@Override
            public <T> Optional<T> lookupOptional(Class<T> type) {
                try {
                    return Optional.of(injector.getInstance(type));
                } catch (DIException e) {
                    return Optional.empty();
                }
            }

            @Override
            public <T> Optional<T> lookupOptional(Class<T> type, String name) {

                throws InvalidVersionSpecificationException {
            ArtifactSpec dep = createArtifactSpec(id, version, scope, artifact.getScope(), optional);
            return addDependency(dep);
        }

        public ArtifactSpec addDependency(String id, String version, boolean optional)
                throws InvalidVersionSpecificationException {

import java.io.File;
import java.nio.file.Path;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import java.util.Optional;
import java.util.stream.Collectors;

import org.apache.maven.api.*;
import org.apache.maven.api.services.DependencyResolver;
import org.apache.maven.api.services.DependencyResolverResult;

                        .nonRecursive()
                        .expectResult(MODULE_C),
                scenario("Selected optional project")
                        .activeOptionalProjects(MODULE_B)
                        .expectResult(MODULE_B),
                scenario("Selected missing optional project")
                        .activeOptionalProjects("non-existing-module")
                        .expectResult(

        // As a side effect it will log the optional projects that could not be resolved.
        projectSelector.getOptionalProjectsBySelectors(request, session.getAllProjects(), allOptionalSelectors);
    }

    /**
     * Check whether any of the requested optional profiles were not activated or deactivated.
     * @param session the Maven session.
     * @param profileActivation the requested optional and required profiles.
     */

package org.apache.maven.api;

import java.nio.file.Path;
import java.time.Instant;
import java.util.Collection;
import java.util.List;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.Optional;

import org.apache.maven.api.annotations.Experimental;
import org.apache.maven.api.annotations.Nonnull;
import org.apache.maven.api.annotations.Nullable;
import org.apache.maven.api.annotations.ThreadSafe;

                    Artifact artifact = node.getArtifact();

                    try {
                        if (node.filterTrail(filter)) {
                            // If it was optional and not a direct dependency,
                            // we don't add it or its children, just allow the update of the version and artifactScope
                            if (node.isChildOfRootNode() || !artifact.isOptional()) {

     *
     * @return the name of the tool option for this path type
     */
    @Nonnull
    @Override
    public Optional<String> option() {
        return Optional.ofNullable(option);
    }

    /**
     * Returns the option followed by a string representation of the given path elements.

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import java.util.Optional;
import java.util.stream.Collectors;

import org.apache.maven.artifact.handler.ArtifactHandler;
import org.apache.maven.artifact.handler.DefaultArtifactHandler;

            }

            @Nonnull
            @Override
            public Optional<Project> getProject() {
                return Optional.ofNullable(project);
            }

            @Nonnull
            @Override
            public Optional<Artifact> getRootArtifact() {
                return Optional.ofNullable(rootArtifact);
            }

            @Nonnull
            @Override