ListChildProjects: Add limit option

Change-Id: Ied90e49cec5c9b658ad65e7a8ab45f2ec5e03948

java/com/google/gerrit/extensions/api/projects/ProjectApi.java

@@ -106,6 +106,8 @@ public interface ProjectApi {
 
   List<ProjectInfo> children(boolean recursive) throws RestApiException;
 
+  List<ProjectInfo> children(int limit) throws RestApiException;
+
   ChildProjectApi child(String name) throws RestApiException;
 
   /**
@@ -284,6 +286,11 @@ public interface ProjectApi {
       throw new NotImplementedException();
     }
 
+    @Override
+    public List<ProjectInfo> children(int limit) throws RestApiException {
+      throw new NotImplementedException();
+    }
+
     @Override
     public ChildProjectApi child(String name) throws RestApiException {
       throw new NotImplementedException();

java/com/google/gerrit/server/api/projects/ProjectApiImpl.java

@@ -484,6 +484,15 @@ public class ProjectApiImpl implements ProjectApi {
     }
   }
 
+  @Override
+  public List<ProjectInfo> children(int limit) throws RestApiException {
+    try {
+      return children.list().withLimit(limit).apply(checkExists());
+    } catch (Exception e) {
+      throw asRestApiException("Cannot list children", e);
+    }
+  }
+
   @Override
   public ChildProjectApi child(String name) throws RestApiException {
     try {

java/com/google/gerrit/server/restapi/project/ListChildProjects.java

@@ -17,6 +17,8 @@ package com.google.gerrit.server.restapi.project;
 import static java.util.stream.Collectors.toList;
 
 import com.google.gerrit.extensions.common.ProjectInfo;
+import com.google.gerrit.extensions.restapi.BadRequestException;
+import com.google.gerrit.extensions.restapi.ResourceConflictException;
 import com.google.gerrit.extensions.restapi.RestApiException;
 import com.google.gerrit.extensions.restapi.RestReadView;
 import com.google.gerrit.extensions.restapi.TopLevelResource;
@@ -37,6 +39,9 @@ public class ListChildProjects implements RestReadView<ProjectResource> {
   @Option(name = "--recursive", usage = "to list child projects recursively")
   private boolean recursive;
 
+  @Option(name = "--limit", usage = "maximum number of parents projects to list")
+  private int limit;
+
   private final PermissionBackend permissionBackend;
   private final ChildProjects childProjects;
   private final Provider<QueryProjects> queryProvider;
@@ -55,9 +60,20 @@ public class ListChildProjects implements RestReadView<ProjectResource> {
     this.recursive = recursive;
   }
 
+  public ListChildProjects withLimit(int limit) {
+    this.limit = limit;
+    return this;
+  }
+
   @Override
   public List<ProjectInfo> apply(ProjectResource rsrc)
       throws PermissionBackendException, OrmException, RestApiException {
+    if (limit < 0) {
+      throw new BadRequestException("limit must be a positive number");
+    }
+    if (recursive && limit != 0) {
+      throw new ResourceConflictException("recursive and limit options are mutually exclusive");
+    }
     rsrc.getProjectState().checkStatePermitsRead();
     if (recursive) {
       return childProjects.list(rsrc.getNameKey());
@@ -72,6 +88,7 @@ public class ListChildProjects implements RestReadView<ProjectResource> {
     return queryProvider
         .get()
         .withQuery("parent:" + parent.get())
+        .withLimit(limit)
         .apply(TopLevelResource.INSTANCE)
         .stream()
         .filter(

javatests/com/google/gerrit/acceptance/rest/project/ListChildProjectsIT.java

@@ -48,6 +48,15 @@ public class ListChildProjectsIT extends AbstractDaemonTest {
         .inOrder();
   }
 
+  @Test
+  public void listChildrenWithLimit() throws Exception {
+    Project.NameKey child1 = createProject("p1");
+    Project.NameKey child1_1 = createProject("p1.1", child1);
+    createProject("p1.2", child1);
+
+    assertThatNameList(gApi.projects().name(child1.get()).children(1)).containsExactly(child1_1);
+  }
+
   @Test
   public void listChildrenRecursively() throws Exception {
     Project.NameKey child1 = createProject("p1");