filesystem, it will continue to be available.

  The question remaining is: Which level of offline mode will we support? It
  seems reasonable to assume that users will be able to tell when localhost is
  not active (in most cases, localhost should be available, even if the rest of
  the network is not). Therefore, let's concentrate on the state where no

 * <li>unlimited number of version components,</li>
 * <li>version components in the text can be digits or strings,</li>
 * <li>strings are checked for well-known qualifiers and the qualifier ordering is used for version ordering.
 *     Well-known qualifiers (case insensitive) are:<ul>
 *     <li><code>alpha</code> or <code>a</code></li>
 *     <li><code>beta</code> or <code>b</code></li>

        // This is often an artifact like a POM that is taken from disk and we already have hold of the
        // file reference. But this may be a Maven Plugin that we need to resolve from a remote repository
        // as well as its dependencies.

        if (request.isResolveRoot() /* && rootArtifact.getFile() == null */) {
            try {
                resolve(rootArtifact, request.getRemoteRepositories(), session);

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}.
     */

- 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

 * is thread safe.
 * <p>
 * Important: Given the instance of supplier memorizes the supplier {@link RepositorySystem} instance it supplies,
 * their lifecycle is shared as well: once supplied repository system is shut-down, this instance becomes closed as
 * well. Any subsequent {@code getXXX} method invocation attempt will fail with {@link IllegalStateException}.
 */
public class RepositorySystemSupplier implements Supplier<RepositorySystem> {

                }
            }
        }

        /*
         * MNG-4312: We neither have reserved all of the above magic expressions nor is their set fixed/well-known (it
         * gets occasionally extended by newer Maven versions). This imposes the risk for existing plugins to
         * unintentionally use such a magic expression for an ordinary property. So here we check whether we

 "Software"), to  deal in  the Software without  restriction, including
 without limitation  the rights to  use, copy, modify,  merge, publish,
 distribute,  sublicense, and/or sell  copies of  the Software,  and to
 permit persons to whom the Software  is furnished to do so, subject to
 the following conditions:

 The  above  copyright  notice  and  this permission  notice  shall  be