React Native's Native Modules are great, but their documentation is a little...lacking.
Let's talk about the UserInfo field when we reject a promise in a Native Module.
According to the docs (for both Android and iOS), RN Native Module promises can be rejected with various combinations of the following parameters:
String code, String message, WritableMap userInfo, Throwable throwable
That's great! Except we never quite get where to find userInfo. After some poking
around, I found that you can access userInfo from the error object caught
on a promise rejection.
import {NativeModules} from 'react-native'
const {SomeModule} = NativeModules
...
try {
await SomeModule.doSomething()
} catch (error) {
error.userInfo
}
Simple, so it's very strange this is just not documented anywhere.