[K/JS] Support KClass<*>.createInstance reflection method ^KT-58684 Fixed

libraries/stdlib/api/js/kotlin.js.kt

@@ -216,6 +216,15 @@ public final annotation class ExperimentalJsFileName : kotlin.Annotation {
     public constructor ExperimentalJsFileName()
 }
 
+@kotlin.RequiresOptIn(level = Level.WARNING)
+@kotlin.annotation.Retention(value = AnnotationRetention.BINARY)
+@kotlin.annotation.Target(allowedTargets = {AnnotationTarget.CLASS, AnnotationTarget.ANNOTATION_CLASS, AnnotationTarget.PROPERTY, AnnotationTarget.FIELD, AnnotationTarget.LOCAL_VARIABLE, AnnotationTarget.VALUE_PARAMETER, AnnotationTarget.CONSTRUCTOR, AnnotationTarget.FUNCTION, AnnotationTarget.PROPERTY_GETTER, AnnotationTarget.PROPERTY_SETTER, AnnotationTarget.TYPEALIAS})
+@kotlin.annotation.MustBeDocumented
+@kotlin.SinceKotlin(version = "1.9")
+public final annotation class ExperimentalJsReflectionCreateInstance : kotlin.Annotation {
+    public constructor ExperimentalJsReflectionCreateInstance()
+}
+
 public external object JSON {
     public final fun <T> parse(text: kotlin.String): T
 

libraries/stdlib/api/js/kotlin.reflect.kt

@@ -7,6 +7,10 @@ public inline fun <reified T> typeOf(): kotlin.reflect.KType
 @kotlin.internal.LowPriorityInOverloadResolution
 public fun <T : kotlin.Any> kotlin.reflect.KClass<T>.cast(value: kotlin.Any?): T
 
+@kotlin.SinceKotlin(version = "1.9")
+@kotlin.js.ExperimentalJsReflectionCreateInstance
+public fun <T : kotlin.Any> kotlin.reflect.KClass<T>.createInstance(): T
+
 @kotlin.reflect.ExperimentalAssociatedObjects
 public inline fun <reified T : kotlin.Annotation> kotlin.reflect.KClass<*>.findAssociatedObject(): kotlin.Any?
 

libraries/stdlib/common/src/kotlin/JsAnnotationsH.kt

@@ -6,6 +6,7 @@
 package kotlin.js
 
 import kotlin.annotation.AnnotationTarget.*
+import kotlin.reflect.KClass
 
 /**
  * Gives a declaration (a function, a property or a class) specific name in JavaScript.
@@ -100,3 +101,30 @@ public expect annotation class JsExport() {
     public annotation class Ignore()
 }
 
+
+/**
+ * This annotation marks the experimental Kotlin/JS reflection API that allows to create an instance of provided [KClass]
+ * The API can be removed completely in any further release.
+ *
+ * Any usage of a declaration annotated with `@ExperimentalJsReflectionCreateInstance` should be accepted either by
+ * annotating that usage with the [OptIn] annotation, e.g. `@OptIn(ExperimentalJsReflectionCreateInstance::class)`,
+ * or by using the compiler argument `-opt-in=kotlin.js.ExperimentalJsReflectionCreateInstance`.
+ */
+@RequiresOptIn(level = RequiresOptIn.Level.WARNING)
+@Retention(AnnotationRetention.BINARY)
+@Target(
+    AnnotationTarget.CLASS,
+    AnnotationTarget.ANNOTATION_CLASS,
+    AnnotationTarget.PROPERTY,
+    AnnotationTarget.FIELD,
+    AnnotationTarget.LOCAL_VARIABLE,
+    AnnotationTarget.VALUE_PARAMETER,
+    AnnotationTarget.CONSTRUCTOR,
+    AnnotationTarget.FUNCTION,
+    AnnotationTarget.PROPERTY_GETTER,
+    AnnotationTarget.PROPERTY_SETTER,
+    AnnotationTarget.TYPEALIAS
+)
+@MustBeDocumented
+@SinceKotlin("1.9")
+public annotation class ExperimentalJsReflectionCreateInstance

libraries/stdlib/js-ir/runtime/BitMask.kt

@@ -8,8 +8,8 @@ package kotlin.js
 internal typealias BitMask = IntArray
 
 private fun bitMaskWith(activeBit: Int): BitMask {
-    val intArray = IntArray((activeBit shr 5) + 1)
     val numberIndex = activeBit shr 5
+    val intArray = IntArray(numberIndex + 1)
     val positionInNumber = activeBit and 31
     val numberWithSettledBit = 1 shl positionInNumber
     intArray[numberIndex] = intArray[numberIndex] or numberWithSettledBit

libraries/stdlib/js-ir/runtime/jsIntrinsics.kt

@@ -227,4 +227,7 @@ internal fun jsInIntrinsic(lhs: Any?, rhs: Any): Boolean
 internal fun jsDelete(e: Any?)
 
 @JsIntrinsic
-internal fun jsContextfulRef(context: dynamic, fn: dynamic): dynamic
+internal fun jsContextfulRef(context: dynamic, fn: dynamic): dynamic
+
+@JsIntrinsic
+internal fun jsIsEs6(): Boolean

libraries/stdlib/js-ir/runtime/metadataUtils.kt

@@ -7,9 +7,10 @@ package kotlin.js
 internal fun setMetadataFor(
     ctor: Ctor,
     name: String?,
-    metadataConstructor: (name: String?, associatedObjectKey: Number?, associatedObjects: dynamic, suspendArity: Array<Int>?) -> Metadata,
+    metadataConstructor: (name: String?, defaultConstructor: dynamic, associatedObjectKey: Number?, associatedObjects: dynamic, suspendArity: Array<Int>?) -> Metadata,
     parent: Ctor?,
     interfaces: Array<dynamic>?,
+    defaultConstructor: dynamic,
     associatedObjectKey: Number?,
     associatedObjects: dynamic,
     suspendArity: Array<Int>?
@@ -21,7 +22,7 @@ internal fun setMetadataFor(
         """)
     }
 
-    val metadata = metadataConstructor(name, associatedObjectKey, associatedObjects, suspendArity ?: js("[]"))
+    val metadata = metadataConstructor(name, defaultConstructor, associatedObjectKey, associatedObjects, suspendArity ?: js("[]"))
     ctor.`$metadata$` = metadata
 
     if (interfaces != null) {
@@ -45,16 +46,34 @@ private fun generateInterfaceId(): Int {
 }
 
 
-internal fun interfaceMeta(name: String?, associatedObjectKey: Number?, associatedObjects: dynamic, suspendArity: Array<Int>?): Metadata {
-    return createMetadata("interface", name, associatedObjectKey, associatedObjects, suspendArity, generateInterfaceId())
+internal fun interfaceMeta(
+    name: String?,
+    defaultConstructor: dynamic,
+    associatedObjectKey: Number?,
+    associatedObjects: dynamic,
+    suspendArity: Array<Int>?
+): Metadata {
+    return createMetadata("interface", name, defaultConstructor, associatedObjectKey, associatedObjects, suspendArity, generateInterfaceId())
 }
 
-internal fun objectMeta(name: String?, associatedObjectKey: Number?, associatedObjects: dynamic, suspendArity: Array<Int>?): Metadata {
-    return createMetadata("object", name, associatedObjectKey, associatedObjects, suspendArity, null)
+internal fun objectMeta(
+    name: String?,
+    defaultConstructor: dynamic,
+    associatedObjectKey: Number?,
+    associatedObjects: dynamic,
+    suspendArity: Array<Int>?
+): Metadata {
+    return createMetadata("object", name, defaultConstructor, associatedObjectKey, associatedObjects, suspendArity, null)
 }
 
-internal fun classMeta(name: String?, associatedObjectKey: Number?, associatedObjects: dynamic, suspendArity: Array<Int>?): Metadata {
-    return createMetadata("class", name, associatedObjectKey, associatedObjects, suspendArity, null)
+internal fun classMeta(
+    name: String?,
+    defaultConstructor: dynamic,
+    associatedObjectKey: Number?,
+    associatedObjects: dynamic,
+    suspendArity: Array<Int>?
+): Metadata {
+    return createMetadata("class", name, defaultConstructor, associatedObjectKey, associatedObjects, suspendArity, null)
 }
 
 // Seems like we need to disable this check if variables are used inside js annotation
@@ -62,6 +81,7 @@ internal fun classMeta(name: String?, associatedObjectKey: Number?, associatedOb
 private fun createMetadata(
     kind: String,
     name: String?,
+    defaultConstructor: dynamic,
     associatedObjectKey: Number?,
     associatedObjects: dynamic,
     suspendArity: Array<Int>?,
@@ -75,6 +95,7 @@ private fun createMetadata(
     associatedObjects: associatedObjects,
     suspendArity: suspendArity,
     ${'$'}kClass$: undef,
+    defaultConstructor: defaultConstructor,
     iid: iid
 })""")
 }
@@ -90,6 +111,7 @@ internal external interface Metadata {
     val iid: Int?
 
     var `$kClass$`: dynamic
+    val defaultConstructor: dynamic
 
     var errorInfo: Int? // Bits set for overridden properties: "message" => 0x1, "cause" => 0x2
 }

libraries/stdlib/js-ir/runtime/reflectRuntime.kt

@@ -44,7 +44,7 @@ private fun getKPropMetadata(paramCount: Int, setter: Any?): dynamic {
 }
 
 private fun metadataObject(): Metadata {
-    return classMeta(VOID, VOID, VOID, VOID)
+    return classMeta(VOID, VOID, VOID, VOID, VOID)
 }
 
 private val propertyRefClassMetadataCache: Array<Array<dynamic>> = arrayOf<Array<dynamic>>(

libraries/stdlib/js-ir/src/kotlin/reflect/createInstance.kt

@@ -0,0 +1,28 @@
+/*
+ * Copyright 2010-2023 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package kotlin.reflect
+
+/**
+ * Creates a new instance of the class, calling a constructor which either has no parameters or all parameters of which have
+ * a default value. If there are no or many such constructors, an exception is thrown.
+ */
+@OptIn(JsIntrinsic::class)
+@SinceKotlin("1.9")
+@ExperimentalJsReflectionCreateInstance
+public fun <T : Any> KClass<T>.createInstance(): T {
+    val jsClass = js.asDynamic()
+
+    if (jsClass === js("Object")) return js("{}")
+
+    val noArgsConstructor = jsClass.`$metadata$`.unsafeCast<Metadata?>()?.defaultConstructor
+        ?: throw IllegalArgumentException("Class \"$simpleName\" should have a single no-arg constructor")
+
+    return if (jsIsEs6() && noArgsConstructor !== jsClass) {
+        js("noArgsConstructor.call(jsClass)")
+    } else {
+        js("new noArgsConstructor()")
+    }
+}