[Gradle] Getting a root project of root gradle after project loading

#KT-59863 Fixed

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/kotlin/org/jetbrains/kotlin/gradle/mpp/MppCompositeBuildIT.kt

@@ -364,4 +364,14 @@ class MppCompositeBuildIT : KGPBaseTest() {
             }
         }
     }
+
+    @GradleTest
+    @GradleTestVersions(minVersion = TestVersions.Gradle.G_7_0)
+    fun `test sample7`(gradleVersion: GradleVersion) {
+        val producer = project("mpp-composite-build/sample7-KT-59863-pluginManagement.includeBuild/producerBuild", gradleVersion)
+        project("mpp-composite-build/sample7-KT-59863-pluginManagement.includeBuild/consumerBuild", gradleVersion, defaultBuildOptions) {
+            settingsGradleKts.toFile().replaceText("<producer_path>", producer.projectPath.toUri().path)
+            build("projects")
+        }
+    }
 }

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/mpp-composite-build/sample7-KT-59863-pluginManagement.includeBuild/consumerBuild/settings.gradle.kts

@@ -0,0 +1,7 @@
+pluginManagement {
+    includeBuild("<producer_path>")
+}
+
+plugins {
+    id("org.jetbrains.example.gradle.plugin")
+}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/mpp-composite-build/sample7-KT-59863-pluginManagement.includeBuild/producerBuild/example-gradle-plugin/build.gradle.kts

@@ -0,0 +1,18 @@
+plugins {
+    `java-gradle-plugin`
+    kotlin("jvm")
+}
+
+repositories {
+    mavenLocal()
+    mavenCentral()
+}
+
+gradlePlugin {
+    plugins {
+        create("exampleGradlePlugin") {
+            id = "org.jetbrains.example.gradle.plugin"
+            implementationClass = "ExampleGradlePlugin"
+        }
+    }
+}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/mpp-composite-build/sample7-KT-59863-pluginManagement.includeBuild/producerBuild/example-gradle-plugin/src/main/kotlin/ExampleGradlePlugin.kt

@@ -0,0 +1,12 @@
+/*
+ * 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.
+ */
+
+import org.gradle.api.Plugin
+import org.gradle.api.initialization.Settings
+
+class ExampleGradlePlugin : Plugin<Settings> {
+    override fun apply(target: Settings) {
+    }
+}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/mpp-composite-build/sample7-KT-59863-pluginManagement.includeBuild/producerBuild/multiplatform-subproject/build.gradle.kts

@@ -0,0 +1,11 @@
+plugins {
+    kotlin("multiplatform")
+}
+
+repositories {
+    mavenCentral()
+}
+
+kotlin {
+    jvm()
+}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/mpp-composite-build/sample7-KT-59863-pluginManagement.includeBuild/producerBuild/settings.gradle.kts

@@ -0,0 +1 @@
+include("example-gradle-plugin", "multiplatform-subproject")

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

@@ -10,11 +10,11 @@ import com.google.gson.JsonObject
 import com.google.gson.JsonParser
 import com.google.gson.stream.JsonWriter
 import org.gradle.api.Project
+import org.gradle.api.plugins.ExtensionAware
 import org.gradle.api.tasks.Input
 import org.gradle.api.tasks.Internal
 import org.gradle.api.tasks.Nested
 import org.jetbrains.kotlin.gradle.dsl.KotlinMultiplatformExtension
-import org.jetbrains.kotlin.gradle.dsl.multiplatformExtensionOrNull
 import org.jetbrains.kotlin.gradle.plugin.mpp.pm20.GradleKpmModule
 import org.jetbrains.kotlin.gradle.plugin.mpp.pm20.util.currentBuildId
 import org.jetbrains.kotlin.gradle.plugin.sources.KotlinDependencyScope
@@ -419,10 +419,12 @@ internal object GlobalProjectStructureMetadataStorage {
     fun propertyName(buildName: String, projectPath: String) = "$propertyPrefix.$buildName.path.$projectPath"
 
     fun registerProjectStructureMetadata(project: Project, metadataProvider: () -> KotlinProjectStructureMetadata) {
-        project.compositeBuildRootProject.extensions.extraProperties.set(
-            propertyName(project.currentBuildId().name, project.path),
-            { metadataProvider().toJson() }
-        )
+        project.compositeBuildRootProject {
+            (it as ExtensionAware).extensions.extraProperties.set(
+                propertyName(project.currentBuildId().name, project.path),
+                { metadataProvider().toJson() }
+            )
+        }
     }
 
     fun getProjectStructureMetadataProvidersFromAllGradleBuilds(project: Project): Map<ProjectPathWithBuildName, Lazy<KotlinProjectStructureMetadata?>> {

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

@@ -17,7 +17,13 @@ import kotlin.reflect.KClass
 val Gradle.projectCacheDir
     get() = startParameter.projectCacheDir ?: this.rootProject.projectDir.resolve(".gradle")
 
-internal val Project.compositeBuildRootProject: Project get() = generateSequence(project.gradle) { it.parent }.last().rootProject
+internal val Project.compositeBuildRootGradle: Gradle get() = generateSequence(project.gradle) { it.parent }.last()
+internal val Project.compositeBuildRootProject: Project get() = compositeBuildRootGradle.rootProject
+
+/**
+ * Run block function on root project of the root build in composite build only when a root project becomes available
+ */
+internal fun Project.compositeBuildRootProject(block: (Project) -> Unit) = compositeBuildRootGradle.rootProject(block)
 
 internal fun <T : BuildService<P>, P : BuildServiceParameters> Gradle.registerClassLoaderScopedBuildService(
     serviceClass: KClass<T>,