Result builders versus private types

David_Catmull · November 4, 2022, 10:03pm

I'm working on a result builder, and running into a problem where I'm having to make some of my implementation details public. Since a result builder essentially transforms the code in place, all types involved (eg those used to hold intermediate results) must be made public even if they're supposed to be implementation details and not used outside the result builder.

Anyone else run into this? Have you found any good ways to deal with it?

stephencelis · November 4, 2022, 11:25pm

We use some in 5.7 where possible to hide the type, and otherwise underscore the public name to keep Xcode from documenting/autocompleting it.

github.com

pointfreeco/swift-composable-architecture/blob/b21a7d5aadd7c6ee4cc5bcf6771fcbf32d6b1bcc/Sources/ComposableArchitecture/Reducer/ReducerBuilder.swift

/// A result builder for combining reducers into a single reducer by running each, one after the
/// other, and returning their merged effects.
///
/// It is most common to encounter a reducer builder context when conforming a type to
/// ``ReducerProtocol`` and implementing its ``ReducerProtocol/body-swift.property-97ymy`` property.
///
/// See ``CombineReducers`` for an entry point into a reducer builder context.
@resultBuilder
public enum ReducerBuilder<State, Action> {
  #if swift(>=5.7)
    @inlinable
    public static func buildArray(
      _ reducers: [some ReducerProtocol<State, Action>]
    ) -> some ReducerProtocol<State, Action> {
      _SequenceMany(reducers: reducers)
    }

    @inlinable
    public static func buildBlock() -> some ReducerProtocol<State, Action> {
      EmptyReducer()

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