/**
     * Register the given listener which will receive all events.
     *
     * @param listener the listener to register
     * @throws NullPointerException if {@code listener} is null
     */
    void registerListener(@Nonnull Listener listener);

    /**
     * Unregisters a previously registered listener.
     *
     * @param listener the listener to unregister

        ModelBuildingListener listener = getModelBuildingListener(request);

        if (listener != null) {
            AtomicReference<Model> m = new AtomicReference<>(model);

            ModelBuildingEvent event = new DefaultModelBuildingEvent(model, m::set, request, problems);

            catapult.accept(listener, event);

            return m.get();
        }

            this.modelCache = modelCache;
            return this;
        }

        public ModelBuilderRequestBuilder listener(Object listener) {
            this.listener = listener;
            return this;
        }

        public ModelBuilderRequestBuilder interimResult(ModelBuilderResult interimResult) {
            this.interimResult = interimResult;

                            .source(modelSource)
                            .projectBuild(true)
                            .locationTracking(true)
                            .listener(listener)
                            .build();

                    if (pomFile != null) {
                        project.setRootDirectory(rootLocator.findRoot(pomFile.getParent()));
                    }

    }

    @Override
    public void registerListener(@Nonnull Listener listener) {
        listeners.add(nonNull(listener));
    }

    @Override
    public void unregisterListener(@Nonnull Listener listener) {
        listeners.remove(nonNull(listener));
    }

    @Nonnull
    @Override
    public Collection<Listener> getListeners() {
        return Collections.unmodifiableCollection(listeners);