DefaultModelNormalizer

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 * distributed with this work for additional information
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 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
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 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.maven.model.normalization;

import javax.inject.Named;
import javax.inject.Singleton;

import java.util.ArrayList;
import java.util.Collections;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.function.Function;

import org.apache.maven.api.model.Build;
import org.apache.maven.api.model.Dependency;
import org.apache.maven.api.model.Model;
import org.apache.maven.api.model.Plugin;
import org.apache.maven.model.building.ModelBuildingRequest;
import org.apache.maven.model.building.ModelProblemCollector;
import org.apache.maven.model.merge.MavenModelMerger;

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

    private DuplicateMerger merger = new DuplicateMerger();

    @Override
    public void mergeDuplicates(
            org.apache.maven.model.Model model, ModelBuildingRequest request, ModelProblemCollector problems) {
        model.update(mergeDuplicates(model.getDelegate(), request, problems));
    }

    @Override
    public void injectDefaultValues(
            org.apache.maven.model.Model model, ModelBuildingRequest request, ModelProblemCollector problems) {
        model.update(injectDefaultValues(model.getDelegate(), request, problems));
    }

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

        Build build = model.getBuild();
        if (build != null) {
            List<Plugin> plugins = build.getPlugins();
            Map<Object, Plugin> normalized = new LinkedHashMap<>(plugins.size() * 2);

            for (Plugin plugin : plugins) {
                Object key = plugin.getKey();
                Plugin first = normalized.get(key);
                if (first != null) {
                    plugin = merger.mergePlugin(plugin, first);
                }
                normalized.put(key, plugin);
            }

            if (plugins.size() != normalized.size()) {
                builder.build(
                        Build.newBuilder(build).plugins(normalized.values()).build());
            }
        }

        /*
         * NOTE: This is primarily to keep backward-compat with Maven 2.x which did not validate that dependencies are
         * unique within a single POM. Upon multiple declarations, 2.x just kept the last one but retained the order of
         * the first occurrence. So when we're in lenient/compat mode, we have to deal with such broken POMs and mimic
         * the way 2.x works. When we're in strict mode, the removal of duplicates just saves other merging steps from
         * aftereffects and bogus error messages.
         */
        List<Dependency> dependencies = model.getDependencies();
        Map<String, Dependency> normalized = new LinkedHashMap<>(dependencies.size() * 2);

        for (Dependency dependency : dependencies) {
            normalized.put(dependency.getManagementKey(), dependency);
        }

        if (dependencies.size() != normalized.size()) {
            builder.dependencies(normalized.values());
        }

        return builder.build();
    }

    /**
     * DuplicateMerger
     */
    protected static class DuplicateMerger extends MavenModelMerger {

        public Plugin mergePlugin(Plugin target, Plugin source) {
            return super.mergePlugin(target, source, false, Collections.emptyMap());
        }
    }

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

        builder.dependencies(injectList(model.getDependencies(), this::injectDependency));
        Build build = model.getBuild();
        if (build != null) {
            Build newBuild = Build.newBuilder(build)
                    .plugins(injectList(build.getPlugins(), this::injectPlugin))
                    .build();
            builder.build(newBuild != build ? newBuild : null);
        }

        return builder.build();
    }

    private Plugin injectPlugin(Plugin p) {
        return Plugin.newBuilder(p)
                .dependencies(injectList(p.getDependencies(), this::injectDependency))
                .build();
    }

    private Dependency injectDependency(Dependency d) {
        // we cannot set this directly in the MDO due to the interactions with dependency management
        return (d.getScope() == null || d.getScope().isEmpty()) ? d.withScope("compile") : d;
    }

    /**
     * Returns a list suited for the builders, i.e. null if not modified
     */
    private <T> List<T> injectList(List<T> list, Function<T, T> modifer) {
        List<T> newList = null;
        for (int i = 0; i < list.size(); i++) {
            T oldT = list.get(i);
            T newT = modifer.apply(oldT);
            if (newT != oldT) {
                if (newList == null) {
                    newList = new ArrayList<>(list);
                }
                newList.set(i, newT);
            }
        }
        return newList;
    }
}