* users to migrate their projects.
     */
    int VALIDATION_LEVEL_MAVEN_2_0 = 20;

    /**
     * Denotes validation as performed by Maven 3.0. This validation level is meant for existing projects.
     */
    int VALIDATION_LEVEL_MAVEN_3_0 = 30;

    /**

                projectPrefixValueSource =
                        new ProblemDetectingValueSource(projectPrefixValueSource, PREFIX_POM, PREFIX_PROJECT, problems);
            }

            prefixlessObjectBasedValueSource = new ObjectBasedValueSource(model);
            if (request.getValidationLevel() >= ModelBuilderRequest.VALIDATION_LEVEL_MAVEN_2_0) {

            resultModel = pluginConfigurationExpander.expandPluginConfiguration(resultModel, request, problems);
        }

        result.setEffectiveModel(resultModel);

        // effective model validation
        modelValidator.validateEffectiveModel(resultModel, request, problems);

        if (hasModelErrors(problems)) {
            throw problems.newModelBuilderException();
        }

        return result;

    }

    /* MNG-4193 */
    @Test
    void testValidationErrorUponNonUniquePluginRepositoryId() throws Exception {
        assertThrows(
                ProjectBuildingException.class,
                () -> buildPom("unique-repo-id/plugin-repo"),
                "Non-unique repository ids did not cause validation error");
    }

    /* MNG-4193 */

     *
     * @return The assembled model, never {@code null}.
     */
    @Nonnull
    Model getEffectiveModel();

    /**
     * Gets the specified raw model as it was read from a model source. Apart from basic validation, a raw model has not
     * undergone any updates by the model builder, e.g. reflects neither inheritance nor interpolation. The model

        request.projectBuild(true);
        request.session(InternalSession.from(session));
        request.source(ModelSource.fromPath(src));
        request.validationLevel(ModelBuilderRequest.VALIDATION_LEVEL_MINIMAL);
        request.locationTracking(false);
        request.modelResolver(modelResolver);
        request.transformerContextBuilder(modelBuilder.newTransformerContextBuilder());

        }

        if (request.getValidationLevel() >= ModelBuilderRequest.VALIDATION_LEVEL_MAVEN_2_0) {
            Severity errOn31 = getSeverity(request, ModelBuilderRequest.VALIDATION_LEVEL_MAVEN_3_1);

            validateBannedCharacters(
                    EMPTY, "version", problems, errOn31, Version.V20, m.getVersion(), null, m, ILLEGAL_VERSION_CHARS);

                                    e.getModelId(), e.getMessage(), pomFile != null ? pomFile.toFile() : null, e);
                        }
                        // validation error, continue project building and delay failing to help IDEs
                        error = e;
                    }

                    modelProblems = result.getProblems();

  | o add specification element to a field, this would be more a technical description of
  |   what is allowed in the field.
  |
  | o validators: there could be several levels of validation. Simple type validation could
  |   be done with a regex, but we need inter-field validation and rules which could be
  |   dealt with by something like drools.
  |
  | o i18n: would be good to be able to have names/descriptions/specifications

    }

    /**
     * Validate the specified settings.
     *
     * @param settings The settings to validate, must not be {@code null}.
     * @param isProjectSettings Boolean indicating if the validation is for project settings or user / global settings.
     * @return The list of problems that were encountered, must not be {@code null}.
     */
    @Nonnull