A feature should have a _source set_ with the same name.
Gradle will create a `Jar` task to bundle the classes built from the feature source set, using a classifier corresponding to the kebab-case name of the feature.

WARNING: Do not use the _main_ source set when registering a feature. This behavior will be deprecated in a future version of Gradle.

		{Name: "sha3", Feature: &ARM64.HasSHA3},
		{Name: "sha512", Feature: &ARM64.HasSHA512},
		{Name: "sm3", Feature: &ARM64.HasSM3},
		{Name: "sm4", Feature: &ARM64.HasSM4},
		{Name: "sve", Feature: &ARM64.HasSVE},
		{Name: "sve2", Feature: &ARM64.HasSVE2},
		{Name: "crc32", Feature: &ARM64.HasCRC32},
		{Name: "atomics", Feature: &ARM64.HasATOMICS},
		{Name: "asimdhp", Feature: &ARM64.HasASIMDHP},
		{Name: "cpuid", Feature: &ARM64.HasCPUID},

        when:
        def feature = createFeature("feature")

        then:
        feature.name == "feature"
        feature.sourceSet == ext.sourceSets.getByName('feature')
        feature.runtimeClasspathConfiguration == project.configurations.getByName('featureRuntimeClasspath')
        feature.compileClasspathConfiguration == project.configurations.getByName('featureCompileClasspath')

		t.Error(err)
	}
	for _, feature := range features {
		if _, ok := mandatory[feature]; ok {
			mandatory[feature] = true
		}
		if flag, ok := mapping[feature]; ok {
			if !*flag {
				t.Errorf("feature '%v' not detected", feature)
			}
		} else {
			t.Logf("no entry for '%v'", feature)
		}
	}
	for k, v := range mandatory {
		if !v {
			t.Errorf("mandatory feature '%v' not detected", k)
		}
	}

    def "can publish java-library with feature using extension"() {
        mavenRepo.module('org', 'optionaldep', '1.0').withModuleMetadata().publish()

        given:
        buildFile << """

            sourceSets {
                feature
            }

            repositories { maven { url "${mavenRepo.uri}" } }

            java {
                registerFeature("feature") {

   * @return the implied set of features
   */
  public static Set<Feature<?>> impliedFeatures(Set<Feature<?>> features) {
    Set<Feature<?>> impliedSet = new LinkedHashSet<>();
    Queue<Feature<?>> queue = new ArrayDeque<>(features);
    while (!queue.isEmpty()) {
      Feature<?> feature = queue.remove();
      for (Feature<?> implied : feature.getImpliedFeatures()) {
        if (!features.contains(implied) && impliedSet.add(implied)) {

	// initialzation, it can flip the support at runtime.
	Supports(feature storage.Feature) bool
	// CheckClient works with etcd client to recalcualte feature support and cache it internally.
	// All etcd clients should support feature to cause `Supports` return true.
	// If client A supports and client B doesn't support the feature, the `Supports` will
	// first return true at client A initializtion and then return false on client B

# Feature Coverage Reporting

## Overview

The features package defines values that are used to track feature coverage at eng.istio.io

## Labeling a Test

    Set<Feature<?>> features = Sets.<Feature<?>>newHashSet(ExampleBaseFeature.BASE_FEATURE_1);
    assertSame(features, FeatureUtil.addImpliedFeatures(features));
  }

  public void testAddImpliedFeatures_addsImpliedFeatures() throws Exception {
    Set<Feature<?>> features;

    features = Sets.<Feature<?>>newHashSet(ExampleDerivedFeature.DERIVED_FEATURE_1);

		{Name: "aesctr", Feature: &S390X.HasAESCTR},
		{Name: "aesgcm", Feature: &S390X.HasAESGCM},
		{Name: "ghash", Feature: &S390X.HasGHASH},
		{Name: "sha1", Feature: &S390X.HasSHA1},
		{Name: "sha256", Feature: &S390X.HasSHA256},
		{Name: "sha3", Feature: &S390X.HasSHA3},
		{Name: "sha512", Feature: &S390X.HasSHA512},
		{Name: "vx", Feature: &S390X.HasVX},
		{Name: "vxe", Feature: &S390X.HasVXE},
	}
}