if (pluginArtifactRepositories == null) {
            pluginArtifactRepositories = new ArrayList<>();
        }
        return pluginArtifactRepositories;
    }

    // TODO this does not belong here.
    @Override
    public ProjectBuildingRequest getProjectBuildingRequest() {
        if (projectBuildingRequest == null) {
            projectBuildingRequest = new DefaultProjectBuildingRequest();