[JS IR BE] Move external declarations to a separate IrPackageFragment to not generate code for them

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/compiler.kt

@@ -55,6 +55,8 @@ fun compile(
     ExternalDependenciesGenerator(psi2IrContext.moduleDescriptor, psi2IrContext.symbolTable, psi2IrContext.irBuiltIns)
         .generateUnboundSymbolsAsDependencies(moduleFragment)
 
+    MoveExternalDeclarationsToSeparatePlace().lower(moduleFragment.files)
+
     context.performInlining(moduleFragment)
 
     context.lower(moduleFragment.files)

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/MoveExternalDeclarationsToSeparatePlace.kt

@@ -0,0 +1,45 @@
+/*
+ * Copyright 2010-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license
+ * that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.ir.backend.js.lower
+
+import org.jetbrains.kotlin.backend.common.FileLoweringPass
+import org.jetbrains.kotlin.descriptors.PackageFragmentDescriptor
+import org.jetbrains.kotlin.ir.backend.js.lower.inline.addChild
+import org.jetbrains.kotlin.ir.backend.js.utils.isEffectivelyExternal
+import org.jetbrains.kotlin.ir.declarations.IrExternalPackageFragment
+import org.jetbrains.kotlin.ir.declarations.IrFile
+import org.jetbrains.kotlin.ir.declarations.impl.IrExternalPackageFragmentImpl
+import org.jetbrains.kotlin.ir.symbols.IrExternalPackageFragmentSymbol
+import org.jetbrains.kotlin.name.FqName
+
+class MoveExternalDeclarationsToSeparatePlace : FileLoweringPass {
+    private val packageFragment = IrExternalPackageFragmentImpl(object : IrExternalPackageFragmentSymbol {
+        override val descriptor: PackageFragmentDescriptor
+            get() = error("Operation is unsupported")
+
+        private var _owner: IrExternalPackageFragment? = null
+        override val owner get() = _owner!!
+
+        override val isBound get() = _owner != null
+
+        override fun bind(owner: IrExternalPackageFragment) {
+            _owner = owner
+        }
+    }, FqName.ROOT)
+
+    override fun lower(irFile: IrFile) {
+        val it = irFile.declarations.iterator()
+
+        while (it.hasNext()) {
+            val d = it.next()
+
+            if (d.isEffectivelyExternal()) {
+                it.remove()
+                packageFragment.addChild(d)
+            }
+        }
+    }
+}

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/utils/descriptorBasedUtils.kt

@@ -9,9 +9,11 @@ import org.jetbrains.kotlin.builtins.KotlinBuiltIns
 import org.jetbrains.kotlin.descriptors.*
 import org.jetbrains.kotlin.descriptors.annotations.Annotations
 import org.jetbrains.kotlin.descriptors.impl.ValueParameterDescriptorImpl
+import org.jetbrains.kotlin.ir.declarations.IrDeclaration
 import org.jetbrains.kotlin.ir.declarations.IrTypeParameter
 import org.jetbrains.kotlin.ir.symbols.IrConstructorSymbol
 import org.jetbrains.kotlin.name.Name
+import org.jetbrains.kotlin.resolve.descriptorUtil.isEffectivelyExternal
 import org.jetbrains.kotlin.types.KotlinType
 
 val IrConstructorSymbol.constructedClass get() = descriptor.constructedClass
@@ -46,3 +48,5 @@ fun CallableMemberDescriptor.isFakeOverriddenFromAny(): Boolean {
     }
     return overriddenDescriptors.all { it.isFakeOverriddenFromAny() }
 }
+
+fun IrDeclaration.isEffectivelyExternal() = descriptor.isEffectivelyExternal()

core/descriptors/src/org/jetbrains/kotlin/resolve/DescriptorUtils.kt

@@ -422,6 +422,8 @@ fun MemberDescriptor.isEffectivelyExternal(): Boolean {
     return containingClass != null && containingClass.isEffectivelyExternal()
 }
 
+fun DeclarationDescriptor.isEffectivelyExternal() = this is MemberDescriptor && this.isEffectivelyExternal()
+
 fun isParameterOfAnnotation(parameterDescriptor: ParameterDescriptor): Boolean =
     parameterDescriptor.containingDeclaration.isAnnotationConstructor()