Generate @resultbuilder with SwiftSyntaxBuilder

[kimdv]

Depends on

• Fix indent when there is a leading new line #480
• Port SyntaxBuildableWrappers to Swift #485

This is still WIP, and there is still some way to go!

With gyb

@resultBuilder
public struct CodeBlockItemListBuilder {

  /// The type of individual statement expressions in the transformed function,
  /// which defaults to Component if buildExpression() is not provided.
  public typealias Expression = ExpressibleAsCodeBlockItem

  /// The type of a partial result, which will be carried through all of the
  /// build methods.
  public typealias Component = [ExpressibleAsCodeBlockItem]

  /// The type of the final returned result, which defaults to Component if
  /// buildFinalResult() is not provided.
  public typealias FinalResult = CodeBlockItemList

  /// Required by every result builder to build combined results from
  /// statement blocks.
  public static func buildBlock(_ components: Component...) -> Component {
    return components.flatMap { $0 }
  }

  /// If declared, provides contextual type information for statement
  /// expressions to translate them into partial results.
  public static func buildExpression(_ expression: Expression) -> Component {
    return [expression]
  }
  
  /// Add all the elements of `expression` to this result builder, effectively flattening them.
  public static func buildExpression(_ expression: ExpressibleAsCodeBlockItemList) -> Component {
    return expression.createCodeBlockItemList().elements
  }
  
  /// Enables support for `if` statements that do not have an `else`.
  public static func buildOptional(_ component: Component?) -> Component {
    return component ?? []
  }

  /// With buildEither(second:), enables support for 'if-else' and 'switch'
  /// statements by folding conditional results into a single result.
  public static func buildEither(first component: Component) -> Component {
    return component
  }

  /// With buildEither(first:), enables support for 'if-else' and 'switch'
  /// statements by folding conditional results into a single result.
  public static func buildEither(second component: Component) -> Component {
    return component
  }

  /// Enables support for 'for..in' loops by combining the
  /// results of all iterations into a single result.
  public static func buildArray(_ components: [Component]) -> Component {
    return components.flatMap { $0 }
  }

  /// If declared, this will be called on the partial result of an 'if
  /// #available' block to allow the result builder to erase type
  /// information.
  public static func buildLimitedAvailability(_ component: Component) -> Component {
    return component
  }

  /// If declared, this will be called on the partial result from the outermost
  /// block statement to produce the final returned result.
  public static func buildFinalResult(_ component: Component) -> FinalResult {
    return .init(component.map { $0.createCodeBlockItem() })
  }
}

With SwiftSyntaxBuilderGeneration

@resultBuilder
public struct CodeBlockItemListBuilder{
  
/// Required by every result builder to build combined results from
/// statement blocks.
public static func buildBlock(_ components: Component...)-> Component{
    return components.flatMap()
  }
  
/// If declared, provides contextual type information for statement
/// expressions to translate them into partial results.
public static func buildExpression(_ expression: Expression)-> Component{
    return [expression]
  }
  
/// Add all the elements of `expression` to this result builder, effectively flattening them.
public static func buildExpression(_ expression: ExpressibleAsCodeBlockItemList)-> Component{
    return components.flatMap()
  }
  
/// Enables support for `if` statements that do not have an `else`.
public static func buildOptional(_ component: Component?)-> Component{
    return component??[]
  }
  
/// With buildEither(second:), enables support for 'if-else' and 'switch'
/// statements by folding conditional results into a single result.
public static func buildEither(firstcomponent: Component)-> Component{
    return component
  }
  
/// With buildEither(first:), enables support for 'if-else' and 'switch'
/// statements by folding conditional results into a single result.
public static func buildEither(secondcomponent: Component)-> Component{
    return component
  }
  
/// Enables support for 'for..in' loops by combining the
/// results of all iterations into a single result.
public static func buildArray(_ components: [Component])-> Component{
    return .component
  }
  
/// If declared, this will be called on the partial result of an 'if'
/// #available' block to allow the result builder to erase type
/// information.
public static func buildLimitedAvailability(_ component: Component)-> Component{
    return component
  }
  
/// If declared, this will be called on the partial result from the outermost
/// block statement to produce the final returned result.
public static func buildFinalResult(_ component: Component)-> Component{
  }
}

[fwcd]

A few style nitpicks, but otherwise this looks good! 👍

[kimdv]

Is there a way with the new API to add new lines, without should adding a empty line at the beginning of each Decl

[kimdv]

@swift-ci please test

[fwcd]

Since all of these functions return single expressions, we could omit the return here (and in the other builder functions).

[kimdv]

I had the discussion with @ahoppen at some point.

We decided on going with explicit return, if remember correctly.

Not sure if that opinion have changed?

[ahoppen]

I have a general preference for explicit return, but that might be personal. I gave up actively fighting against implicit returns 😆

[kimdv]

Personally I also like returns in methods as it read better IMO 😬

[fwcd]

.newlines(1) be shortened to .newline IIRC

[kimdv]

I think it's on Trivia

At least I get Type 'TriviaPiece' has no member 'newline'

[ahoppen]

Wohoo. This was so easy to review.

[ahoppen]

@swift-ci Please test

[kimdv]

@swift-ci please test