[akka-stream] Concatenate multiple Sources while preserving materialized values

[Arron Norwell]

Hi,

I'm looking for a good way to concatenate sources while preserving materialized values. For example, If I have 

val source1: Source[T,Mat] = _
val source2: Source[T,akka.NotUsed] = _

I would like to be able to preserve the first materialized value (and possibly more generally, support other means of combination), e.g.:

val concatSource: Source[T, Mat] = Source.combine(source1, source2)(Concat[T]())

It seems difficult to get this to work, because concat discards materialized values. Is there a good way to approach this?

[Arron Norwell]

Sorry, this is actually supported and very straightforward. Solution is:

//most common Keep.left case
source1.concat(source2)

//more general
source1.concatMat(source2)(Keep.both) //or whatever strategy