assertNotNull(collector.getProblems());
        assertEquals(0, collector.getProblems().size());

        collector.add(null, "MESSAGE1", -1, -1, null);

        Exception e2 = new Exception();
        collector.add(Severity.WARNING, null, 42, 127, e2);

        assertEquals(2, collector.getProblems().size());

        Problem p1 = collector.getProblems().get(0);

            return new DefaultToolchainsBuildingResult(
                    new PersistedToolchains(result.getEffectiveToolchains()), convert(result.getProblems()));
        } catch (ToolchainsBuilderException e) {
            throw new ToolchainsBuildingException(convert(e.getProblems()));
        }
    }

    private Source convert(org.apache.maven.building.Source source) {
        if (source instanceof FileSource fs) {

     *
     * @return The problems that caused this exception, never {@code null}.
     */
    public List<ModelProblem> getProblems() {
        if (result == null) {
            return Collections.emptyList();
        }
        return Collections.unmodifiableList(result.getProblems());
    }

    private static String toMessage(ModelBuildingResult result) {

    public static <T> Result<T> error(Result<?> result) {
        return error(result.getProblems());
    }

    public static <T> Result<T> error(Result<?>... results) {
        final List<ModelProblem> problemsList = new ArrayList<>();

        for (Result<?> result1 : results) {
            for (ModelProblem modelProblem : result1.getProblems()) {
                problemsList.add(modelProblem);
            }
        }

/**
 * Signals one ore more errors during settings building. The settings builder tries to collect as many problems as
 * possible before eventually failing to provide callers with rich error information. Use {@link #getProblems()} to
 * query the details of the failure.
 *
 * @deprecated since 4.0.0, use {@link org.apache.maven.api.services.SettingsBuilder} instead
 */
@Deprecated(since = "4.0.0")

        if (result.getModelIds().isEmpty()) {
            DefaultModelBuildingResult tmp = new DefaultModelBuildingResult();
            tmp.setEffectiveModel(result.getEffectiveModel());
            tmp.setProblems(getProblems());
            tmp.setActiveExternalProfiles(result.getActiveExternalProfiles());
            String id = getRootModelId();
            tmp.addModelId(id);
            tmp.setRawModel(id, getRootModel());

        problemCollector.add(Problem.Severity.ERROR, "MESSAGE", 3, 5, new Exception());
        ToolchainsBuildingException e = new ToolchainsBuildingException(problemCollector.getProblems());
        assertEquals(
                "1 problem was encountered while building the effective toolchains" + LS
                        + "[ERROR] MESSAGE @ line 3, column 5" + LS,
                e.getMessage());
    }

        ProblemCollector collector2 = ProblemCollectorFactory.newInstance(Collections.singletonList(problem));

        assertNotSame(collector1, collector2);
        assertEquals(0, collector1.getProblems().size());
        assertEquals(1, collector2.getProblems().size());
    }

        } else {
            this.activeExternalProfiles.clear();
        }

        return this;
    }

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

    public DefaultModelBuildingResult setProblems(List<ModelProblem> problems) {
        if (problems != null) {
            this.problems = new ArrayList<>(problems);
        } else {
            this.problems.clear();

     *
     * @return The problems that caused this exception, never {@code null}.
     */
    public List<ModelProblem> getProblems() {
        if (result == null) {
            return Collections.emptyList();
        }
        return Collections.unmodifiableList(result.getProblems());
    }