Merge parent config values with child values

ProjectLevelConfig.getWithInheritance returns a config where values
defined in the child config will replace any matching value in the
parent config.

This change adds a boolean merge parameter to
ProjectLevelConfig.getWithInheritance that will allow the caller to
generate a config where the values from the parent config are merged
with the values from the child project.

Bug: Issue 8468
Change-Id: I5edacfacb37b7ee525b7c4e5340b97a62c4dc243

gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/rest/project/ProjectLevelConfigIT.java

@@ -22,6 +22,7 @@ import com.google.gerrit.acceptance.PushOneCommit;
 import com.google.gerrit.reviewdb.client.Project;
 import com.google.gerrit.reviewdb.client.RefNames;
 import com.google.gerrit.server.project.ProjectState;
+import java.util.Arrays;
 import org.eclipse.jgit.junit.TestRepository;
 import org.eclipse.jgit.lib.Config;
 import org.junit.Before;
@@ -114,4 +115,67 @@ public class ProjectLevelConfigIT extends AbstractDaemonTest {
 
     assertThat(state.getConfig(configName).get().toText()).isEqualTo(cfg.toText());
   }
+
+  @Test
+  public void withMergedInheritance() throws Exception {
+    String configName = "test.config";
+
+    Config parentCfg = new Config();
+    parentCfg.setString("s1", null, "k1", "parentValue1");
+    parentCfg.setString("s1", null, "k2", "parentValue2");
+    parentCfg.setString("s2", "ss", "k3", "parentValue3");
+    parentCfg.setString("s2", "ss", "k4", "parentValue4");
+
+    pushFactory
+        .create(
+            db,
+            admin.getIdent(),
+            testRepo,
+            "Create Project Level Config",
+            configName,
+            parentCfg.toText())
+        .to(RefNames.REFS_CONFIG)
+        .assertOkStatus();
+
+    Project.NameKey childProject = createProject("child", project);
+    TestRepository<?> childTestRepo = cloneProject(childProject);
+    fetch(childTestRepo, RefNames.REFS_CONFIG + ":refs/heads/config");
+    childTestRepo.reset("refs/heads/config");
+
+    Config cfg = new Config();
+    cfg.setString("s1", null, "k1", "parentValue1");
+    cfg.setString("s1", null, "k2", "parentValue2");
+    cfg.setString("s2", "ss", "k3", "parentValue3");
+    cfg.setString("s2", "ss", "k4", "parentValue4");
+    cfg.setString("s1", null, "k1", "childValue1");
+    cfg.setString("s2", "ss", "k3", "childValue2");
+    cfg.setString("s3", null, "k5", "childValue3");
+    cfg.setString("s3", "ss", "k6", "childValue4");
+
+    pushFactory
+        .create(
+            db,
+            admin.getIdent(),
+            childTestRepo,
+            "Create Project Level Config",
+            configName,
+            cfg.toText())
+        .to(RefNames.REFS_CONFIG)
+        .assertOkStatus();
+
+    ProjectState state = projectCache.get(childProject);
+
+    Config expectedCfg = new Config();
+    expectedCfg.setStringList("s1", null, "k1", Arrays.asList("childValue1", "parentValue1"));
+    expectedCfg.setString("s1", null, "k2", "parentValue2");
+    expectedCfg.setStringList("s2", "ss", "k3", Arrays.asList("childValue2", "parentValue3"));
+    expectedCfg.setString("s2", "ss", "k4", "parentValue4");
+    expectedCfg.setString("s3", null, "k5", "childValue3");
+    expectedCfg.setString("s3", "ss", "k6", "childValue4");
+
+    assertThat(state.getConfig(configName).getWithInheritance(true).toText())
+        .isEqualTo(expectedCfg.toText());
+
+    assertThat(state.getConfig(configName).get().toText()).isEqualTo(cfg.toText());
+  }
 }

gerrit-server/src/main/java/com/google/gerrit/server/config/PluginConfigFactory.java

@@ -288,7 +288,32 @@ public class PluginConfigFactory implements ReloadPluginListener {
    */
   public Config getProjectPluginConfigWithInheritance(
       Project.NameKey projectName, String pluginName) throws NoSuchProjectException {
-    return getPluginConfig(projectName, pluginName).getWithInheritance();
+    return getPluginConfig(projectName, pluginName).getWithInheritance(false);
+  }
+
+  /**
+   * Returns the configuration for the specified plugin that is stored in the '{@code
+   * <plugin-name>.config}' file in the 'refs/meta/config' branch of the specified project.
+   * Parameters from the '{@code <plugin-name>.config}' of the parent project are appended to this
+   * project's '{@code <plugin-name>.config}' files.
+   *
+   * <p>E.g.: child project: [mySection "mySubsection"] myKey = childValue
+   *
+   * <p>parent project: [mySection "mySubsection"] myKey = parentValue anotherKey = someValue
+   *
+   * <p>return: [mySection "mySubsection"] myKey = childValue myKey = parentValue anotherKey =
+   * someValue
+   *
+   * @param projectName the name of the project for which the plugin configuration should be
+   *     returned
+   * @param pluginName the name of the plugin for which the configuration should be returned
+   * @return the plugin configuration from the '{@code <plugin-name>.config}' file of the specified
+   *     project with parameters from the parent projects appended to the project values
+   * @throws NoSuchProjectException thrown if the specified project does not exist
+   */
+  public Config getProjectPluginConfigWithMergedInheritance(
+      Project.NameKey projectName, String pluginName) throws NoSuchProjectException {
+    return getPluginConfig(projectName, pluginName).getWithInheritance(true);
   }
 
   /**
@@ -310,7 +335,30 @@ public class PluginConfigFactory implements ReloadPluginListener {
    */
   public Config getProjectPluginConfigWithInheritance(
       ProjectState projectState, String pluginName) {
-    return projectState.getConfig(pluginName + EXTENSION).getWithInheritance();
+    return projectState.getConfig(pluginName + EXTENSION).getWithInheritance(false);
+  }
+
+  /**
+   * Returns the configuration for the specified plugin that is stored in the '{@code
+   * <plugin-name>.config}' file in the 'refs/meta/config' branch of the specified project.
+   * Parameters from the '{@code <plugin-name>.config}' of the parent project are appended to this
+   * project's '{@code <plugin-name>.config}' files.
+   *
+   * <p>E.g.: child project: [mySection "mySubsection"] myKey = childValue
+   *
+   * <p>parent project: [mySection "mySubsection"] myKey = parentValue anotherKey = someValue
+   *
+   * <p>return: [mySection "mySubsection"] myKey = childValue myKey = parentValue anotherKey =
+   * someValue
+   *
+   * @param projectState the project for which the plugin configuration should be returned
+   * @param pluginName the name of the plugin for which the configuration should be returned
+   * @return the plugin configuration from the '{@code <plugin-name>.config}' file of the specified
+   *     project with inheriting non-set parameters from the parent projects
+   */
+  public Config getProjectPluginConfigWithMergedInheritance(
+      ProjectState projectState, String pluginName) {
+    return projectState.getConfig(pluginName + EXTENSION).getWithInheritance(true);
   }
 
   private ProjectLevelConfig getPluginConfig(Project.NameKey projectName, String pluginName)

gerrit-server/src/main/java/com/google/gerrit/server/git/ProjectLevelConfig.java

@@ -15,11 +15,14 @@
 package com.google.gerrit.server.git;
 
 import com.google.common.collect.Iterables;
+import com.google.common.collect.Streams;
 import com.google.gerrit.reviewdb.client.RefNames;
 import com.google.gerrit.server.project.ProjectState;
 import java.io.IOException;
 import java.util.Arrays;
 import java.util.Set;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
 import org.eclipse.jgit.errors.ConfigInvalidException;
 import org.eclipse.jgit.lib.CommitBuilder;
 import org.eclipse.jgit.lib.Config;
@@ -53,6 +56,22 @@ public class ProjectLevelConfig extends VersionedMetaData {
   }
 
   public Config getWithInheritance() {
+    return getWithInheritance(false);
+  }
+
+  /**
+   * Get a Config that includes the values from all parent projects.
+   *
+   * <p>Merging means that matching sections/subsection will be merged to include the values from
+   * both parent and child config.
+   *
+   * <p>No merging means that matching sections/subsections in the child project will replace the
+   * corresponding value from the parent.
+   *
+   * @param merge whether to merge parent values with child values or not.
+   * @return a combined config.
+   */
+  public Config getWithInheritance(boolean merge) {
     Config cfgWithInheritance = new Config();
     try {
       cfgWithInheritance.fromText(get().toText());
@@ -65,21 +84,41 @@ public class ProjectLevelConfig extends VersionedMetaData {
       for (String section : parentCfg.getSections()) {
         Set<String> allNames = get().getNames(section);
         for (String name : parentCfg.getNames(section)) {
+          String[] parentValues = parentCfg.getStringList(section, null, name);
           if (!allNames.contains(name)) {
+            cfgWithInheritance.setStringList(section, null, name, Arrays.asList(parentValues));
+          } else if (merge) {
             cfgWithInheritance.setStringList(
-                section, null, name, Arrays.asList(parentCfg.getStringList(section, null, name)));
+                section,
+                null,
+                name,
+                Stream.concat(
+                        Arrays.stream(cfg.getStringList(section, null, name)),
+                        Arrays.stream(parentValues))
+                    .sorted()
+                    .distinct()
+                    .collect(Collectors.toList()));
           }
         }
 
         for (String subsection : parentCfg.getSubsections(section)) {
           allNames = get().getNames(section, subsection);
           for (String name : parentCfg.getNames(section, subsection)) {
+            String[] parentValues = parentCfg.getStringList(section, subsection, name);
             if (!allNames.contains(name)) {
+              cfgWithInheritance.setStringList(
+                  section, subsection, name, Arrays.asList(parentValues));
+            } else if (merge) {
               cfgWithInheritance.setStringList(
                   section,
                   subsection,
                   name,
-                  Arrays.asList(parentCfg.getStringList(section, subsection, name)));
+                  Streams.concat(
+                          Arrays.stream(cfg.getStringList(section, subsection, name)),
+                          Arrays.stream(parentValues))
+                      .sorted()
+                      .distinct()
+                      .collect(Collectors.toList()));
             }
           }
         }