[cls] include property constant initializer in stubs

^KTIJ-24667
this would allow building FirElements from stubs

core/descriptors/src/org/jetbrains/kotlin/renderer/DescriptorRenderer.kt

@@ -12,6 +12,7 @@ import org.jetbrains.kotlin.descriptors.annotations.AnnotationUseSiteTarget
 import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.name.FqNameUnsafe
 import org.jetbrains.kotlin.name.Name
+import org.jetbrains.kotlin.resolve.constants.ConstantValue
 import org.jetbrains.kotlin.types.KotlinType
 import org.jetbrains.kotlin.types.TypeConstructor
 import org.jetbrains.kotlin.types.TypeProjection
@@ -233,6 +234,7 @@ interface DescriptorRendererOptions {
     var boldOnlyForNamesInHtml: Boolean
 
     var includePropertyConstant: Boolean
+    var propertyConstantRenderer: ((ConstantValue<*>) -> String?)?
     var parameterNameRenderingPolicy: ParameterNameRenderingPolicy
     var withoutTypeParameters: Boolean
     var receiverAfterName: Boolean

core/descriptors/src/org/jetbrains/kotlin/renderer/DescriptorRendererImpl.kt

@@ -491,9 +491,10 @@ internal class DescriptorRendererImpl(
         return (defaultList + argumentList).sorted()
     }
 
-    private fun renderConstant(value: ConstantValue<*>): String {
+    private fun renderConstant(value: ConstantValue<*>): String? {
+        options.propertyConstantRenderer?.let { return it.invoke(value) }
         return when (value) {
-            is ArrayValue -> value.value.joinToString(", ", "{", "}") { renderConstant(it) }
+            is ArrayValue -> value.value.mapNotNull { renderConstant(it) }.joinToString(", ", "{", "}")
             is AnnotationValue -> renderAnnotation(value.value).removePrefix("@")
             is KClassValue -> when (val classValue = value.value) {
                 is KClassValue.Value.LocalClass -> "${classValue.type}::class"
@@ -986,7 +987,8 @@ internal class DescriptorRendererImpl(
     private fun renderInitializer(variable: VariableDescriptor, builder: StringBuilder) {
         if (includePropertyConstant) {
             variable.compileTimeInitializer?.let { constant ->
-                builder.append(" = ").append(escape(renderConstant(constant)))
+                val renderedConstant = renderConstant(constant)
+                if (renderedConstant != null) builder.append(" = ").append(escape(renderedConstant))
             }
         }
     }

core/descriptors/src/org/jetbrains/kotlin/renderer/DescriptorRendererOptionsImpl.kt

@@ -20,6 +20,7 @@ import org.jetbrains.kotlin.builtins.KotlinBuiltIns
 import org.jetbrains.kotlin.descriptors.ValueParameterDescriptor
 import org.jetbrains.kotlin.descriptors.annotations.AnnotationDescriptor
 import org.jetbrains.kotlin.name.FqName
+import org.jetbrains.kotlin.resolve.constants.ConstantValue
 import org.jetbrains.kotlin.types.KotlinType
 import java.lang.IllegalStateException
 import java.lang.reflect.Modifier
@@ -87,6 +88,7 @@ internal class DescriptorRendererOptionsImpl : DescriptorRendererOptions {
     override var actualPropertiesInPrimaryConstructor: Boolean by property(false)
     override var uninferredTypeParameterAsName by property(false)
     override var includePropertyConstant by property(false)
+    override var propertyConstantRenderer: ((ConstantValue<*>) -> String?)? by property(null)
     override var withoutTypeParameters by property(false)
     override var withoutSuperTypes by property(false)
     override var typeNormalizer by property<(KotlinType) -> KotlinType>({ it })