* same class realm is used to load build extensions and load mojos for extensions=true plugins.
     * </p>
     * <strong>Note:</strong> This is part of internal implementation and may be changed or removed without notice
     *
     * @since 3.3.0
     */
    public static final String KEY_EXTENSIONS_REALMS = DefaultMavenPluginManager.class.getName() + "/extensionsRealms";

// CHECKSTYLE_OFF: RegexpHeader
/**
 * <a href="https://maven.apache.org/resolver/">Maven Resolver</a> extensions for utilizing the Maven POM and Maven
 * repository metadata.
 */

        if (lookup == null) {
            return customLifecycles != null ? customLifecycles : new HashMap<>();
        }

        // Lifecycles cannot be cached as extensions might add custom lifecycles later in the execution.
        try {
            Map<String, Lifecycle> lifecycles = new HashMap<>(lookup.lookupMap(Lifecycle.class));
            for (org.apache.maven.api.Lifecycle lf : registry) {

        PomTestWrapper pom = buildPom("build-extension-inheritance/sub");
        assertEquals(3, ((List<?>) pom.getValue("build/extensions")).size());
        assertEquals("b", pom.getValue("build/extensions[1]/artifactId"));
        assertEquals("a", pom.getValue("build/extensions[2]/artifactId"));
        assertEquals("0.2", pom.getValue("build/extensions[2]/version"));

          </description>
          <type>String</type>
        </field>
        <field>
          <name>extensions</name>
          <version>4.0.0+</version>
          <description>A set of build extensions to use from this project.</description>
          <association>
            <type>Extension</type>
            <multiplicity>*</multiplicity>
          </association>
        </field>
      </fields>

  </parent>

  <artifactId>maven-api</artifactId>
  <packaging>pom</packaging>
  <name>Maven 4 API</name>
  <description>A new immutable API for Maven 4 to better manage what plugins and extensions can influence.</description>

  <modules>
    <module>maven-api-meta</module>
    <module>maven-api-di</module>
    <module>maven-api-xml</module>
    <module>maven-api-model</module>

     * <p>
     * This type registry is NOT used by Maven Core: Maven replaces it during Session creation with a type registry
     * that supports extending it (i.e. via Maven Extensions).
     * <p>
     * Important: this "static" list of types should be in-sync with core provided types.
     */
    protected ArtifactTypeRegistry getArtifactTypeRegistry() {

 */
public interface ModelBuildingListener {

    /**
     * Notifies the listener that the model has been constructed to the extent where build extensions can be processed.
     *
     * @param event The details about the event.
     */
    default void buildExtensionsAssembled(ModelBuildingEvent event) {}

            // extensionArtifacts
            Set<Artifact> extensionArtifacts = new HashSet<>();
            List<Extension> extensions =
                    project.getModel().getDelegate().getBuild().getExtensions();
            if (extensions != null) {
                for (Extension ext : extensions) {
                    String version;
                    if (ext.getVersion() == null || ext.getVersion().isEmpty()) {

 * this implementation type, ie. no hint/name.
 *
 * This leads to a second side effect in that any @Inject request for just ModelProcessor in
 * the same injector is immediately matched to this explicit binding, which means extensions
 * cannot override this binding. This is because the lookup is always short-circuited in this
 * specific situation (plain @Inject request, and plain explicit binding for the same type.)
 *