Class Producers

dagger-producers/main/java/dagger/producers/internal/Producers.java:41–247

Utility methods for use in generated producer code.

 * Utility methods for use in generated producer code.
 */
public final class Producers {
  /**
   * Returns a future of {@link Produced} that represents the completion (either success or failure)
   * of the given future. If the input future succeeds, then the resulting future also succeeds with
   * a successful {@code Produced}; if the input future fails, then the resulting future succeeds
   * with a failing {@code Produced}.
   *
   * <p>Cancelling the resulting future will propagate the cancellation to the input future; but
   * cancelling the input future will trigger the resulting future to succeed with a failing
   * {@code Produced}.
   */
  // TODO(beder): Document what happens with an InterruptedException after you figure out how to
  // trigger one in a test.
  public static <T> ListenableFuture<Produced<T>> createFutureProduced(ListenableFuture<T> future) {
    return catchingAsync(
        transform(future, Producers.<T>resultToProduced(), directExecutor()),
        Throwable.class,
        Producers.<T>futureFallbackForProduced(),
        directExecutor());
  }

  private static final Function<Object, Produced<Object>> RESULT_TO_PRODUCED =
      new Function<Object, Produced<Object>>() {
        @Override
        public Produced<Object> apply(Object result) {
          return Produced.successful(result);
        }
      };

  @SuppressWarnings({"unchecked", "rawtypes"}) // bivariant implementation
  private static <T> Function<T, Produced<T>> resultToProduced() {
    return (Function) RESULT_TO_PRODUCED;
  }

  private static final AsyncFunction<Throwable, Produced<Object>> FUTURE_FALLBACK_FOR_PRODUCED =
      new AsyncFunction<Throwable, Produced<Object>>() {
        @Override
        public ListenableFuture<Produced<Object>> apply(Throwable t) throws Exception {
          Produced<Object> produced = Produced.failed(t);
          return Futures.immediateFuture(produced);
        }
      };

  @SuppressWarnings({"unchecked", "rawtypes"}) // bivariant implementation
  private static <T> AsyncFunction<Throwable, Produced<T>> futureFallbackForProduced() {
    return (AsyncFunction) FUTURE_FALLBACK_FOR_PRODUCED;
  }

  /**
   * Returns a future of a {@code Set} that contains a single element: the result of the input
   * future.
   */
  public static <T> ListenableFuture<Set<T>> createFutureSingletonSet(ListenableFuture<T> future) {
    return transform(
        future,
        new Function<T, Set<T>>() {
          @Override
          public Set<T> apply(T value) {