return get(id, classPath, parent, filterSpec, null);
    }

    @Override
    public ClassLoader createIfAbsent(ClassLoaderId id, ClassPath classPath, @Nullable ClassLoader parent, Function<ClassLoader, ClassLoader> factoryFunction, @Nullable HashCode implementationHash) {
        return factoryFunction.apply(parent);
    }

     *
     * @param id the ID of the classloader.
     * @return the classloader.
     */
    ClassLoader createIfAbsent(ClassLoaderId id, ClassPath classPath, @Nullable ClassLoader parent, Function<ClassLoader, ClassLoader> factoryFunction, @Nullable HashCode implementationHash);

    /**
     * Discards the given classloader.
     */

        def classPath = classPath("root")

        when:
        def result = cache.createIfAbsent(id1, classPath, parent, { ClassLoader spec -> loader } as Function, null)

        then:
        result == loader
        cache.size() == 1

        when:
        def result2 = cache.createIfAbsent(id1, classPath, parent, { throw new RuntimeException() } as Function, null)

        then:

        listener.childScopeCreated(parent.getId(), id, origin);
        ClassLoaderId classLoaderId = id.localId();
        if (localClassLoaderFactory != null) {
            localClassLoader = classLoaderCache.createIfAbsent(classLoaderId, classPath, parent.getExportClassLoader(), localClassLoaderFactory, classpathImplementationHash);
        } else {

        return doGet(id, classPath, parent, filterSpec, implementationHash, this::createClassLoader);
    }

    @Override
    public ClassLoader createIfAbsent(ClassLoaderId id, ClassPath classPath, @Nullable ClassLoader parent, Function<ClassLoader, ClassLoader> factoryFunction, @Nullable HashCode implementationHash) {