ongoing.remove(new TransferResourceIdentifier(event.getResource()));
        put(event, ongoing.isEmpty());
    }

    @Override
    public void transferFailed(TransferEvent event) {
        ongoing.remove(new TransferResourceIdentifier(event.getResource()));
        put(event, ongoing.isEmpty());
    }

    private static class Exchange {
        private final TransferEvent event;

            boolean isBlankVersion = descriptor.getRequiredMavenVersion() == null
                    || descriptor.getRequiredMavenVersion().trim().isEmpty();

            if (isBlankVersion) {
                // only take value from underlying POM if plugin descriptor has no explicit Maven requirement

    public void close() {
        CompositeStoppable.stoppable(executor, cache).stop();
    }

    @Override
    public ClassPath transform(ClassPath classPath, StandardTransform transform) {
        if (classPath.isEmpty()) {
            return classPath;
        }
        return transformPipelineFor(transform).transform(classPath);

    }

    @FunctionalInterface
    private interface TransformPipeline {

                    Set<JavaAnnotation<JavaMethod>> nullableAnnotations = extractPossibleNullable(annotations);
                    if (!nullableAnnotations.isEmpty()) {

  }

  private static boolean isEmpty(Iterable<?> iterable) {
    return iterable instanceof Collection
        ? ((Collection<?>) iterable).isEmpty()
        : !iterable.iterator().hasNext();
  }

  public static void assertEmpty(Iterable<?> iterable) {
    if (!isEmpty(iterable)) {
      fail("Not true that " + iterable + " is empty");
    }
  }

    }

    @Override
    protected List<? extends DependencyMetadata> getAllDependencies() {
        List<? extends DependencyMetadata> superDependencies = super.getAllDependencies();
        if (syntheticDependencies.isEmpty()) {
            return superDependencies;
        }
        int expectedSize = superDependencies.size() + syntheticDependencies.size();

        SimpleProblemCollector problems = new SimpleProblemCollector();
        List<Profile> active = selector.getActiveProfiles(profiles, context, problems);
        assertTrue(active.isEmpty());
        assertEquals(1, problems.getErrors().size());
        assertEquals(
                "Failed to determine activation for profile one: BOOM",
                problems.getErrors().get(0));
    }

  }

  private static boolean isEmpty(Iterable<?> iterable) {
    return iterable instanceof Collection
        ? ((Collection<?>) iterable).isEmpty()
        : !iterable.iterator().hasNext();
  }

  public static void assertEmpty(Iterable<?> iterable) {
    if (!isEmpty(iterable)) {
      fail("Not true that " + iterable + " is empty");
    }
  }

    }

    @Override
    public ModuleIdentifier getId() {
        return id;
    }

    @Override
    public Collection<ComponentState> getVersions() {
        if (this.versions.isEmpty()) {
            return Collections.emptyList();
        }
        Collection<ComponentState> values = this.versions.values();
        if (areAllCandidatesForSelection(values)) {
            return values;
        }

            .filter(Optional::isPresent)
            .map(annotation -> annotation.get().name())
            .sorted()
            .collect(Collectors.toList());

        if (exposedSoftwareTypes.isEmpty()) {
            typeValidationContext.visitTypeProblem(problem ->
                problem.withAnnotationType(softwareTypePluginImplClass)