context.systemPropertiesOverrides.put(MAVEN_HOME, result.toString());
        } else {
            String mavenHome = System.getProperty(Constants.MAVEN_HOME);
            if (mavenHome == null) {
                throw new ParserException("local mode requires " + Constants.MAVEN_HOME + " Java System Property set");
            }

            Path mavenSystemHome = properties.containsKey("maven.home")
                    ? Paths.get(properties.get("maven.home"))
                    : properties.containsKey("env.MAVEN_HOME") ? Paths.get(properties.get("env.MAVEN_HOME")) : null;

            DefaultRepositorySystemSession rsession = new DefaultRepositorySystemSession(h -> false);
            rsession.setSystemProperties(properties);

/**
 * Configuration constants.
 */
public final class Constants {

    /**
     * Maven home.
     *
     * @since 3.0.0
     */
    @Config(readOnly = true)
    public static final String MAVEN_HOME = "maven.home";

    /**
     * Maven installation configuration directory.
     *
     * @since 4.0.0
     */
    @Config(defaultValue = "${maven.home}/conf")

                .filter(k -> !sys.contains(k.getKey()))
                .forEach(k -> System.setProperty(k.getKey(), k.getValue()));
        System.setProperty(
                Constants.MAVEN_HOME, invokerRequest.installationDirectory().toString());
    }

    protected void validate(C context) throws Exception {}

    protected void prepare(C context) throws Exception {}