* @return a new ModelSource for the resolved POM, or null if:
     *         <ul>
     *           <li>This is not a build source</li>
     *           <li>No POM can be found at the resolved location</li>
     *         </ul>
     * @throws NullPointerException if modelLocator or relative is null
     */
    @Nullable

 * encouraged to implement {@link ModelSource2} instead of implementing this interface directly.
 *
 * @see ModelSource2
 * @deprecated instead use {@link Source}
 */
@Deprecated

    }

    @Override
    public synchronized ModelSource getModelSource() {
        if (modelSource == null && pomFile != null) {
            modelSource = new FileModelSource(pomFile);
        }
        return modelSource;
    }

    @Override
    public DefaultModelBuildingRequest setModelSource(ModelSource modelSource) {
        this.modelSource = modelSource;

        return this;
    }

     * in the filesystem and support resolving related POMs.
     *
     * @param path the path to the POM file or project directory
     * @return a new ModelSource instance configured as a build source
     * @throws NullPointerException if path is null
     */
    @Nonnull
    public static ModelSource buildSource(@Nonnull Path path) {
        return new BuildPathSource(requireNonNull(path, "path"));
    }

    /**

     *
     * @see org.apache.maven.model.building.ModelSource2
     */
    ProjectBuildingResult build(ModelSource modelSource, ProjectBuildingRequest request)
            throws ProjectBuildingException;

    /**
     * Builds a project descriptor for the specified model source.
     *
     * @param modelSource The source of the model to build the project descriptor from, must not be {@code null}.

     * supports version ranges and updates the given {@code parent} instance to match the returned {@code ModelSource}.
     * If {@code parent} declares a version range, the version corresponding to the returned {@code ModelSource} will
     * be set on the given {@code parent}.
     * </p>
     *
     * @param parent The parent coordinates to resolve, must not be {@code null}.
     *

        Path basePath = Paths.get("/tmp");
        ModelSource.ModelLocator locator = mock(ModelSource.ModelLocator.class);
        Path resolvedPath = Paths.get("/tmp/subproject/pom.xml");
        when(locator.locateExistingPom(any(Path.class))).thenReturn(resolvedPath);

        Sources.BuildPathSource source = (Sources.BuildPathSource) Sources.buildSource(basePath);
        ModelSource resolved = source.resolve(locator, "subproject");

import static org.junit.jupiter.api.Assertions.assertTrue;

/**
 * Test for ModelSource interface and its implementations.
 */
class ModelSourceTest {

    @Test
    void testBuildSourceHasNoModelId() {
        Path path = Paths.get("/tmp/pom.xml");
        ModelSource source = Sources.buildSource(path);

        assertNotNull(source);

        ProjectBuildingRequest buildingRequest = request.getProjectBuildingRequest();
        ModelSource modelSource = new UrlModelSource(DefaultMaven.class.getResource("project/standalone.xml"));
        MavenProject project =
                projectBuilder.build(modelSource, buildingRequest).getProject();
        project.setExecutionRoot(true);
        request.setProjectPresent(false);

        request.setPomFile(pomFile);

        return this;
    }

    @Override
    public ModelSource getModelSource() {
        return request.getModelSource();
    }

    @Override
    public FilterModelBuildingRequest setModelSource(ModelSource modelSource) {
        request.setModelSource(modelSource);

        return this;
    }

    @Override
    public int getValidationLevel() {