package once

// Singleton contains a pointer to T that must be set once.
// Until the value is set all Get() calls will block.
type Singleton[T any] struct {
	v   *T
	set chan struct{}
}

// NewSingleton creates a new unset singleton.
func NewSingleton[T any]() *Singleton[T] {
	return &Singleton[T]{set: make(chan struct{}), v: nil}
}

// Get will return the singleton value.
func (s *Singleton[T]) Get() *T {
	<-s.set
	return s.v

/**
 * Denotes that a bean should be created as a singleton instance.
 * <p>
 * Singleton-scoped beans are instantiated once and reused throughout the entire
 * Maven execution. This scope should be used for stateless services or components
 * that can be safely shared across the entire build process.
 * <p>
 * Example usage:
 * <pre>
 * {@literal @}Singleton
 * public class GlobalConfiguration {
 *     // Implementation

                DependencyScope.COMPILE_ONLY.isTransitive(),
                singleton(CommonBuilds.PROJECT_PATH_MAIN, CommonBuilds.BUILD_PATH_COMPILE)));
        result.add(internalScopeManager.createDependencyScope(
                DependencyScope.TEST_RUNTIME.id(),
                DependencyScope.TEST_RUNTIME.isTransitive(),
                singleton(CommonBuilds.PROJECT_PATH_TEST, CommonBuilds.BUILD_PATH_RUNTIME)));

import javax.inject.Provider;
import javax.inject.Singleton;

import org.eclipse.aether.util.version.GenericVersionScheme;
import org.eclipse.aether.version.VersionScheme;

/**
 * Default version scheme provider: provides singleton {@link GenericVersionScheme} instance.
 *
 * @deprecated since 4.0.0, use {@code maven-api-impl} jar instead
 */
@Singleton
@Named
@Deprecated(since = "4.0.0")

 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.maven;

import javax.inject.Inject;
import javax.inject.Named;
import javax.inject.Singleton;

import java.util.Collection;
import java.util.Collections;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedHashSet;
import java.util.Set;

import java.util.List;
import java.util.Properties;

import org.apache.maven.model.Build;
import org.apache.maven.project.MavenProject;
import org.junit.jupiter.api.Test;

import static java.util.Collections.singleton;
import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertTrue;

class DefaultBuildResumptionDataRepositoryTest {

 */
package org.apache.maven.artifact.resolver;

import javax.inject.Named;
import javax.inject.Singleton;

/**
 * Artifact collector - takes a set of original artifacts and resolves the best versions to use
 * along with their metadata. No artifacts are downloaded.
 */
@Deprecated
@Named
@Singleton
public class DefaultArtifactCollector extends org.apache.maven.repository.legacy.resolver.DefaultLegacyArtifactCollector

 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.maven.project;

import javax.inject.Named;
import javax.inject.Singleton;

import org.apache.maven.impl.resolver.DefaultModelResolver;

@Named
@Singleton
@Deprecated

 * under the License.
 */
package org.apache.maven.repository.legacy;

import javax.inject.Named;
import javax.inject.Singleton;

/**
 * Wagon for testing, for protocol <code>a</code>
 *
 */
@Named("a")
@Singleton
public class WagonA extends WagonMock {
    public String[] getSupportedProtocols() {
        return new String[] {"a"};
    }

 * under the License.
 */
package org.apache.maven.repository.legacy;

import javax.inject.Named;
import javax.inject.Singleton;

/**
 * Wagon for testing, for protocols <code>b1</code> and <code>b2</code>
 *
 */
@Named("b")
@Singleton
public class WagonB extends WagonMock {
    public String[] getSupportedProtocols() {
        return new String[] {"b1", "b2"};
    }