*/
    public void addExtension(CoreExtension coreExtension) {
        getExtensions().add(coreExtension);
    } // -- void addExtension( CoreExtension )

    /**
     * Method getExtensions.
     *
     * @return List
     */
    public List<CoreExtension> getExtensions() {
        if (this.extensions == null) {
            this.extensions = new ArrayList<CoreExtension>();
        }

                "http://maven.apache.org/EXTENSIONS/1.1.0 https://maven.apache.org/xsd/core-extensions-1.1.0.xsd");
        if ((coreExtensions.getExtensions() != null)
                && (coreExtensions.getExtensions().size() > 0)) {
            for (Iterator iter = coreExtensions.getExtensions().iterator(); iter.hasNext(); ) {
                CoreExtension o = (CoreExtension) iter.next();

        // TODO: destinationDirectory should be part of Javadoc
        javadocs.getRenderedDocumentation().from(javadocAll.flatMap(task -> (DirectoryProperty) task.getExtensions().getExtraProperties().get("destinationDirectory")));

        CheckstyleExtension checkstyle = project.getExtensions().getByType(CheckstyleExtension.class);
        tasks.register("checkstyleApi", Checkstyle.class, task -> {
            task.source(extension.getDocumentedSource());

    @Override
    public void apply(Project project) {
        ProjectLayout layout = project.getLayout();
        TaskContainer tasks = project.getTasks();

        GradleDocumentationExtension extension = project.getExtensions().getByType(GradleDocumentationExtension.class);

        generateReleaseNotes(project, layout, tasks, extension);
    }

        TaskContainer tasks = project.getTasks();
        ObjectFactory objects = project.getObjects();
        ProviderFactory providers = project.getProviders();

        GradleDocumentationExtension extension = project.getExtensions().create("gradleDocumentation", GradleDocumentationExtension.class);
        applyConventions(project, tasks, objects, layout, extension);

    @Override
    public void apply(Project project) {
        ProjectLayout layout = project.getLayout();
        TaskContainer tasks = project.getTasks();

        GradleDocumentationExtension extension = project.getExtensions().getByType(GradleDocumentationExtension.class);
        generateDefaultImports(project, tasks, extension);
        generateUserManual(project, tasks, layout, extension);

    private static final String TASK_NAME = "dokkaGeneratePublicationHtml";

    @Override
    public void apply(Project project) {
        GradleDocumentationExtension documentationExtension = project.getExtensions().getByType(GradleDocumentationExtension.class);
        applyPlugin(project);
        updateDocumentationExtension(project, documentationExtension);
        configurePlugin(project, documentationExtension);
    }

        List<Plugin> extensionPlugins = new ArrayList<>();

        Build build = model.getBuild();

        if (build != null) {
            for (Extension extension : build.getExtensions()) {
                Plugin plugin = new Plugin();
                plugin.setGroupId(extension.getGroupId());
                plugin.setArtifactId(extension.getArtifactId());

                if (org != val) {
                    plugin.setVersion(val);
                }
                // Extensions
                org = plugin.getExtensions();
                val = interpolate(org);
                if (org != val) {
                    plugin.setExtensions(val);
                }
                // Executions
                for (PluginExecution execution : plugin.getExecutions()) {

        }
    }

    protected void mergeBuild_Extensions(
            Build target, Build source, boolean sourceDominant, Map<Object, Object> context) {
        target.setExtensions(
                merge(target.getExtensions(), source.getExtensions(), sourceDominant, new ExtensionKeyComputer()));
    }

    protected void mergeExtension(