PluginExecution existing = merged.get(key);
                    if (existing != null) {
                        element = mergePluginExecution(existing, element, sourceDominant, context);
                    }
                    merged.put(key, element);
                }

                builder.executions(merged.values());
            }
        }

        @Override

import org.apache.maven.api.services.model.*;

/**
 * Handles normalization of a model.
 *
 */
@Named
@Singleton
public class DefaultModelNormalizer implements ModelNormalizer {

    private DuplicateMerger merger = new DuplicateMerger();

    @Override
    public Model mergeDuplicates(Model model, ModelBuilderRequest request, ModelProblemCollector problems) {
        Model.Builder builder = Model.newBuilder(model);

        PomTestWrapper pom = buildPom("merged-plugin-exec-goals-order/wo-plugin-mgmt/sub");

        assertEquals(5, ((List<?>) pom.getValue("build/plugins[1]/executions[1]/goals")).size());
        assertEquals("child-a", pom.getValue("build/plugins[1]/executions[1]/goals[1]"));
        assertEquals("merged", pom.getValue("build/plugins[1]/executions[1]/goals[2]"));

            }
            return result;
        }

        public void merge(org.apache.maven.repository.legacy.metadata.ArtifactMetadata metadata) {
            // not used
        }

        public void merge(ArtifactMetadata metadata) {
            // not used
        }

                        .artifactId(pluginInfo.artifactId)
                        .name(pluginInfo.name)
                        .build()))
                .build();
    }

    @Override
    protected void merge(Metadata recessive) {
        List<Plugin> recessivePlugins = recessive.getPlugins();
        List<Plugin> plugins = metadata.getPlugins();
        if (!recessivePlugins.isEmpty() || !plugins.isEmpty()) {

            versioning.latest(artifact.getBaseVersion());
        }

        metadata.versioning(versioning.build());

        return metadata.build();
    }

    @Override
    protected void merge(Metadata recessive) {
        Versioning original = metadata.getVersioning();

        Versioning.Builder versioning = Versioning.newBuilder(original);
        versioning.lastUpdated(fmt.format(timestamp));

        Source userSource = request.getUserToolchainsSource().orElse(null);
        PersistedToolchains user = readToolchains(userSource, request, problems);

        PersistedToolchains effective = toolchainsMerger.merge(user, global, false, null);

        if (hasErrors(problems)) {
            throw new ToolchainsBuilderException("Error building toolchains", problems);
        }

            // of the form:
            //
            // mvn remote-resources:process
            //
            // From the metadata stored on the server which has been created as part of a standard
            // Maven plugin deployment we will find the right PluginDescriptor from the remote
            // repository.

    @Nullable
    Object getInputLocation();

    default XmlNode merge(@Nullable XmlNode source) {
        return merge(source, (Boolean) null);
    }

    XmlNode merge(@Nullable XmlNode source, @Nullable Boolean childMergeOverride);

    /**
     * Merge recessive into dominant and return either {@code dominant}
     * with merged information or a clone of {@code recessive} if
     * {@code dominant} is {@code null}.

        Settings recessive = Settings.newBuilder()
                .pluginGroups(Arrays.asList("org.codehaus.plexus"))
                .build();

        Settings merged = SettingsUtilsV4.merge(dominant, recessive);

        List<String> pluginGroups = merged.getPluginGroups();

        assertNotNull(pluginGroups);
        assertEquals(3, pluginGroups.size());
        assertEquals("org.apache.maven.plugins", pluginGroups.get(0));