Add engine plugin

pkg/analyzer/lib/src/plugin/engine_plugin.dart

+// Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+library analyzer.src.plugin.engine_plugin;
+
+import 'package:analyzer/plugin/plugin.dart';
+import 'package:analyzer/plugin/task.dart';
+import 'package:analyzer/src/task/dart.dart';
+import 'package:analyzer/src/task/general.dart';
+import 'package:analyzer/task/model.dart';
+
+/**
+ * A plugin that defines the extension points and extensions that are inherently
+ * defined by the analysis engine.
+ */
+class EnginePlugin implements Plugin {
+  /**
+   * The simple identifier of the extension point that allows plugins to
+   * register new analysis tasks with the analysis engine.
+   */
+  static const String TASK_EXTENSION_POINT = 'task';
+
+  /**
+   * The unique identifier of this plugin.
+   */
+  static const String UNIQUE_IDENTIFIER = 'analysis_engine.core';
+
+  /**
+   * The extension point that allows plugins to register new analysis tasks with
+   * the analysis engine.
+   */
+  ExtensionPoint taskExtensionPoint;
+
+  /**
+   * Initialize a newly created plugin.
+   */
+  EnginePlugin();
+
+  /**
+   * Return a list containing all of the task descriptors that were contributed.
+   */
+  List<TaskDescriptor> taskDescriptors() {
+    return taskExtensionPoint.extensions;
+  }
+
+  @override
+  String get uniqueIdentifier => UNIQUE_IDENTIFIER;
+
+  @override
+  void registerExtensionPoints(RegisterExtensionPoint registerExtensionPoint) {
+    taskExtensionPoint =
+        registerExtensionPoint(TASK_EXTENSION_POINT, _validateTaskExtension);
+  }
+
+  @override
+  void registerExtensions(RegisterExtension registerExtension) {
+    String taskId = TASK_EXTENSION_POINT_ID;
+    //
+    // Register general tasks.
+    //
+    registerExtension(taskId, GetContentTask.DESCRIPTOR);
+    //
+    // Register Dart tasks.
+    //
+    registerExtension(taskId, BuildCompilationUnitElementTask.DESCRIPTOR);
+    registerExtension(taskId, BuildDirectiveElementsTask.DESCRIPTOR);
+    registerExtension(taskId, BuildEnumMemberElementsTask.DESCRIPTOR);
+    registerExtension(taskId, BuildExportNamespaceTask.DESCRIPTOR);
+    registerExtension(taskId, BuildExportSourceClosureTask.DESCRIPTOR);
+    registerExtension(taskId, BuildFunctionTypeAliasesTask.DESCRIPTOR);
+    registerExtension(taskId, BuildLibraryElementTask.DESCRIPTOR);
+    registerExtension(taskId, BuildPublicNamespaceTask.DESCRIPTOR);
+    registerExtension(taskId, BuildTypeProviderTask.DESCRIPTOR);
+    registerExtension(taskId, ParseDartTask.DESCRIPTOR);
+    registerExtension(taskId, ResolveTypeNamesTask.DESCRIPTOR);
+    registerExtension(taskId, ScanDartTask.DESCRIPTOR);
+    //
+    // Register HTML tasks.
+    //
+  }
+
+  /**
+   * Validate the given extension by throwing an [ExtensionError] if it is not a
+   * valid domain.
+   */
+  void _validateTaskExtension(Object extension) {
+    if (extension is! TaskDescriptor) {
+      String id = taskExtensionPoint.uniqueIdentifier;
+      throw new ExtensionError('Extensions to $id must be a TaskDescriptor');
+    }
+  }
+}