ListPlugins: Add support for pagination with start/limit options

Feature: Issue 6499
Change-Id: I8b6e080abbe3bd7401d505f89e71271365629c6a

Documentation/rest-api-plugins.txt

@@ -84,6 +84,61 @@ List all plugins including those that are disabled.
   }
 ----
 
+Limit(n)::
+Limit the number of plugins to be included in the results.
++
+Query the first plugin in the plugin list:
++
+.Request
+----
+  GET /plugins/?n=1 HTTP/1.0
+----
++
+.Response
+----
+  HTTP/1.1 200 OK
+  Content-Disposition: attachment
+  Content-Type: application/json; charset=UTF-8
+
+  )]}'
+  {
+    "delete-project": {
+      "id": "delete-project",
+      "index_url": "plugins/delete-project/",
+      "version": "2.9-SNAPSHOT"
+    }
+  }
+----
+
+
+Skip(S)::
+Skip the given number of plugins from the beginning of the list.
++
+Query the second plugin in the plugin list:
++
+.Request
+----
+  GET /plugins/?all&n=1&S=1 HTTP/1.0
+----
++
+.Response
+----
+  HTTP/1.1 200 OK
+  Content-Disposition: attachment
+  Content-Type: application/json; charset=UTF-8
+
+  )]}'
+  {
+    "reviewers-by-blame": {
+      "id": "reviewers-by-blame",
+      "index_url": "plugins/reviewers-by-blame/",
+      "version": "2.9-SNAPSHOT",
+      "disabled": true
+    }
+  }
+----
+
+
 [[install-plugin]]
 === Install Plugin
 --

gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/api/plugin/PluginIT.java

@@ -47,35 +47,34 @@ public class PluginIT extends AbstractDaemonTest {
     assertThat(list().get()).isEmpty();
     assertThat(list().all().get()).isEmpty();
 
-    PluginApi test;
-    PluginInfo info;
-
+    PluginApi api;
     // Install all the plugins
     InstallPluginInput input = new InstallPluginInput();
     input.raw = RawInputUtil.create(JS_PLUGIN_CONTENT);
     for (String plugin : PLUGINS) {
-      test = gApi.plugins().install(plugin + ".js", input);
-      assertThat(test).isNotNull();
-      info = test.get();
+      api = gApi.plugins().install(plugin + ".js", input);
+      assertThat(api).isNotNull();
+      PluginInfo info = api.get();
       assertThat(info.id).isEqualTo(plugin);
       assertThat(info.disabled).isNull();
     }
     assertPlugins(list().get(), PLUGINS);
 
+    // With pagination
+    assertPlugins(list().start(1).limit(2).get(), PLUGINS.subList(1, 3));
+
     // Disable
-    test = gApi.plugins().name("plugin-a");
-    test.disable();
-    test = gApi.plugins().name("plugin-a");
-    info = test.get();
-    assertThat(info.disabled).isTrue();
+    api = gApi.plugins().name("plugin-a");
+    api.disable();
+    api = gApi.plugins().name("plugin-a");
+    assertThat(api.get().disabled).isTrue();
     assertPlugins(list().get(), PLUGINS.subList(1, PLUGINS.size()));
     assertPlugins(list().all().get(), PLUGINS);
 
     // Enable
-    test.enable();
-    test = gApi.plugins().name("plugin-a");
-    info = test.get();
-    assertThat(info.disabled).isNull();
+    api.enable();
+    api = gApi.plugins().name("plugin-a");
+    assertThat(api.get().disabled).isNull();
     assertPlugins(list().get(), PLUGINS);
   }
 

gerrit-extension-api/src/main/java/com/google/gerrit/extensions/api/plugins/Plugins.java

@@ -33,6 +33,8 @@ public interface Plugins {
 
   abstract class ListRequest {
     private boolean all;
+    private int limit;
+    private int start;
 
     public List<PluginInfo> get() throws RestApiException {
       Map<String, PluginInfo> map = getAsMap();
@@ -53,6 +55,24 @@ public interface Plugins {
     public boolean getAll() {
       return all;
     }
+
+    public ListRequest limit(int limit) {
+      this.limit = limit;
+      return this;
+    }
+
+    public int getLimit() {
+      return limit;
+    }
+
+    public ListRequest start(int start) {
+      this.start = start;
+      return this;
+    }
+
+    public int getStart() {
+      return start;
+    }
   }
 
   /**

gerrit-server/src/main/java/com/google/gerrit/server/api/plugins/PluginsImpl.java

@@ -61,6 +61,8 @@ public class PluginsImpl implements Plugins {
       public SortedMap<String, PluginInfo> getAsMap() throws RestApiException {
         ListPlugins list = listProvider.get();
         list.setAll(this.getAll());
+        list.setStart(this.getStart());
+        list.setLimit(this.getLimit());
         return list.apply();
       }
     };

gerrit-server/src/main/java/com/google/gerrit/server/plugins/ListPlugins.java

@@ -14,8 +14,11 @@
 
 package com.google.gerrit.server.plugins;
 
+import static java.util.Comparator.comparing;
+import static java.util.stream.Collectors.toList;
+
 import com.google.common.base.Strings;
-import com.google.common.collect.Lists;
+import com.google.common.collect.Streams;
 import com.google.gerrit.common.Nullable;
 import com.google.gerrit.common.data.GlobalCapability;
 import com.google.gerrit.extensions.annotations.RequiresCapability;
@@ -27,12 +30,11 @@ import com.google.gerrit.server.OutputFormat;
 import com.google.gson.reflect.TypeToken;
 import com.google.inject.Inject;
 import java.io.PrintWriter;
-import java.util.Collections;
-import java.util.Comparator;
 import java.util.List;
 import java.util.Map;
 import java.util.SortedMap;
 import java.util.TreeMap;
+import java.util.stream.Stream;
 import org.kohsuke.args4j.Option;
 
 /** List the installed plugins. */
@@ -41,6 +43,8 @@ public class ListPlugins implements RestReadView<TopLevelResource> {
   private final PluginLoader pluginLoader;
 
   private boolean all;
+  private int limit;
+  private int start;
 
   @Deprecated
   @Option(name = "--format", usage = "(deprecated) output format")
@@ -55,6 +59,26 @@ public class ListPlugins implements RestReadView<TopLevelResource> {
     this.all = all;
   }
 
+  @Option(
+    name = "--limit",
+    aliases = {"-n"},
+    metaVar = "CNT",
+    usage = "maximum number of plugins to list"
+  )
+  public void setLimit(int limit) {
+    this.limit = limit;
+  }
+
+  @Option(
+    name = "--start",
+    aliases = {"-S"},
+    metaVar = "CNT",
+    usage = "number of plugins to skip"
+  )
+  public void setStart(int start) {
+    this.start = start;
+  }
+
   @Inject
   protected ListPlugins(PluginLoader pluginLoader) {
     this.pluginLoader = pluginLoader;
@@ -82,15 +106,15 @@ public class ListPlugins implements RestReadView<TopLevelResource> {
 
   public SortedMap<String, PluginInfo> display(@Nullable PrintWriter stdout) {
     SortedMap<String, PluginInfo> output = new TreeMap<>();
-    List<Plugin> plugins = Lists.newArrayList(pluginLoader.getPlugins(all));
-    Collections.sort(
-        plugins,
-        new Comparator<Plugin>() {
-          @Override
-          public int compare(Plugin a, Plugin b) {
-            return a.getName().compareTo(b.getName());
+    Stream<Plugin> s =
+        Streams.stream(pluginLoader.getPlugins(all)).sorted(comparing(Plugin::getName));
+    if (start > 0) {
+      s = s.skip(start);
     }
-        });
+    if (limit > 0) {
+      s = s.limit(limit);
+    }
+    List<Plugin> plugins = s.collect(toList());
 
     if (!format.isJson()) {
       stdout.format("%-30s %-10s %-8s %s\n", "Name", "Version", "Status", "File");