? Collections.emptyList()
                : Collections.unmodifiableList(topologicallySortedProjects);
    }

    @Override
    public DependencyResolutionResult getDependencyResolutionResult() {
        return dependencyResolutionResult;
    }

    @Override
    public MavenExecutionResult setDependencyResolutionResult(DependencyResolutionResult dependencyResolutionResult) {

     *
     * @return The result of the dependency resolution for the project or {@code null} if the project dependencies were
     *         not requested.
     */
    DependencyResolutionResult getDependencyResolutionResult();

     */
    List<MavenProject> getTopologicallySortedProjects();

    MavenExecutionResult setDependencyResolutionResult(DependencyResolutionResult result);

    DependencyResolutionResult getDependencyResolutionResult();

    // for each exception
    // - knowing what artifacts are missing
    // - project building exception
    // - invalid project model exception: list of markers
    // - xmlpull parser exception

        return project;
    }

    @Override
    public List<ModelProblem> getProblems() {
        return problems;
    }

    @Override
    public DependencyResolutionResult getDependencyResolutionResult() {
        return dependencyResolutionResult;
    }

                @Nonnull
                @Override
                public Optional<DependencyResolverResult> getDependencyResolverResult() {
                    return Optional.ofNullable(res.getDependencyResolutionResult())
                            .map(r -> new DefaultDependencyResolverResult(
                                    null, r.getCollectionErrors(), session.getNode(r.getDependencyGraph()), 0));
                }