Metaprogramming with Kotlin Symbol Processing

Transcript

1. Metaprogramming with Kotlin Symbol Processing Anthony Restaino
2. Topics What is Metaprogramming? History of Metaprogramming Kotlin Symbol Processing How-to AI and Metaprogramming
3. Metaprogramming “[A] programming technique in which computer programs have the ability to treat other programs as their data.”
4. Metaprogramming Re fl ective Programming Compile time program execution
5. Ancient History April 1960 - LISP published
6. Less Ancient History April 1960 - LISP published January 1996 - Java 1.0 published
7. Less Ancient History April 1960 - LISP published January 1996 - Java 1.0 published February 2005 - JSR 269 - AP • Annotation Processing (AP) • Generate Java code • Released in Java 6
8. Recent History April 1960 - LISP published January 1996 - Java 1.0 published February 2005 - JSR 269 - AP March 2017 - KAPT • Runs on top of Java AP • Generate Java or Kotlin code • AP compatible
9. Recent History April 1960 - LISP published January 1996 - Java 1.0 published February 2005 - JSR 269 - AP March 2017 - KAPT September 2020 - KSP • Kotlin fi rst code generation • AP and KAPT incompatible
10. Scenario val TAG = "Droidcon" Log.d(TAG, "Hello Droidcon")
11. Solutions Hardcode Re fl ection (Metaprogramming) Code Generation (Metaprogramming)
12. Hardcode val TAG = "Droidcon" Log.d(TAG, "Hello Droidcon")
13. Re fl ection val TAG = Droidcon :: class.simpleName Log.d(TAG, "Hello Droidcon")
14. Code Generation 1. Find classes 2. Generate code 3. Use generated code
15. Our Goal @Tag object Droidcon { fun doLogging() { Log.d(TAG, "Hello Droidcon") } }
16. Our Goal val Droidcon.TAG : String get() = "Droidcon"
17. Setup implementation(project(":tagger")) ksp(project(":tagger - compiler")) Annotation (runtime) module Kotlin symbol processing module App module
18. Annotation annotation class Tag
19. Annotation @Target(AnnotationTarget.CLASS) annotation class Tag
20. Annotation @Retention(AnnotationRetention.SOURCE) @Target(AnnotationTarget.CLASS) annotation class Tag
21. Processor Provider class TaggerSymbolProcessorProvider : SymbolProcessorProvider { }
22. Processor Provider class TaggerSymbolProcessorProvider : SymbolProcessorProvider { override fun create( environment: SymbolProcessorEnvironment ): SymbolProcessor = TaggerSymbolProcessor( environment.codeGenerator ) }
23. Processor Provider class TaggerSymbolProcessorProvider : SymbolProcessorProvider { override fun create( environment: SymbolProcessorEnvironment ): SymbolProcessor = TaggerSymbolProcessor( environment.codeGenerator ) } com.tagger.TaggerSymbolProcessorProvider
24. Processor Provider class TaggerSymbolProcessorProvider : SymbolProcessorProvider { override fun create( environment: SymbolProcessorEnvironment ): SymbolProcessor = TaggerSymbolProcessor( environment.codeGenerator ) } com.tagger.TaggerSymbolProcessorProvider
25. Processor class TaggerSymbolProcessor( private val codeGenerator: CodeGenerator, ) : SymbolProcessor { }
26. class TaggerSymbolProcessor( private val codeGenerator: CodeGenerator, ) : SymbolProcessor { override fun process(resolver: Resolver): List<KSAnnotated> { } } Processor
27. override fun process(resolver: Resolver): List<KSAnnotated> { }
28. override fun process(resolver: Resolver): List<KSAnnotated> { resolver.getSymbolsWithAnnotation(Tag :: class.qualifiedName ! ! ) }
29. override fun process(resolver: Resolver): List<KSAnnotated> { resolver.getSymbolsWithAnnotation(Tag :: class.qualifiedName ! ! ) .filterIsInstance<KSClassDeclaration>() }
30. override fun process(resolver: Resolver): List<KSAnnotated> { resolver.getSymbolsWithAnnotation(Tag :: class.qualifiedName ! ! ) .filterIsInstance<KSClassDeclaration>() .map { declaration -> } }
31. override fun process(resolver: Resolver): List<KSAnnotated> { resolver.getSymbolsWithAnnotation(Tag :: class.qualifiedName ! ! ) .filterIsInstance<KSClassDeclaration>() .map { declaration -> val funSpec = FunSpec .getterBuilder() .addStatement("return %S", "Droidcon") .build() } }
32. override fun process(resolver: Resolver): List<KSAnnotated> { resolver.getSymbolsWithAnnotation(Tag :: class.qualifiedName ! ! ) .filterIsInstance<KSClassDeclaration>() .map { declaration -> val funSpec = FunSpec .getterBuilder() .addStatement("return %S", declaration.simpleName.asString()) .build() } }
33. override fun process(resolver: Resolver): List<KSAnnotated> { resolver.getSymbolsWithAnnotation(Tag :: class.qualifiedName ! ! ) .filterIsInstance<KSClassDeclaration>() .map { declaration -> val funSpec = FunSpec .getterBuilder() .addStatement("return %S", declaration.simpleName.asString()) .build() PropertySpec .builder("TAG", String :: class) .receiver(ClassName("com.droidcon", "Droidcon")) .mutable(false) .getter(funSpec) .addOriginatingKSFile(declaration.containingFile !! ) .build() } }
34. override fun process(resolver: Resolver): List<KSAnnotated> { resolver.getSymbolsWithAnnotation(Tag :: class.qualifiedName ! ! ) .filterIsInstance<KSClassDeclaration>() .map { declaration -> val funSpec = FunSpec .getterBuilder() .addStatement("return %S", declaration.simpleName.asString()) .build() PropertySpec .builder("TAG", String :: class) .receiver(declaration.toClassName()) .mutable(false) .getter(funSpec) .addOriginatingKSFile(declaration.containingFile !! ) .build() } }
35. override fun process(resolver: Resolver): List<KSAnnotated> { resolver.getSymbolsWithAnnotation(Tag :: class.qualifiedName ! ! ) .filterIsInstance<KSClassDeclaration>() .map { declaration -> val funSpec = FunSpec .getterBuilder() .addStatement("return %S", declaration.simpleName.asString()) .build() PropertySpec .builder("TAG", String :: class) .receiver(declaration.toClassName()) .mutable(false) .getter(funSpec) .addOriginatingKSFile(declaration.containingFile !! ) .build() } .toList() }
36. override fun process(resolver: Resolver): List<KSAnnotated> { resolver.getSymbolsWithAnnotation(Tag :: class.qualifiedName ! ! ) .filterIsInstance<KSClassDeclaration>() .map { declaration -> val funSpec = FunSpec .getterBuilder() .addStatement("return %S", declaration.simpleName.asString()) .build() PropertySpec .builder("TAG", String :: class) .receiver(declaration.toClassName()) .mutable(false) .getter(funSpec) .addOriginatingKSFile(declaration.containingFile !! ) .build() } .toList() .takeIf { it.isNotEmpty() } }
37. override fun process(resolver: Resolver): List<KSAnnotated> { resolver.getSymbolsWithAnnotation(Tag :: class.qualifiedName ! ! ) .filterIsInstance<KSClassDeclaration>() .map { declaration -> val funSpec = FunSpec .getterBuilder() .addStatement("return %S", declaration.simpleName.asString()) .build() PropertySpec .builder("TAG", String :: class) .receiver(declaration.toClassName()) .mutable(false) .getter(funSpec) .addOriginatingKSFile(declaration.containingFile !! ) .build() } .toList() .takeIf { it.isNotEmpty() } ?. let { propertySpecs -> FileSpec .builder("com.tagger.generated", "Tags") .addProperties(propertySpecs) .build() } }
38. override fun process(resolver: Resolver): List<KSAnnotated> { resolver.getSymbolsWithAnnotation(Tag :: class.qualifiedName ! ! ) .filterIsInstance<KSClassDeclaration>() .map { declaration -> val funSpec = FunSpec .getterBuilder() .addStatement("return %S", declaration.simpleName.asString()) .build() PropertySpec .builder("TAG", String :: class) .receiver(declaration.toClassName()) .mutable(false) .getter(funSpec) .addOriginatingKSFile(declaration.containingFile !! ) .build() } .toList() .takeIf { it.isNotEmpty() } ?. let { propertySpecs -> FileSpec .builder("com.tagger.generated", "Tags") .addProperties(propertySpecs) .build() } ?. writeTo(codeGenerator, true) }
39. override fun process(resolver: Resolver): List<KSAnnotated> { resolver.getSymbolsWithAnnotation(Tag :: class.qualifiedName ! ! ) .filterIsInstance<KSClassDeclaration>() .map { declaration -> val funSpec = FunSpec .getterBuilder() .addStatement("return %S", declaration.simpleName.asString()) .build() PropertySpec .builder("TAG", String :: class) .receiver(declaration.toClassName()) .mutable(false) .getter(funSpec) .addOriginatingKSFile(declaration.containingFile !! ) .build() } .toList() .takeIf { it.isNotEmpty() } ?. let { propertySpecs -> FileSpec .builder("com.tagger.generated", "Tags") .addProperties(propertySpecs) .build() } ?. writeTo(codeGenerator, true) return emptyList() }
40. override fun process(resolver: Resolver): List<KSAnnotated> { resolver.getSymbolsWithAnnotation(Tag :: class.qualifiedName ! ! ) .filterIsInstance<KSClassDeclaration>() .map { declaration -> val funSpec = FunSpec .getterBuilder() .addStatement("return %S", declaration.simpleName.asString()) .build() PropertySpec .builder("TAG", String :: class) .receiver(declaration.toClassName()) .mutable(false) .getter(funSpec) .addOriginatingKSFile(declaration.containingFile !! ) .build() } .toList() .takeIf { it.isNotEmpty() } ?. let { propertySpecs -> FileSpec .builder("com.tagger.generated", "Tags") .addProperties(propertySpecs) .build() } ?. writeTo(codeGenerator, true) return emptyList() }
41. Generated Code package com.tagger.generated import com.droidcon.Droidcon import kotlin.String val Droidcon.TAG : String get() = "Droidcon"
42. Using Generated Code import com.tagger.generated.TAG @Tag object Droidcon { fun doLogging() { Log.d(TAG, "Hello Droidcon") } }
43. Coding with AI is Metaprogramming
44. AI and Metaprogramming Traditional • Correctness • Determinism • Precision AI • Accessibility • Simplicity • Creativity
45. AI and Metaprogramming • Identify patterns • Evaluate risks • Choose how to metaprogram
46. Resources My sample KSP: github.com/anthonycr/Tagger Google’s sample KSP: github.com/google/ksp/tree/main/examples KSP documentation: kotlinlang.org/docs/ksp-quickstart.html KotlinPoet: github.com/square/kotlinpoet Complain about this talk: bsky.app/pro fi le/anthonycr.bsky.social