[Gradle] Don't register 'sourceSets' container dynamically

Before this change created via 'KotlinJvmFactory'
'AndroidProjectExtension' and 'JvmProjectExtension' instances are
missing source sets container as it was added dynamically in the plugin.

On the other hand, there are no use-cases to add such a container
dynamically.

^KT-72467 Verification Pending

libraries/tools/kotlin-gradle-plugin/api/external/kotlin-gradle-plugin.api

@@ -298,7 +298,7 @@ public abstract class org/jetbrains/kotlin/gradle/dsl/KotlinMultiplatformExtensi
 	public static synthetic fun withSourcesJar$default (Lorg/jetbrains/kotlin/gradle/dsl/KotlinMultiplatformExtension;ZILjava/lang/Object;)V
 }
 
-public class org/jetbrains/kotlin/gradle/dsl/KotlinProjectExtension : org/jetbrains/kotlin/gradle/dsl/KotlinBaseExtension, org/jetbrains/kotlin/gradle/plugin/HasProject, org/jetbrains/kotlin/tooling/core/HasMutableExtras {
+public abstract class org/jetbrains/kotlin/gradle/dsl/KotlinProjectExtension : org/gradle/api/plugins/ExtensionAware, org/jetbrains/kotlin/gradle/dsl/KotlinBaseExtension, org/jetbrains/kotlin/gradle/plugin/HasProject, org/jetbrains/kotlin/tooling/core/HasMutableExtras {
 	public field coreLibrariesVersion Ljava/lang/String;
 	public fun <init> (Lorg/gradle/api/Project;)V
 	public fun explicitApi ()V

libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/dsl/KotlinProjectExtension.kt

@@ -5,11 +5,12 @@
 
 package org.jetbrains.kotlin.gradle.dsl
 
+import com.gradle.scan.agent.serialization.scan.serializer.kryo.it
 import org.gradle.api.Action
 import org.gradle.api.Named
 import org.gradle.api.NamedDomainObjectContainer
 import org.gradle.api.Project
-import org.gradle.api.internal.plugins.DslObject
+import org.gradle.api.plugins.ExtensionAware
 import org.gradle.api.provider.Property
 import org.gradle.jvm.toolchain.JavaLanguageVersion
 import org.gradle.jvm.toolchain.JavaToolchainSpec
@@ -19,6 +20,7 @@ import org.jetbrains.kotlin.gradle.plugin.*
 import org.jetbrains.kotlin.gradle.plugin.KotlinPluginLifecycle.CoroutineStart.Undispatched
 import org.jetbrains.kotlin.gradle.plugin.mpp.KotlinAndroidTarget
 import org.jetbrains.kotlin.gradle.plugin.mpp.KotlinWithJavaTarget
+import org.jetbrains.kotlin.gradle.plugin.sources.DefaultKotlinSourceSetFactory
 import org.jetbrains.kotlin.gradle.targets.js.dsl.KotlinJsTargetDsl
 import org.jetbrains.kotlin.gradle.targets.js.ir.KotlinJsIrSingleTargetPreset
 import org.jetbrains.kotlin.gradle.tasks.CompileUsingKotlinDaemon
@@ -77,21 +79,28 @@ internal fun KotlinBaseExtension.explicitApiModeAsCompilerArg(): String? {
 }
 
 @KotlinGradlePluginPublicDsl
-open class KotlinProjectExtension @Inject constructor(
+abstract class KotlinProjectExtension @Inject constructor(
     override val project: Project
 ) : KotlinBaseExtension,
     HasMutableExtras,
-    HasProject {
+    HasProject,
+    ExtensionAware {
 
     override lateinit var coreLibrariesVersion: String
 
     final override val extras: MutableExtras = mutableExtrasOf()
 
+    private val sourceSetsContainer = project.objects.domainObjectContainer(
+        KotlinSourceSet::class.java,
+        DefaultKotlinSourceSetFactory(project)
+    ).also { kotlinSourceSets ->
+        // Required for Gradle to generate accessors to source sets or 'sourceSets {}' DSL
+        extensions.add("sourceSets", kotlinSourceSets)
+    }
     override var sourceSets: NamedDomainObjectContainer<KotlinSourceSet>
-        @Suppress("UNCHECKED_CAST")
-        get() = DslObject(this).extensions.getByName("sourceSets") as NamedDomainObjectContainer<KotlinSourceSet>
-        internal set(value) {
-            DslObject(this).extensions.add("sourceSets", value)
+        get() = sourceSetsContainer
+        @Deprecated("Assigning new value to 'sourceSets' is deprecated", level = DeprecationLevel.ERROR)
+        internal set(_) {
         }
 
     internal suspend fun awaitSourceSets(): NamedDomainObjectContainer<KotlinSourceSet> {

libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/plugin/KotlinPluginWrapper.kt

@@ -17,7 +17,6 @@
 package org.jetbrains.kotlin.gradle.plugin
 
 import org.gradle.api.GradleException
-import org.gradle.api.NamedDomainObjectFactory
 import org.gradle.api.Plugin
 import org.gradle.api.Project
 import org.gradle.api.artifacts.ExternalDependency
@@ -41,7 +40,6 @@ import org.jetbrains.kotlin.gradle.plugin.internal.*
 import org.jetbrains.kotlin.gradle.plugin.mpp.*
 import org.jetbrains.kotlin.gradle.plugin.mpp.apple.swiftexport.internal.initSwiftExportClasspathConfigurations
 import org.jetbrains.kotlin.gradle.plugin.mpp.resources.resolve.KotlinTargetResourcesResolutionStrategy
-import org.jetbrains.kotlin.gradle.plugin.sources.DefaultKotlinSourceSetFactory
 import org.jetbrains.kotlin.gradle.plugin.statistics.BuildFusService
 import org.jetbrains.kotlin.gradle.report.BuildMetricsService
 import org.jetbrains.kotlin.gradle.targets.js.KotlinJsCompilerAttribute
@@ -195,9 +193,6 @@ abstract class KotlinBasePluginWrapper : DefaultKotlinBasePlugin() {
 
     abstract val pluginVariant: String
 
-    internal open fun kotlinSourceSetFactory(project: Project): NamedDomainObjectFactory<KotlinSourceSet> =
-        DefaultKotlinSourceSetFactory(project)
-
     override fun apply(project: Project) {
         super.apply(project)
         project.logger.info("Using Kotlin Gradle Plugin $pluginVariant variant")
@@ -212,14 +207,6 @@ abstract class KotlinBasePluginWrapper : DefaultKotlinBasePlugin() {
 
         project.createKotlinExtension(projectExtensionClass).apply {
             coreLibrariesVersion = pluginVersion
-
-            fun kotlinSourceSetContainer(factory: NamedDomainObjectFactory<KotlinSourceSet>) =
-                project.container(KotlinSourceSet::class.java, factory)
-
-            val topLevelExtension = project.topLevelExtension
-            if (topLevelExtension is KotlinProjectExtension) {
-                project.kotlinExtension.sourceSets = kotlinSourceSetContainer(kotlinSourceSetFactory(project))
-            }
         }
 
         project.extensions.add(KotlinTestsRegistry.PROJECT_EXTENSION_NAME, createTestRegistry(project))

libraries/tools/kotlin-gradle-plugin/src/functionalTest/kotlin/org/jetbrains/kotlin/gradle/unitTests/KotlinCompileApiTest.kt

@@ -22,6 +22,7 @@ import org.junit.Test
 import org.junit.rules.TemporaryFolder
 import kotlin.test.assertEquals
 import kotlin.test.assertNotEquals
+import kotlin.test.assertNotNull
 
 class KotlinCompileApiTest {
 
@@ -199,6 +200,7 @@ class KotlinCompileApiTest {
         jvmExtension.compilerOptions.jvmTarget.set(JvmTarget.JVM_21)
         jvmExtension.compilerOptions.javaParameters.set(true)
         jvmExtension.explicitApi = ExplicitApiMode.Strict
+        jvmExtension.sourceSets.register("main")
 
         project.evaluate()
 
@@ -208,6 +210,7 @@ class KotlinCompileApiTest {
             ExplicitApiMode.Strict,
             (jvmTask.get() as KotlinCompile).explicitApiMode.get()
         )
+        assertNotNull(jvmExtension.sourceSets.findByName("main"))
     }
 
     @Test
@@ -231,6 +234,7 @@ class KotlinCompileApiTest {
         androidExtension.compilerOptions.jvmTarget.set(JvmTarget.JVM_21)
         androidExtension.compilerOptions.javaParameters.set(true)
         androidExtension.explicitApi = ExplicitApiMode.Strict
+        androidExtension.sourceSets.register("main")
 
         project.evaluate()
 
@@ -240,6 +244,7 @@ class KotlinCompileApiTest {
             ExplicitApiMode.Strict,
             (androidTask.get() as KotlinCompile).explicitApiMode.get()
         )
+        assertNotNull(androidExtension.sourceSets.findByName("main"))
     }
 
     @Test