the problem.

2. We validated this by creating a Firebase function that logged those 9 affected users.

Now, another developer and I can reproduce the issue (different machines) on iOS simulator 18.1 (Version 16.0 (1038), SimulatorKit 942, CoreSimulator 987.2, Xcode 16.1). I believe it’s related to the iOS version, not RN Firebase or Firebase iOS SDK; otherwise, more users would be impacted.

What’s concerning is seeing this issue on the latest simulator. The key takeaway is that we can't rely on "null" to delete keys in critical situations. We'll refactor all "null" usages to use set() instead.

[Stas-Buzunko]

I can record a video demonstrating the problem if you'd like, and if it would be helpful.

[mikehardy]

🤔 hmm - what platform are you all on where you reproduce it? Do you reproduce it every time or is there something you have to do to reproduce it reliably?

Our CI (where this test ran, but once and only once) is running:

• /Library/Developer/CoreSimulator/Volumes/iOS_22B81/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS 18.1.simruntime/
• https://github.com/actions/runner-images/blob/macos-14-arm64/20241022.361/images/macos/macos-14-arm64-Readme.md
• Xcode is set to 16.1.0 (16B40)
• tests running against firebase emulator suite

If we can reliably reproduce this we may be able to fix it but reproduction here seems like it should be the focus first