}

  public void testPresentInstances_allAbsent() {
    List<Optional<Object>> optionals = ImmutableList.of(Optional.absent(), Optional.absent());
    assertThat(Optional.presentInstances(optionals)).isEmpty();
  }

  public void testPresentInstances_somePresent() {
    List<Optional<String>> optionals =

   * Sets.cartesianProduct with those, then transforms the result to unwrap the Optionals.
   */
  private Iterable<List<Object>> buildCartesianProduct(Set<?>... sets) {
    List<Set<Optional<?>>> optionalSets = Lists.newArrayListWithExpectedSize(sets.length);
    for (Set<?> set : sets) {
      Set<Optional<?>> optionalSet =

   *
   * @since 11.0 (generics widened in 13.0)
   */
  public static <T> Iterable<T> presentInstances(
      Iterable<? extends Optional<? extends T>> optionals) {
    checkNotNull(optionals);
    return () ->
        new AbstractIterator<T>() {
          private final Iterator<? extends Optional<? extends T>> iterator =
              checkNotNull(optionals.iterator());

   *
   * @since 11.0 (generics widened in 13.0)
   */
  public static <T> Iterable<T> presentInstances(
      Iterable<? extends Optional<? extends T>> optionals) {
    checkNotNull(optionals);
    return () ->
        new AbstractIterator<T>() {
          private final Iterator<? extends Optional<? extends T>> iterator =
              checkNotNull(optionals.iterator());

   * Predicates.notNull())}, static importing as necessary.
   *
   * <p><b>Note:</b> if {@code first} is represented as an {@link Optional}, this can be
   * accomplished with {@link Optional#or(Object) first.or(second)}. That approach also allows for
   * lazy evaluation of the fallback instance, using {@link Optional#or(Supplier)
   * first.or(supplier)}.
   *

   * Predicates.notNull())}, static importing as necessary.
   *
   * <p><b>Note:</b> if {@code first} is represented as an {@link Optional}, this can be
   * accomplished with {@link Optional#or(Object) first.or(second)}. That approach also allows for
   * lazy evaluation of the fallback instance, using {@link Optional#or(Supplier)
   * first.or(supplier)}.
   *

            .add("field11", Arrays.asList("Hello"))
            .add("field12", new ArrayList<>())
            .add("field13", new HashMap<>())
            // Optionals
            .add("field26", Optional.of("World"))
            .add("field27", Optional.absent())
            // Arrays
            .add("field31", new Object[] {"!!!"})
            .add("field32", new boolean[0])
            .add("field33", new byte[0])

- Added support for CEL expressions with escaped names in the structured authentication config. Using `[...]` to access claims or user data was recommended when names contained characters that would otherwise need escaping. CEL optionals with `?` could be used where has was not applicable — for example, `claims[?"kubernetes.io"]` or `user.extra[?"domain.io/foo"]`. ([#131574](https://github.com/kubernetes/kubernetes/pull/131574), [@enj](https://github.com/enj)) [SIG API Machinery...

- Introduce support for CEL optionals (see [CEL spec proposal 246](https://github.com/google/cel-spec/wiki/proposal-246)).
  This feature will not be fully enabled until a future Kubernetes release (likely to be v1.29), but is added in v1.28 to enable

     *
     * @return an {@link Optional} containing the map of user properties, or empty if not set
     */
    @Nonnull
    Optional<Map<String, String>> userProperties();

    /**
     * Indicates whether to show the version information and exit.
     *
     * @return an {@link Optional} containing the boolean flag, or empty if not set
     */
    @Nonnull
    Optional<Boolean> showVersionAndExit();

    /**