Change 'jvmTarget' backing property visibility to internal.

Allows to check if this property was updated by the user or not.

^KT-45611 In Progress
^KT-43095 In Progress

compiler/cli/cli-common/src/org/jetbrains/kotlin/cli/common/arguments/GradleOption.kt

@@ -17,6 +17,10 @@
 package org.jetbrains.kotlin.cli.common.arguments
 
 import kotlin.reflect.KClass
+import kotlin.reflect.KVisibility
 
 @Retention(AnnotationRetention.RUNTIME)
-annotation class GradleOption(val value: KClass<out DefaultValues> = DefaultValues::class)
+annotation class GradleOption(
+    val value: KClass<out DefaultValues> = DefaultValues::class,
+    val backingFieldVisibility: KVisibility = KVisibility.PRIVATE
+)

compiler/cli/cli-common/src/org/jetbrains/kotlin/cli/common/arguments/K2JVMCompilerArguments.kt

@@ -8,6 +8,7 @@ package org.jetbrains.kotlin.cli.common.arguments
 import org.jetbrains.kotlin.cli.common.messages.CompilerMessageSeverity
 import org.jetbrains.kotlin.cli.common.messages.MessageCollector
 import org.jetbrains.kotlin.config.*
+import kotlin.reflect.KVisibility
 
 class K2JVMCompilerArguments : CommonCompilerArguments() {
     companion object {
@@ -75,7 +76,10 @@ class K2JVMCompilerArguments : CommonCompilerArguments() {
     @Argument(value = "-module-name", valueDescription = "<name>", description = "Name of the generated .kotlin_module file")
     var moduleName: String? by NullableStringFreezableVar(null)
 
-    @GradleOption(DefaultValues.JvmTargetVersions::class)
+    @GradleOption(
+        value = DefaultValues.JvmTargetVersions::class,
+        backingFieldVisibility = KVisibility.INTERNAL
+    )
     @Argument(
         value = "-jvm-target",
         valueDescription = "<version>",

generators/tests/org/jetbrains/kotlin/generators/arguments/GenerateGradleOptions.kt

@@ -22,8 +22,10 @@ import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.utils.Printer
 import java.io.File
 import java.io.PrintStream
+import java.util.*
 import kotlin.reflect.KAnnotatedElement
 import kotlin.reflect.KProperty1
+import kotlin.reflect.KVisibility
 import kotlin.reflect.full.declaredMemberProperties
 import kotlin.reflect.full.withNullability
 
@@ -203,7 +205,8 @@ private fun Printer.generateImpl(
                 generatePropertyDeclaration(property, modifiers = "override", value = "null")
             } else {
                 val backingField = property.backingField()
-                println("private var $backingField: $propertyType? = null")
+                val visibilityModified = property.gradleBackingFieldVisibility.name.lowercase(Locale.US)
+                println("$visibilityModified var $backingField: $propertyType? = null")
                 generatePropertyDeclaration(property, modifiers = "override")
                 withIndent {
                     println("get() = $backingField ?: ${property.gradleDefaultValue}")
@@ -314,6 +317,15 @@ private val KProperty1<*, *>.gradleValues: DefaultValues
 private val KProperty1<*, *>.gradleDefaultValue: String
         get() = gradleValues.defaultValue
 
+private val KProperty1<*, *>.gradleBackingFieldVisibility: KVisibility
+    get() {
+        val fieldVisibility = findAnnotation<GradleOption>()!!.backingFieldVisibility
+        require(fieldVisibility != KVisibility.PUBLIC) {
+            "Backing field should not have public visibility!"
+        }
+        return fieldVisibility
+    }
+
 private val KProperty1<*, *>.gradleReturnType: String
         get() {
             // Set nullability based on Gradle default value

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/dsl/KotlinJvmOptionsBase.kt

@@ -52,7 +52,7 @@ internal abstract class KotlinJvmOptionsBase : org.jetbrains.kotlin.gradle.dsl.K
 
     override var jdkHome: kotlin.String? = null
 
-    private var jvmTargetField: kotlin.String? = null
+    internal var jvmTargetField: kotlin.String? = null
     override var jvmTarget: kotlin.String
         get() = jvmTargetField ?: "1.8"
         set(value) {