return addDependency(groupId, artifactId, version, scope, (Exclusion) null);
        }

        public ProjectBuilder addDependency(
                String groupId, String artifactId, String version, String scope, Exclusion exclusion) {
            return addDependency(groupId, artifactId, version, scope, null, exclusion);
        }

     * @param artifactId The artifact id, may be {@code null}.
     * @param version The version, may be {@code null}.
     * @return The user-friendly artifact id, never {@code null}.
     */
    static String toId(String groupId, String artifactId, String version) {
        return ((groupId != null && !groupId.isEmpty()) ? groupId : "[unknown-group-id]")
                + ':'

    public ModelResolver newCopy() {
        return new ProjectModelResolver(this);
    }

    public ModelSource resolveModel(String groupId, String artifactId, String version)
            throws UnresolvableModelException {
        Artifact pomArtifact = new DefaultArtifact(groupId, artifactId, "", "pom", version);

        try {
            ArtifactRequest request = new ArtifactRequest(pomArtifact, repositories, context);

        assertTrue(value instanceof Collection);

        @SuppressWarnings("unchecked")
        Collection<Artifact> artifacts = (Collection<Artifact>) value;

        assertEquals(1, artifacts.size());

        Artifact result = artifacts.iterator().next();

        assertEquals("org.myco.plugins", result.getGroupId());
    }

    @Test

        private final String groupId;

        private final String artifactId;

        private final int hashCode;

        GAKey(String groupId, String artifactId) {
            this.groupId = (groupId != null) ? groupId : "";
            this.artifactId = (artifactId != null) ? artifactId : "";

            hashCode = Objects.hash(this.groupId, this.artifactId);
        }

        @Override

        packagingRegistry = emptyPackagingRegistry;
    }

    private static Plugin newPlugin(String artifactId, String... goals) {
        return Plugin.newBuilder()
                .groupId("org.apache.maven.plugins")
                .artifactId(artifactId)
                .executions(Arrays.stream(goals)
                        .map(goal -> PluginExecution.newBuilder()

    VersionsMetadata(Artifact artifact, Path path, Date timestamp) {
        super(createRepositoryMetadata(artifact), path, timestamp);
        this.artifact = artifact;
    }

    private static Metadata createRepositoryMetadata(Artifact artifact) {

        Metadata.Builder metadata = Metadata.newBuilder();
        metadata.groupId(artifact.getGroupId());
        metadata.artifactId(artifact.getArtifactId());

        buffer.append("<groupId>").append(artifact.getGroupId()).append("</groupId>");
        buffer.append("<artifactId>").append(artifact.getArtifactId()).append("</artifactId>");
        buffer.append("<version>").append(artifact.getBaseVersion()).append("</version>");
        buffer.append("<packaging>").append(artifact.getType()).append("</packaging>");
        buffer.append("</project>");

        private final String groupId;

        private final String artifactId;

        private final String version;

        protected RelativeProject(String groupId, String artifactId, String version) {
            this.groupId = groupId;
            this.artifactId = artifactId;
            this.version = version;
        }

        public String getGroupId() {

    @Override
    public List<org.eclipse.aether.artifact.Artifact> toArtifacts(Collection<Artifact> artifacts) {
        return artifacts == null ? null : map(artifacts, this::toArtifact);
    }

    @Override
    public org.eclipse.aether.artifact.Artifact toArtifact(Artifact artifact) {
        File file = getService(ArtifactManager.class)
                .getPath(artifact)
                .map(Path::toFile)