* This method will record extra information as well, like plugin occurrence or declaration location.
     */
    void reportPluginValidationIssue(
            IssueLocality locality, MavenSession mavenSession, MojoDescriptor mojoDescriptor, String issue);

    /**
     * Reports plugin Mojo issues applicable to the Mojo itself.
     * <p>
     * This method will record extra information as well, like plugin occurrence or declaration location.

import org.apache.maven.model.version.ModelVersionParser;

import static org.apache.maven.internal.impl.Utils.nonNull;

/**
 * A wrapper class around a resolver version that works as model version parser as well.
 */
@Named
@Singleton
public class DefaultVersionParser implements VersionParser {
    private final ModelVersionParser modelVersionParser;

    @Inject

 * under the License.
 */
package org.apache.maven.artifact.repository.metadata.io;

import java.io.IOException;

/**
 * Signals a failure to parse the metadata due to invalid syntax (e.g. non well formed XML or unknown elements).
 *
 */
public class MetadataParseException extends IOException {

    /**
     * The one-based index of the line containing the error.
     */
    private final int lineNumber;

    /**
     * Creates a request for the specified plugin by copying settings from the specified build session. If the session
     * has a current project, its plugin repositories will be used as well.
     *
     * @param plugin The plugin for which to resolve a version, must not be {@code null}.
     * @param session The Maven session to use, must not be {@code null}.
     */

  </description>

  <properties>
    <overridden>PARENT</overridden>
    <!-- Test the effective value of this property in the child when "overridden" is defined by child as well -->
    <interpolated>${overridden}</interpolated>
  </properties>

 plexus application; The <<<plexus.core.maven>>> realm contains all of the
 resources required to run Maven. Each subsequent plugin realm contains the
 JAR plugin as well as its dependencies. The realms noted above are setup
 in a hierarchical structure where the resources in the parent realms are
 available but the <<realm is searched first before a search is made in
 the parent realm>>.

        return null;
    }

    public void setRepository(ArtifactRepository remoteRepository) {
        /*
         * NOTE: Metadata at the g:a level contains a collection of available versions. After merging, we can't tell
         * which repository provides which version so the metadata manager must not restrict the artifact resolution to
         * the repository with the most recent updates.
         */
    }

        }

        return repository;
    }

    private boolean isLocalRepository(ArtifactRepository repository) {
        // unfortunately, the API doesn't allow to tell a remote repo and the local repo apart...
        return "local".equals(repository.getId());
    }

      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
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- test projects for each of these
- how to categorize the problems so that the id of the problem can be match to a page with descriptive help and the test
  project
- nice little sample projects that could be run in the core as well as integration tests

All Possible Errors
- invalid lifecycle phase (maybe same as bad CLI param, though you were talking about embedder too)
- <module> specified is not found
- malformed settings
- malformed POM