name: Feature Enhancement Request
description: I want to make an existing feature better
labels: ["type=enhancement"]
body:
  - type: markdown
    attributes:
      value: >
        Filing feature requests is one of the most popular ways to contribute to Guava.


        Be aware, though: most feature requests are not accepted, even if they're suggested by
        a full-time Guava team member. [Feedback](https://stackoverflow.com/a/4543114) from our

 *
 * @author George van den Driessche
 */
@GwtCompatible
public final class TesterRequirements {
  private final Set<Feature<?>> presentFeatures;
  private final Set<Feature<?>> absentFeatures;

  public TesterRequirements(Set<Feature<?>> presentFeatures, Set<Feature<?>> absentFeatures) {
    this.presentFeatures = Helpers.copyToSet(presentFeatures);
    this.absentFeatures = Helpers.copyToSet(absentFeatures);
  }

          annotationClass.getDeclaringClass(),
          returnType.getComponentType());
    }
  }

  // This is public so that tests for Feature enums we haven't yet imagined
  // can reuse it.
  public static <E extends Enum<?> & Feature<?>> void assertGoodFeatureEnum(
      Class<E> featureEnumClass) {
    final Class<?>[] classes = featureEnumClass.getDeclaredClasses();
    for (Class<?> containedClass : classes) {

@SuppressWarnings("rawtypes") // maybe avoidable if we rework the whole package?
@GwtCompatible
public enum MultisetFeature implements Feature<Multiset> {
  /**
   * Indicates that elements from {@code Multiset.entrySet()} update to reflect changes in the
   * backing multiset.
   */
  ENTRIES_ARE_VIEWS;

  @Override
  public Set<Feature<? super Multiset>> getImpliedFeatures() {
    return Collections.emptySet();
  }

    }

    @Override
    public Iterable<E> order(List<E> insertionOrder) {
      return gen.order(insertionOrder);
    }
  }

  private static Set<Feature<?>> computeReserializedCollectionFeatures(Set<Feature<?>> features) {
    Set<Feature<?>> derivedFeatures = new HashSet<>(features);
    derivedFeatures.remove(SERIALIZABLE);
    derivedFeatures.remove(SERIALIZABLE_INCLUDING_VIEWS);
    return derivedFeatures;
  }

We make changes to Guava's public [APIs][], including adding new APIs, very
carefully. Because of this, if you're interested in seeing a new feature in
Guava, the best approach is to create an [issue][] (or comment on an existing
issue if there is one) requesting the feature and describing specific use cases
for it.

If the feature has merit, it will go through a thorough process of API design
and review. Any code should come after this.

    }

    @Override
    public Iterable<E> order(List<E> insertionOrder) {
      return gen.order(insertionOrder);
    }
  }

  private static Set<Feature<?>> computeReserializedCollectionFeatures(Set<Feature<?>> features) {
    Set<Feature<?>> derivedFeatures = new HashSet<>(features);
    derivedFeatures.remove(SERIALIZABLE);
    derivedFeatures.remove(SERIALIZABLE_INCLUDING_VIEWS);
    return derivedFeatures;
  }

 */
@GwtIncompatible // java.util.Arrays#copyOf(Object[], int), java.lang.reflect.Array
public class CompactHashSetTest extends TestCase {
  public static Test suite() {
    List<Feature<?>> allFeatures =
        Arrays.<Feature<?>>asList(
            CollectionSize.ANY,
            CollectionFeature.ALLOWS_NULL_VALUES,
            CollectionFeature.FAILS_FAST_ON_CONCURRENT_MODIFICATION,

 */
@GwtIncompatible // java.util.Arrays#copyOf(Object[], int), java.lang.reflect.Array
public class CompactHashSetTest extends TestCase {
  public static Test suite() {
    List<Feature<?>> allFeatures =
        Arrays.<Feature<?>>asList(
            CollectionSize.ANY,
            CollectionFeature.ALLOWS_NULL_VALUES,
            CollectionFeature.FAILS_FAST_ON_CONCURRENT_MODIFICATION,

    assertEquals("Three Objects should be delivered.", 3, objectEvents.size());
    assertEquals("String fixture must be first object delivered.", EVENT, objectEvents.get(0));
    assertEquals("Object fixture must be second object delivered.", objEvent, objectEvents.get(1));
    assertEquals(
        "Comparable fixture must be thirdobject delivered.", compEvent, objectEvents.get(2));

    // Check the Catcher<Comparable<?>>...