Platform not detected correctly on Android (Platform.OS)

Description

The issue is simple, Platform is not detecting Android correctly in some instances. I am only ever able to reproduce the issue when I save my App.js file and React Native reloads the app. This is causing the OneSignal SDK package that also uses Platform to fall into an iOS-only code path (here).

React Native version:

System:
    OS: macOS 10.15.5
    CPU: (8) x64 Intel(R) Core(TM) i7-7820HQ CPU @ 2.90GHz
    Memory: 87.29 MB / 16.00 GB
    Shell: 5.7.1 - /bin/zsh
  Binaries:
    Node: 12.18.0 - /usr/local/bin/node
    Yarn: 1.12.3 - /usr/local/bin/yarn
    npm: 6.14.4 - /usr/local/bin/npm
    Watchman: Not Found
  Managers:
    CocoaPods: 1.8.4 - /usr/local/bin/pod
  SDKs:
    iOS SDK:
      Platforms: iOS 14.0, DriverKit 19.0, macOS 10.15, tvOS 14.0, watchOS 7.0
    Android SDK:
      API Levels: 24, 26, 27, 28, 29
      Build Tools: 26.0.2, 27.0.3, 28.0.3, 29.0.0, 29.0.2
      System Images: android-23 | Google APIs Intel x86 Atom, android-27 | Google Play Intel x86 Atom, android-28 | Google Play Intel x86 Atom
      Android NDK: Not Found
  IDEs:
    Android Studio: 4.0 AI-193.6911.18.40.6626763
    Xcode: 12.0.1/12A7300 - /usr/bin/xcodebuild
  Languages:
    Java: 1.8.0_191 - /usr/bin/javac
    Python: 2.7.16 - /usr/bin/python
  npmPackages:
    @react-native-community/cli: Not Found
    react: 16.9.0 => 16.9.0 
    react-native: ^0.63.3 => 0.63.3 
    react-native-macos: Not Found
  npmGlobalPackages:
    *react-native*: Not Found

Steps To Reproduce

1. Clone project

git clone https://github.com/OneSignal/react-native-onesignal.git
cd react-native-onesignal/examples/RNOneSignal
git checkout react-native-issue-repro
yarn install

1. Open the android directory with Android Studio and fix any build issues like signing config keystore , gradle, etc…

2. react-native run-android

3. Send yourself a notification by tapping the button “Post a Notification”

4. Open App.js, on line 401 try playing with the 3rd argument. Change the line to OneSignal.postNotification({en:"Testing this post"}, {data:"data"}, state.userId); (i.e. remove the brackets from the last argument).

Somehow I can consistently reproduce the issue by doing that (send notif, remove brackets, save).

Expected Results

I expect the log not to print that the platform is iOS, since I am running this on Android.

Snack, code example, screenshot, or link to a repository:

See line 394 in App.js from the repository.

import { Platform } from 'react-native';
if (Platform.OS === 'ios') console.log("Platform is iOS");

SCREENSHOTS

[Svarto]

Just an update from my side, this was my user error. I found an instance in my app where I had accidentally tried to assign Platform.OS a value (I.e. Platform.OS = “ios”). This broke the Platform module and it never recovered until a restart.

[Svarto]

similar problem, but my Platform.OS resolves to “false”. This breaks linkages to native components and crashes the app. e.g.

Invariant Violation: requireNativeComponent: "RCTSwitch" was not found in the UIManager.

Any idea how to fix this?