* is optional or mandatory), and possible exclusions for transitive dependencies.
 * The {@linkplain #getVersionConstraint() version} and the {@linkplain #getOptional() obligation}
 * may not be defined precisely.
 *
 * @since 4.0.0
 */
@Experimental
@Immutable
public interface DependencyCoordinates extends ArtifactCoordinates {
    /**

  private static final Collector<Object, ?, Optional<Object>> TO_OPTIONAL =
      Collector.of(
          ToOptionalState::new,
          ToOptionalState::add,
          ToOptionalState::combine,
          ToOptionalState::getOptional,
          Collector.Characteristics.UNORDERED);

  /**
   * A collector that converts a stream of zero or one elements to an {@code Optional}.
   *

                && Objects.equals(d1.getScope(), d2.getScope())
                && Objects.equals(d1.getSystemPath(), d2.getSystemPath())
                && Objects.equals(d1.getOptional(), d2.getOptional())
                && equals(d1.getExclusions(), d2.getExclusions());
    }

    private boolean equals(Collection<Exclusion> ce1, Collection<Exclusion> ce2) {
        if (ce1.size() == ce2.size()) {

     * The value is computed during the dependencies collection phase.
     *
     * @return {@code true} if the dependency is optional, or {@code false} if mandatory
     * @see DependencyCoordinates#getOptional()
     */
    boolean isOptional();

    /**
     * {@return coordinates with the same identifiers as this dependency}
     */
    @Nonnull
    @Override
    DependencyCoordinates toCoordinates();

            exclusions.add(convert(exclusion));
        }

        return new Dependency(
                artifact,
                dependency.getScope(),
                dependency.getOptional() != null ? dependency.isOptional() : null,
                exclusions);
    }

    private Exclusion convert(org.apache.maven.model.Exclusion exclusion) {

                String scope = dependency.getScope() != null ? dependency.getScope() : "";
                return session.requireDependencyScope(scope);
            }

            @Override
            public Boolean getOptional() {
                return dependency.isOptional();
            }

            @Nonnull
            @Override
            public Collection<Exclusion> getExclusions() {

abstract class BuildTimestampValueSource : ValueSource<String, BuildTimestampValueSource.Parameters>, Describable {

    interface Parameters : ValueSourceParameters {

        @get:Optional
        val buildTimestampFromBuildReceipt: Property<String>

        @get:Optional
        val buildTimestampFromGradleProperty: Property<String>

        val runningOnCi: Property<Boolean>

        val runningInstallTask: Property<Boolean>

    @get:Input
    abstract val baseVersion: Property<String>

    @get:Input
    @get:Optional
    abstract val commitId: Property<String>

    @get:Input
    abstract val snapshot: Property<Boolean>

    @get:Input
    abstract val promotionBuild: Property<Boolean>

    @get:Input
    @get:Optional
    abstract val buildTimestamp: Property<Date>

    @get:OutputDirectory

    public boolean isSelectedVersionKnown() throws OverConstrainedVersionException {
        return artifact.isSelectedVersionKnown();
    }

    /** {@inheritDoc} */
    public void setOptional(boolean optional) {
        artifact.setOptional(optional);
    }

    /** {@inheritDoc} */
    public int hashCode() {
        int result = 17;

        result = 37 * result + getGroupId().hashCode();

    void setRelease(boolean release);

    List<ArtifactVersion> getAvailableVersions();

    void setAvailableVersions(List<ArtifactVersion> versions);

    boolean isOptional();

    void setOptional(boolean optional);

    ArtifactVersion getSelectedVersion() throws OverConstrainedVersionException;

    boolean isSelectedVersionKnown() throws OverConstrainedVersionException;