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

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

        @Override

  @J2ktIncompatible
  @GwtIncompatible // used only in GwtIncompatible tests
  private interface Merger {

    ListenableFuture<List<String>> merged(ListenableFuture<String> a, ListenableFuture<String> b);

    Merger allMerger =
        new Merger() {
          @Override
          public ListenableFuture<List<String>> merged(
              ListenableFuture<String> a, ListenableFuture<String> b) {

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]"));

    private static final String JAVA_EXECUTABLE_PATTERN_STR = "java(?:\\.exe)?";
    private static final String GRADLE_MAIN_CLASS_PATTERN_STR = "(org\\.gradle\\.[a-zA-Z]+)";
    private static final String PLAY_SERVER_PATTERN_STR = "(play\\.core\\.server\\.NettyServer)";
    private static final String JAVA_PROCESS_STACK_TRACES_MONITOR_PATTERN_STR = "(JavaProcessStackTracesMonitor\\.java)";
    private static ExecutionMode executionMode;

            }
            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);
        }

    void put(R row, C column, V value, BinaryOperator<V> merger) {
      MutableCell<R, C, V> oldCell = table.get(row, column);
      if (oldCell == null) {
        MutableCell<R, C, V> cell = new MutableCell<>(row, column, value);
        insertionOrder.add(cell);
        table.put(row, column, cell);
      } else {
        oldCell.merge(value, merger);
      }
    }