// extensionArtifacts
            Set<Artifact> extensionArtifacts = new HashSet<>();
            List<Extension> extensions =
                    project.getModel().getDelegate().getBuild().getExtensions();
            if (extensions != null) {
                for (Extension ext : extensions) {
                    String version;
                    if (ext.getVersion() == null || ext.getVersion().isEmpty()) {

    public boolean isExtensions() {
        return (getExtensions() != null) ? Boolean.parseBoolean(getExtensions()) : false;
    }
            ]]>
          </code>
        </codeSegment>
        <codeSegment>
          <version>4.0.0/4.0.99</version>
          <code>
            <![CDATA[
    public void setExtensions(boolean extensions) {
        setExtensions(String.valueOf(extensions));
    }

    /**

                        isAny(relocation.target.getClassifier()) ? null : relocation.target.getClassifier(),
                        isAny(relocation.target.getExtension()) ? null : relocation.target.getExtension(),
                        isAny(relocation.target.getVersion()) ? null : relocation.target.getVersion(),
                        relocation.global ? "User global relocation" : "User project relocation");

                return session.parseVersionConstraint(dependency.getVersion());
            }

            @Override
            public String getExtension() {
                return getType().getExtension();
            }

            @Override
            public Type getType() {
                String type = dependency.getType();
                return session.requireType(type);

    //
    // Implementation
    //

    private File findArtifact(MavenProject project, Artifact artifact) {
        // POMs are always returned from the file system
        if ("pom".equals(artifact.getExtension())) {
            return project.getFile();
        }

        // First check in the project local repository
        File packagedArtifactFile = findInProjectLocalRepository(artifact);

                            EMPTY,
                            problems,
                            errOn30,
                            Version.V20,
                            p.getExtensions(),
                            p.getKey(),
                            p);

                    validate20EffectivePluginDependencies(problems, p, request);
                }

    @Nonnull
    @Override
    public VersionConstraint getVersion() {
        return session.parseVersionConstraint(coordinate.getVersion());
    }

    @Override
    public String getExtension() {
        return coordinate.getExtension();
    }

    @Nonnull
    @Override
    public String getClassifier() {
        return coordinate.getClassifier();
    }

    @Override
    public boolean equals(Object o) {

    }

    private PluginInfo extractPluginInfo(Artifact artifact) {
        // sanity: jar, no classifier and file exists
        if (artifact != null
                && "jar".equals(artifact.getExtension())
                && "".equals(artifact.getClassifier())
                && artifact.getPath() != null) {
            Path artifactPath = artifact.getPath();
            if (Files.isRegularFile(artifactPath)) {

    }

    @Override
    public String getExtension() {
        return dependency.getArtifact().getExtension();
    }

    @Override
    public Type getType() {
        String type = dependency
                .getArtifact()
                .getProperty(ArtifactProperties.TYPE, dependency.getArtifact().getExtension());
        return session.requireType(type);
    }

    @Nonnull

    }

    @Override
    public Version getBaseVersion() {
        return session.parseVersion(artifact.getBaseVersion());
    }

    @Nonnull
    @Override
    public String getExtension() {
        return artifact.getExtension();
    }

    @Nonnull
    @Override
    public String getClassifier() {
        return artifact.getClassifier();
    }

    @Override
    public boolean isSnapshot() {