Codegen and different component props between iOS and Android

[gispada]

When defining Codegen specifications for a Fabric component, what's the best way to deal with different props between platforms?

It seems that every file ending with NativeComponent gets picked out by Codegen, am I right? So it might generate code for props that will never be used on both platforms.

Setting jsRootDir in android/build.gradle to a different folder than jsSrcsDir in package.json's codegenConfig can be a valid approach?

[gispada]

Upon further investigation, I found out that it's possible to specify which platform to exclude directly in the codegenNativeComponent function:

export default codegenNativeComponent<NativeProps>('RNComponent', {
  excludedPlatforms: ['android'],
}) as HostComponent<NativeProps>;

Digging into Codegen source code it also seems that — for modules only — it's possible to separate platforms by appending IOS, Android or Cxx to the module filename.

One thing that's not entirely clear is why C++ files in android/build/generated/source/codegen/jni/react/renderer/components/MyComponent contain references to those components that should be excluded. They are indeed excluded from the java generated code (no interface/delegate), but are still appearing in the jni layer.

[cortinico]

Thanks for your investigation @gispada
This is currently not easily doable out of the box. The current solution is either to:

• Have a spec which is a superset of the capabilities of the two platforms, and stub the implementation for platform specific APIs
• Use excludedPlatforms: ['...'] as you suggest. You'll be effectively not generating spec for one of the two platform.
• Use the module filename suffixes as you suggest. This is however not documented and we're probably going to revist this.

Ideally, the codegen should be able to handle .android.js and .ios.js file extensions.

One thing that's not entirely clear is why C++ files in android/build/generated/source/codegen/jni/react/renderer/components/MyComponent contain references to those components that should be excluded

This is a bug to me and should be fixed. Not a major one as you will probably ignore those sources, but still somethign to clean up.