* @return the collection result, never {@code null}
     * @throws DependencyCollectorException if the dependency tree could not be built
     * @throws IllegalArgumentException if an argument is null or invalid
     *
     * @see DependencyCollector#collect(Session, Project)
     * @see DependencyCollector#collect(Session, DependencyCoordinate)
     * @see DependencyCollector#collect(Session, Artifact)
     */
    @Nonnull

        if (event.getMetadata().getFile() != null) {
            metadata = event.getMetadata().getFile();
        } else {
            metadata = event.getMetadata();
        }

        String errorType = " is invalid";
        if (exception instanceof FileNotFoundException) {
            errorType = " is inaccessible";
        }

        String msg = "";
        if (exception != null) {

    /**
     * Provides new {@link Transport} instance for given {@link RemoteRepository}, if possible.
     *
     * @throws TransportProviderException if passed in remote repository has invalid remote URL or unsupported protocol.
     */
    @Nonnull
    Transport transport(@Nonnull Session session, @Nonnull RemoteRepository repository);

            // MNG-5368: Log a message instead of returning 'null' silently.
            this.logger.error(
                    String.format(
                            "Invalid version specification '%s' creating dependency artifact '%s'.", d.getVersion(), d),
                    e);
            return null;
        }

        Artifact artifact = artifactFactory.createDependencyArtifact(

        } else if (MavenExecutionRequest.REACTOR_FAIL_FAST.equals(rootSession.getReactorFailureBehavior())) {
            buildContext.getReactorBuildStatus().halt();
        } else {
            logger.error("invalid reactor failure behavior " + rootSession.getReactorFailureBehavior());
            buildContext.getReactorBuildStatus().halt();
        }
    }

    public static void attachToThread(MavenProject currentProject) {

        pluginValidator.validate(pluginArtifact, pluginDescriptor, errors);

        if (!errors.isEmpty()) {
            throw new InvalidPluginDescriptorException(
                    "Invalid plugin descriptor for " + plugin.getId() + " (" + pluginFile + ")", errors);
        }

        pluginDescriptor.setPluginArtifact(pluginArtifact);

        return pluginDescriptor;
    }

        }
        try {
            return ValidationReportLevel.valueOf(level.toUpperCase(Locale.ENGLISH));
        } catch (IllegalArgumentException e) {
            logger.warn(
                    "Invalid value specified for property {}: '{}'. Supported values are (case insensitive): {}",
                    MAVEN_PLUGIN_VALIDATION_KEY,
                    level,
                    Arrays.toString(ValidationReportLevel.values()));

            if (!"pom".equals(parentModel.getPackaging())) {
                problems.add(
                        Severity.ERROR,
                        ModelProblem.Version.BASE,
                        "Invalid packaging for parent POM " + ModelProblemUtils.toSourceHint(parentModel)
                                + ", must be \"pom\" but is \"" + parentModel.getPackaging() + "\"",

                        Collections.emptyList());
            } catch (InvalidVersionSpecificationException e) {
                throw new ArtifactMetadataRetrievalException("Invalid version creating artifacts", e, artifact);
            }
        }

        private String getKey(Artifact artifact) {
            return artifact.getDependencyConflictId();
        }

import org.apache.maven.api.services.ModelBuilderRequest;
import org.apache.maven.api.services.ModelProblemCollector;

/**
 * Checks the model for missing or invalid values.
 *
 */
public interface ModelValidator {
    /**
     * Checks the specified file model for missing or invalid values. This model is directly created from the POM
     * file and has not been subjected to inheritance, interpolation or profile/default injection.
     *