This removes the need for the special `buildSrc` project and makes prototyping plugins even easier.

== Buildscript dependencies are substituted

     */
    fun getBuildscript(): ScriptHandler =
        host.scriptHandler

    /**
     * Configures the build script classpath for this project.
     *
     * @see [Project.buildscript]
     */
    @Suppress("unused")
    open fun buildscript(block: ScriptHandlerScope.() -> Unit): Unit =
        internalError()

    /**
     * Configures the plugin dependencies for this project.
     *
     * @see [PluginDependenciesSpec]

    @ToBeFixedForConfigurationCache(skip = INVESTIGATE)
    def "changing child specs of the copy task while executing is disallowed"() {
        given:
        file("some-dir/input.txt") << "Data"
        buildScript """
            task copy(type: Copy) {
                outputs.cacheIf { true }
                from ("some-dir")
                into ("build/output")

                doFirst {

        """

        buildFile << """
            gradle.tryClass("project", "$localClassName", project.buildscript.classLoader)
            gradle.tryClass("project", "$dependencyClassName", project.buildscript.classLoader)
        """

        when:
        succeeds("help")

        then:
        outputContains("NOT FOUND [settings] $localClassName")

    override fun getBuildscript(): ScriptHandler =
        host.scriptHandler

    /**
     * Configures the build script classpath for this project.
     *
     * @see [Project.buildscript]
     */
    @Suppress("unused")
    open fun buildscript(block: ScriptHandlerScope.() -> Unit): Unit =
        internalError()

    /**
     * Configures the plugin dependencies for this project.
     *
     * @see [PluginDependenciesSpec]

@UnsupportedWithConfigurationCache(because = "software model")
class CyclicalManagedTypeIntegrationTest extends AbstractIntegrationSpec {

    def "managed types can have cyclical managed type references"() {
        when:
        buildScript '''
            @Managed
            interface Parent {
                String getName()
                void setName(String name)

                Child getChild()
            }

            @Managed

 * <p>
 * <b>This model is internal, and is NOT part of the public Tooling API.</b>
 */
@NonNullApi
public class IsolatedGradleProjectInternal implements Serializable {

    private final DefaultGradleScript buildScript = new DefaultGradleScript();
    private File buildDirectory;
    private File projectDirectory;
    private List<LaunchableGradleTask> tasks = ImmutableList.of();
    private String name;
    private String description;

// tag::locking-classpath[]
buildscript {
    configurations.classpath {
        resolutionStrategy.activateDependencyLocking()
    }
}

// tag::locking-classpath[]
buildscript {
    configurations.classpath {
        resolutionStrategy.activateDependencyLocking()
    }
}

        when:
        buildScript plugin.useDeclaration
        def result = runner()
            .withPluginClasspath([])
            .buildAndFail()

        then:
        !execFailure(result).error.contains("Gradle TestKit (classpath:")
    }

    def "injected classpath is indicated in error message if plugin not found"() {
        when:
        buildScript plugin.useDeclaration