try! Swift macros

Recap of WWDC23 Mercari
https://mercari.connpass.com/event/285179/

Appendix
https://gist.github.com/tkhs0604/d2b6b1a84eeb3bead6faa6a6a1e6af33

Transcript

1. try! Swift macros Recap of WWDC23 Mercari https://mercari.connpass.com/event/285179/
2. About me • Nickname ◦ kenken • Company ◦ Merpay, Inc. (since May, 2021) • Occupation ◦ Software Engineer, Android (and iOS at some of my previous companies) • Accounts ◦ Twitter: @tkhs0604 ◦ GitHub: @tkhs0604 ◦ Bluesky: @kenken.bsky.social • Other ◦ DroidKaigi community staff
3. What made me interested in Swift macros?
4. Twitter 🐤 https://twitter.com/ailtonvivaz/status/1666922079294201857
5. Comparison between Swift and Kotlin codes • Swift code with SwiftRequest (https://github.com/ailtonvivaz/swift-request) • Kotlin code with Retrofit (https://github.com/square/retrofit)
6. 😳
7. Agenda • What is Swift macros • Freestanding macros and Attached macros • How to implement macros
8. try! したけど難しかった Swift macros Recap of WWDC23 Mercari https://mercari.connpass.com/event/285179/
9. What is Swift macros
10. Swift macros • A feature added from Swift 5.9 ◦ You can use it after Xcode 15.0 beta • A tool for generating boilerplate codes repetitively written by hand • #Preview, @Observable etc. are created with Swift macros Cited from: https://docs.swift.org/swift-book/documentation/the-swift-programming-language/macros/
11. Swift macros • Transforms the syntax tree of a source code at compile time ◦ Input code to a macro and output code of macro expansion are validated syntactically ◦ Values passed to a macro and in the code generated by a macro are type-checked ◦ If the implementation of a macro has any error, Swift compiler treats it as a compilation error Cited from: https://developer.apple.com/videos/play/wwdc2023/10167/?time=291
12. How to give Swift macros a try • File > New > Package…
13. Package structure Declaration of a macro Implementation of a macro Test of a macro
14. Freestanding macros and Attached macros
15. Role in the context of Swift macros Cited from: https://developer.apple.com/videos/play/wwdc2023/10167?time=383
16. Available macro roles Cited from: https://developer.apple.com/videos/play/wwdc2023/10167?time=403 • Freestanding macros: Can be used independently • Attached macros: Can be used with some declaration
17. Use case of @freestanding(expression) Cited from: https://developer.apple.com/videos/play/wwdc2023/10167/?time=483
18. • 2 dimensional array Use case of @freestanding(declaration) Cited from: https://developer.apple.com/videos/play/wwdc2023/10167/?time=593 • 3 dimensional array
19. Use case of @freestanding(declaration) Cited from: https://developer.apple.com/videos/play/wwdc2023/10167/?time=593
20. Use case of @attached(peer) Cited from: https://developer.apple.com/videos/play/wwdc2023/10167/?time=658
21. Use case of @attached(accessor) Cited from: https://developer.apple.com/videos/play/wwdc2023/10167/?time=735
22. Use case of @attached(memberAttribute) Cited from: https://developer.apple.com/videos/play/wwdc2023/10167/?time=822 Role composition
23. Use case of @attached(memberAttribute) Cited from: https://developer.apple.com/videos/play/wwdc2023/10167/?time=822 Role composition
24. Use case of @attached(member) Cited from: https://developer.apple.com/videos/play/wwdc2023/10167/?time=930
25. Use case of @attached(conformance) Cited from: https://developer.apple.com/videos/play/wwdc2023/10167/?time=1011
26. In the end…
27. How to implement macros
28. Package structure (Repeated) Declaration of a macro Implementation of a macro Test of a macro
29. #externalMacro • Specifies the plug-in (module) which the compiler should launch and the name of a type inside the plug-in • When Swift expands the following macro, #stringify(_:) will launch a plug-in called "MyLibMacros" and ask a type called "StringifyMacro" to expand it Cited from: https://developer.apple.com/videos/play/wwdc2023/10167/?time=1102
30. Macro role protocols • Used to create a macro implementation ◦ https://github.com/apple/swift-syntax/tree/main/Sources/SwiftSyntaxMacros/MacroProtocols Cited from: https://developer.apple.com/videos/play/wwdc2023/10167/?time=1356
31. Abstract syntax tree (AST) • A tree representation of the abstract syntactic structure of a source code • SwiftSyntax is a library that helps us parse, inspect, manipulate, and generate Swift source code ◦ https://github.com/apple/swift-syntax Cited from: https://developer.apple.com/videos/play/wwdc2023/10167/?time=1288
32. Swift AST Explorer • A tool for visualizing AST ◦ https://swift-ast-explorer.com/
33. Sample of a macro implementation • Implemented as an extension in this example ◦ https://github.com/DougGregor/swift-macro-examples/blob/main/MacroExamplesPlugin/Dictio naryIndirectionMacro.swift#L63-L84
34. 😇
35. Summary • Swift macros is a tool for generating boilerplate codes • Inputs and outputs are syntax-checked and type-checked at compile time • Some useful macros, like #preview and @Observable have already been introduced • SwiftSyntax is an essential tool for implementing macros ◦ Quite difficult to understand… 😇 • So… let’s try to create macros by yourself and share knowledges!
36. Thank you
37. Appendix • GitHub Gist ◦ https://gist.github.com/tkhs0604/d2b6b1a84eeb3bead6faa6a6a1e6af33