IssueTracker

Definitely want to support this. Currently investigating moving the Callbacks to interfaces so that wrapping/conversion can be done:

    private abstract class WrapperDataSource<in A, B>(private val source: PositionalDataSource<A>)
            : PositionalDataSource<B>() {
        override fun loadInitial(params: LoadInitialParams, callback: LoadInitialCallback<B>) {
            source.loadInitial(params, object: LoadInitialCallback<A> {
                override fun onResult(data: List<A>, position: Int, totalCount: Int) {
                    callback.onResult(convert(data), position, totalCount)
                }

                override fun onResult(data: List<A>, position: Int) {
                    callback.onResult(convert(data), position)
                }
            })
        }

        override fun loadRange(params: LoadRangeParams, callback: LoadRangeCallback<B>) {
            source.loadRange(params) { data -> callback.onResult(convert(data)) }
        }

        protected abstract fun convert(source: List<A>): List<B>
    }

Making them interfaces makes it easy to wrap/test. Downside is that external callers can't use some of the guts of the callback impl (like validating non-negative positions), but this should make it much more reasonable to wrap, decorate, or otherwise post-process data loaded from e.g. Room. In the network case, the equivalent might be post-processing a network request in a way that's awkward to inject into network loading code.

Fixed internally by making Params constructors public, and Callbacks abstract. Will go out with next alpha release.

We're also investigating making it easier to wrap and do decoration/type conversions, since the example in #2 mostly works, but is incomplete - it needs to handle invalidates.

Released: https://developer.android.com/topic/libraries/architecture/release-notes.html#paging

I don't think there is really any workaround.  We're working on getting alpha03 out soon though.  Thanks!