K2のKotlin IDEプラグインの中を覗いてみよう♪

この春、K2コンパイラを使った、IntelliJ IDEAのKotlinプラグインのアルファ版が発表されました。見慣れたIDEが軽くなり、さらに、スイスイとコードを書ける感覚を目指したプラグインの開発がどんどん進んでいます。
K2の洗練された仕組みによって、コードの解析がかなり早くなりました。しかも、プラグインに新しいコンパイラが入っただけではありません。早くて安定するために、それぞれの部分をゼロから作り直したり、大幅に改善されたりしています。

Kotlinチームのメンバーとして、その変化について具体的にお話しさせていただきます。
難しそうだと感じる人もいるかもしれませんが、コンパイラやIDEの内部に触れたことがない人でもわかりやすい内容になっています。皆さんがよく知っているKotlinに、違う角度から触れてみましょう！

Transcript

1. Yan Zhulanow, JetBrains June 2024 K2 meets the IDE. So let’s peek inside!
2. Jet
3. Jet
4. Compiler IDE Plugin
5. Compiler IDE Plugin
7. Jetpack Compose Let’s write UI in Kotlin! Code tr a nsform a tion needed Implement in the new BE
8. Jetpack Compose Let’s write UI in Kotlin! Code tr a nsform a tion needed Implement in the new BE
9. Gradle Kotlin DSL Let’s write build scripts in Kotlin! Not enough script m a gic Design extensible script de f initions
10. Gradle Kotlin DSL Let’s write build scripts in Kotlin! Not enough script m a gic Design extensible script de f initions
11. Sometimes, it goes the hard way expect/act u a l binding Mixed KMP compil a tion
12. Sometimes, it goes the hard way expect/act u a l binding Mixed KMP compil a tion
14. K2
15. Parser fu n main(a r gs: A rr a y <St r ing>) { va l name = a r gs.sing l eO r N ull () ?: "Anon y mo u s" p r int l n("He ll o, $name!") }
16. Parser fu n main(a r gs: A rr a y <St r ing>) { va l name = a r gs.sing l eO r N ull () ?: "Anon y mo u s" p r int l n("He ll o, $name!") } main a r gs: A rr a y <St r ing> A rr a y <St r ing> St r ing A rr a y va l name = a r gs.sing l eO r N ull () ?: "Anon y mo u s" p r int l n("He l l o, $name!") name a r gs.sing l eO r N ull () ?: "Anon y mo u s" a r gs.sing l eO r N ull () "Anon y mo u s" a r gs sing l eO r N ull p r int l n "He ll o, $name!" a r gs “He ll o, " name
17. Parser fu n main(a r gs: A rr a y <St r ing>) { va l name = a r gs.sing l eO r N ull () ?: "Anon y mo u s" p r int l n("He ll o, $name!") } main a r gs: A rr a y <St r ing> A rr a y <St r ing> St r ing A rr a y va l name = a r gs.sing l eO r N ull () ?: "Anon y mo u s" p r int l n("He l l o, $name!") name a r gs.sing l eO r N ull () ?: "Anon y mo u s" a r gs.sing l eO r N ull () "Anon y mo u s" a r gs sing l eO r N ull p r int l n "He ll o, $name!" a r gs “He ll o, " name fun println(text: String) { throw RuntimeException(text) // 😈 }
18. Semantic Analyzer Type resolution C a ll resolution Type inference V a rious checkers P a rser Code gener a tion Addition a l st a tic checks ☕.c l ass
19. Compiler IDE Plugin
20. Compiler IDE Plugin Use the s a me API! BindingContext Dec l a r ationDesc r ipto r K ot l inT y pe Reso l vedCa ll ana l y ze()
21. Compiler IDE Plugin BindingContext Dec l a r ationDesc r ipto r K ot l inT y pe Reso l vedCa ll ana l y ze() Debugger Ref a ctorings Completion Inspections Type Hier a rchy Highlighting
22. Compiler IDE Plugin BindingContext Dec l a r ationDesc r ipto r K ot l inT y pe Reso l vedCa ll ana l y ze() Debugger Ref a ctorings Completion Inspections Type Hier a rchy Highlighting K2
23. Compiler IDE Plugin K2
25. How compilers work Lexer P a rser Sem a ntic a n a lyzer Code Gener a tor
26. How IDEs work
27. Multi-module Compilation B a se App Kotlin Stdlib Coroutines Compose module module libr a ry libr a ry libr a ry Compil a tion of B a se Kotlin Stdlib Coroutines B a se Compil a tion of App Kotlin Stdlib Coroutines B a se.j a r Compose App
28. Inside the IDE B a se App Kotlin Stdlib Coroutines Compose module module libr a ry libr a ry libr a ry
30. Wh a t w a s wrong with the old IDE?
31. Lazy Compiler class LazyClassDescriptor(val psi: KtClassOrObject, storageManager: StorageManager) { val companionObject: ClassDescriptor by storageManager.createLazyValue(::computeCompanionObject) private fun computeCompanionObject(): ClassDescriptor { ... } } Compiler represent a tion of a cl a ss (simpli f ied) interface StorageManager { fun <K, V : Any> createMemoizedFunction(compute: (K) -> V): MemoizedFunctionToNotNull<K, V> fun <T : Any> createLazyValue(computable: () -> T): NotNullLazyValue<T> fun <T : Any> createNullableLazyValue(computable: () -> T?): NullableLazyValue<T> fun <T> compute(computable: () -> T): T } L a zy v a lue provider (simpli f ied)
32. One lock to rule them all class LockBasedStorageManager(val lock: SimpleLock) : StorageManager { override fun <T : Any> createLazyValue(computable: () -> T): NotNullLazyValue<T> { return LockBasedNotNullLazyValue<T>(computable) } private inner class LockBasedNotNullLazyValue<T : Any>(val computable: () -> T) : NullableLazyValue<T> { override fun isComputed(): Boolean { ... } override fun isComputing(): Boolean { ... } override fun invoke(): T? { lock.lock() try { // Computation and caching } finally { lock.unlock() } } } } The only l a zy v a lue provider implement a tion (simpli f ied)
33. Here we go again enum class FirResolvePhase { RAW_FIR, IMPORTS, COMPILER_REQUIRED_ANNOTATIONS, COMPANION_GENERATION, SUPER_TYPES, SEALED_CLASS_INHERITORS, TYPES, STATUS, EXPECT_ACTUAL_MATCHING, CONTRACTS, IMPLICIT_TYPES_BODY_RESOLVE, CONSTANT_EVALUATION, ANNOTATION_ARGUMENTS, BODY_RESOLVE } No implicit l a ziness!
34. SUPER_TYPES Phase sealed class ConeKotlinType : ConeKotlinTypeProjection(), KotlinTypeMarker, TypeArgumentListMarker { final override val kind: ProjectionKind get() = ProjectionKind.INVARIANT abstract val typeArguments: Array<out ConeTypeProjection> final override val type: ConeKotlinType get() = this abstract val nullability: ConeNullability abstract val attributes: ConeAttributes final override fun toString(): String { return renderForDebugging() } abstract override fun equals(other: Any?): Boolean abstract override fun hashCode(): Int }
35. TYPES Phase sealed class ConeKotlinType : ConeKotlinTypeProjection(), KotlinTypeMarker, TypeArgumentListMarker { final override val kind: ProjectionKind get() = ProjectionKind.INVARIANT abstract val typeArguments: Array<out ConeTypeProjection> final override val type: ConeKotlinType get() = this abstract val nullability: ConeNullability abstract val attributes: ConeAttributes final override fun toString(): String { return renderForDebugging() } abstract override fun equals(other: Any?): Boolean abstract override fun hashCode(): Int }
36. BODY_RESOLVE Phase sealed class ConeKotlinType : ConeKotlinTypeProjection(), KotlinTypeMarker, TypeArgumentListMarker { final override val kind: ProjectionKind get() = ProjectionKind.INVARIANT abstract val typeArguments: Array<out ConeTypeProjection> final override val type: ConeKotlinType get() = this abstract val nullability: ConeNullability abstract val attributes: ConeAttributes final override fun toString(): String { return renderForDebugging() } abstract override fun equals(other: Any?): Boolean abstract override fun hashCode(): Int }
37. IMPORTS COMPILER_REQUIRED_ANNOTATIONS COMPANION_GENERATION SUPER_TYPES SEALED_CLASS_INHERITORS TYPES STATUS EXPECT_ACTUAL_MATCHING CONTRACTS IMPLICIT_TYPES_BODY_RESOLVE CONSTANT_EVALUATION ANNOTATION_ARGUMENTS BODY_RESOLVE 17.5% 35% 52.5% 70%
38. fun isSubClassOf(subClass: FirClass, superClass: FirClass, useSiteSession: FirSession): Boolean { subClass.lazyResolveToPhase(FirResolvePhase.SUPER_TYPES) if (subClass.superConeTypes.any { it.toRegularClassSymbol(useSiteSession) == superClass.symbol }) { return true } return subClass.superConeTypes .asSequence() .mapNotNull { it.toRegularClassSymbol(useSiteSession) } .any { isSubClassOf(it.fir, superClass, useSiteSession) } } No implicit laziness Now super types a re resolved for s u bC l ass
39. Why a re you telling me a ll of this? 🤔 🤔 🤔 🤔 🤔 🤔 🤔
40. Debugger Ref a ctorings Completion Intentions Type Hier a rchy Highlighting C a ll Hier a rchy Post f ix templ a tes N a vig a tion J a v a to Kotlin Converter Find Us a ges Quick Fixes Line M a rkers
41. Debugger Ref a ctorings Completion Intentions Type Hier a rchy Highlighting C a ll Hier a rchy Post f ix templ a tes N a vig a tion J a v a to Kotlin Converter Find Us a ges Quick Fixes Line M a rkers
42. Local phases enum class FirResolvePhase { RAW_FIR, IMPORTS, COMPILER_REQUIRED_ANNOTATIONS, COMPANION_GENERATION, SUPER_TYPES, SEALED_CLASS_INHERITORS, TYPES, STATUS, EXPECT_ACTUAL_MATCHING, CONTRACTS, IMPLICIT_TYPES_BODY_RESOLVE, CONSTANT_EVALUATION, ANNOTATION_ARGUMENTS, BODY_RESOLVE }
43. Local phases enum class FirResolvePhase { RAW_FIR, IMPORTS, COMPILER_REQUIRED_ANNOTATIONS, COMPANION_GENERATION, SUPER_TYPES, SEALED_CLASS_INHERITORS, TYPES, STATUS, EXPECT_ACTUAL_MATCHING, CONTRACTS, IMPLICIT_TYPES_BODY_RESOLVE, CONSTANT_EVALUATION, ANNOTATION_ARGUMENTS, BODY_RESOLVE }
44. Jumping phases enum class FirResolvePhase { RAW_FIR, IMPORTS, COMPILER_REQUIRED_ANNOTATIONS, COMPANION_GENERATION, SUPER_TYPES, SEALED_CLASS_INHERITORS, TYPES, STATUS, EXPECT_ACTUAL_MATCHING, CONTRACTS, IMPLICIT_TYPES_BODY_RESOLVE, CONSTANT_EVALUATION, ANNOTATION_ARGUMENTS, BODY_RESOLVE }
45. interface Foo interface Bar : Foo SUPER_TYPES Phase
46. interface Foo : Bar interface Bar : Foo SUPER_TYPES Phase
47. Jumping phases enum class FirResolvePhase { RAW_FIR, IMPORTS, COMPILER_REQUIRED_ANNOTATIONS, COMPANION_GENERATION, SUPER_TYPES, SEALED_CLASS_INHERITORS, TYPES, STATUS, EXPECT_ACTUAL_MATCHING, CONTRACTS, IMPLICIT_TYPES_BODY_RESOLVE, CONSTANT_EVALUATION, ANNOTATION_ARGUMENTS, BODY_RESOLVE }
48. Jumping phases enum class FirResolvePhase { RAW_FIR, IMPORTS, COMPILER_REQUIRED_ANNOTATIONS, COMPANION_GENERATION, SUPER_TYPES, SEALED_CLASS_INHERITORS, TYPES, STATUS, EXPECT_ACTUAL_MATCHING, CONTRACTS, IMPLICIT_TYPES_BODY_RESOLVE, CONSTANT_EVALUATION, ANNOTATION_ARGUMENTS, BODY_RESOLVE } 100% p a r a llel!
49. No sem a ntic highlighting
57. It’s not only about sources App Kotlin stdlib kotlinx.coroutines Compose JDK Ktor koin okio
58. // c l ass ve r sion 65.0 (65) // access fl ags 0x21 p u b l ic c l ass test/MainJava { / / compi l ed fr om: MainJava.java / / access fl ags 0x1 p u b l ic <init>()V / / access fl ags 0x9 p u b l ic static main([Ljava/ l ang/St r ing;)V } Java metadata
59. // c l ass ve r sion 52.0 (52) // access fl ags 0x31 p u b l ic f ina l c l ass test/Main K ot l in K t { / / compi l ed fr om: Main K ot l in. k t @L k ot l in/Metadata;( mv={1, 9, 0}, k =2, xi=48, d1={“\ u 0000\ u 0014\n\ u 0000 .. . \ u 0006\ u 0006”}, d2={"main", "", "a r gs", "", "", "([Ljava/ l ang/St r ing;)V", “Test"} ) / / access fl ags 0x19 p u b l ic f ina l static main([Ljava/ l ang/St r ing;)V // annotab l e pa r amete r co u nt: 1 (invisib l e) @Lo r g/jetb r ains/annotations/NotN u ll ;() / / invisib l e, pa r amete r 0 } Kotlin Metadata
60. message T y peA l ias { optiona l int32 f l ags = 1 [de f a ul t = 6 /* p u b l ic, no annotations */ ]; r eq u i r ed int32 name = 2 [(name_id_in_tab l e) = t ru e]; r epeated T y pePa r amete r t y pe_pa r amete r = 3; optiona l T y pe u nde rly ing_t y pe = 4; optiona l int32 u nde rl y ing_t y pe_id = 5 [(t y pe_id_in_tab l e) = t ru e]; optiona l T y pe expanded_t y pe = 6; optiona l int32 expanded_t y pe_id = 7 [(t y pe_id_in_tab l e) = t ru e]; r epeated Annotation annotation = 8; / / Index into the Ve r sionReq u i r ementTab l e r epeated int32 ve r sion_ r eq u i r ement = 31; Extensions 100 to 199; } Protobuf inside
61. Lazy libraries class DeserializedClassDescriptor( outerContext: DeserializationContext, val classProto: ProtoBuf.Class, nameResolver: NameResolver ) : AbstractClassDescriptor(...), DeserializedDescriptor { private val primaryConstructor = c.storageManager.createNullableLazyValue { computePrimaryConstructor() } private fun computePrimaryConstructor(): ClassConstructorDescriptor? { if (kind.isSingleton) { return DescriptorFactory.createPrimaryConstructorForObject(this, SourceElement.NO_SOURCE).apply { returnType = getDefaultType() } } return classProto.constructorList.firstOrNull { !Flags.IS_SECONDARY.get(it.flags) }?.let { constructorProto -> c.memberDeserializer.loadConstructor(constructorProto, true) } } ... } Compiler represent a tion of a libr a ry cl a ss (simpli f ied)
62. From the IntelliJ IDEA document a tion (https://plugins.jetbr a ins.com/docs/intellij/stub-indexes.html) Use the stubs, Luke
63. pac k age test fu n main(a r gs: A rr a y <St r ing>) { va l name = a r gs.sing l eO r N ull () ?: "Anon y mo u s" p r int l n("He ll o, $name!") } PAC K AGE_DIRECTIVE REFERENCE_EXPRESSION(name = test) IMPORT_LIST FUN( f qName = test.main, isExtension = f a l se, hasB l oc k Bod y = f a l se) VALUE_PARAMETER_LIST VALUE_PARAMETER(name = a r gs, hasDe f a u l tVa l u e = f a l se) TYPE_REFERENCE USER_TYPE REFERENCE_EXPRESSION(name = A rr a y ) TYPE_ARGUMENT_LIST TYPE_PROJECTION( k ind = NONE) TYPE_REFERENCE USER_TYPE REFERENCE_EXPRESSION(name = St r ing) Gener a ted stub Source f ile
64. P P PP PPPP Stubs
65. Stubs
66. Compiler plugins Compiler plugin
67. Compiler plugins Compiler plugin Gr a dle plugin M a ven plugin
68. Compiler plugins Compiler plugin IDE Plugin Gr a dle plugin M a ven plugin
69. Compiler plugins Compiler plugin
70. Much more than code analysis Auto-completion Ref a ctorings Scripting support Ev a lu a te expression
71. How to try?
72. there is one more thing
73. The missing piece
74. Kotlin Analysis API Provides bin a ry comp a tibility Documented Migr a tion guides
75. Kotlin Analysis API Provides bin a ry comp a tibility Documented Migr a tion guides Coming this summer
76. Beyond the IDE An a lysis API IDE Plugin
77. Beyond the IDE An a lysis API IDE Plugin CLI Tools