[RFC] Swift Macro support for Node boilerplate

[amyworrall]

[RFC] Swift Macro support for Node boilerplate

[amyworrall]

I'd like to get people's feedback on this! Obviously we can't land it until Xcode 15 is out of beta, but this can be a taste of things to come.

What I've done here is generated all the boilerplate for node initialisation, cloning, encoding, property access etc using a Swift macro. You might use it like this:

public enum ListType: String, Codable {
  case bullet
  case number
  case check
}

extension NodeType {
  public static let list = NodeType(rawValue: "list")
}

@LexicalNode(.list)
public class ListNode: ElementNode {
  private var _listType: ListType = .bullet
  private var _start: Int = 1
}

and the macro would fill in all the extra boilerplate that you would usually have to write yourself, like so:

open override class var type: NodeType {
  .list
}

enum CodingKeys: String, CodingKey {
    case listType
    case start

}

public convenience init(listType: ListType , start: Int ) {
  self.init(listType: listType, start: start, key: nil)
}

public required init(listType: ListType , start: Int , key: NodeKey?) {
  self._listType = listType
  self._start = start

  super.init(key)
}

override public func clone() -> Self {
  Self (listType: _listType, start: _start, key: key)
}

override public func encode(to encoder: Encoder) throws {
  try super.encode(to: encoder)
  var container = encoder.container(keyedBy: CodingKeys.self)
  try container.encode(_listType, forKey: .listType)
  try container.encode(_start, forKey: .start)

}

public required init(from decoder: Decoder) throws {
  let container = try decoder.container(keyedBy: CodingKeys.self)
  self._listType = try container.decode(ListType .self, forKey: .listType)
  self._start = try container.decode(Int .self, forKey: .start)

  try super.init(from: decoder)
}

public var listType: ListType  {
  return getLatest()._listType
}

public func getListType() -> ListType  {
  return getLatest()._listType
}

public func setListType(_ val: ListType ) throws {
  try getWritable()._listType = val
}

public var start: Int  {
  return getLatest()._start
}

public func getStart() -> Int  {
  return getLatest()._start
}

public func setStart(_ val: Int ) throws {
  try getWritable()._start = val
}

I think you'll agree this is a lot easier!

It won't be compulsory to write Lexical nodes in this way. If you need more control, you can still write nodes by implementing these methods manually.

At the moment, the macro doesn't allow much customisation of the behaviour. It's all or nothing -- for example, you can't implement your own encode method but have the macro do everything else. I'd like to improve this in the future, making the macro ignore methods that have already been written manually.

[iBenjamin]

@amyworrall Xcode 15 is released can this pr be merged?

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