Emit immediately by default

I don’t agree with the current false default value for emitImmediately. I would argue most idiomatic reactive code using FlowBinding will want the initial value. In addition, RxBinding emits the initial value by default, and FlowBinding clearly advertises itself as its direct counterpart.

Obviously this is a behavior breaking change, but an important one to get right early.

[svenjacobs]

What about making emitImmediately = true the default and remove that parameter and distinguish between an initial-value flow with InitialValueFlow and a non initial-value flow with Flow as usual.

Implementation of InitialValueFlow could look like this

class InitialValueFlow<T>(private val flow: Flow<T>) : Flow<T> by flow {

    fun skipInitialValue(): Flow<T> = flow.drop(1)
}

or as an inline class

inline class InitialValueFlow<T>(private val flow: Flow<T>) : Flow<T> {

    fun skipInitialValue(): Flow<T> = flow.drop(1)

    @InternalCoroutinesApi
    override suspend fun collect(collector: FlowCollector<T>) = flow.collect(collector)
}

I still think representing that different behaviour through the type system is better than having a boolean parameter.

[chris-horner]

Having the flow emit immediately by default feels more natural to me too.

Thinking on it a bit, I agree that @svenjacobs’s approach is probably the best bet. I always appreciated the explicit skipInitialValue() in RxBinding, and providing this behaviour through a type rather than a parameter reads a little nicer.

Thumbs up from me 👍