Add utilities to support the outline notification

pkg/analyzer_plugin/lib/utilities/outline/outline.dart

Index: pkg/analyzer_plugin/lib/utilities/outline/outline.dart
diff --git a/pkg/analyzer_plugin/lib/utilities/outline/outline.dart b/pkg/analyzer_plugin/lib/utilities/outline/outline.dart
new file mode 100644
index 0000000000000000000000000000000000000000..8d2cddc0a92420001d94a73ca8b399129c700da4
--- /dev/null
+++ b/pkg/analyzer_plugin/lib/utilities/outline/outline.dart
@@ -0,0 +1,116 @@
+// Copyright (c) 2017, 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.
+
+import 'package:analyzer/dart/analysis/results.dart';
+import 'package:analyzer/file_system/file_system.dart';
+import 'package:analyzer_plugin/protocol/protocol.dart';
+import 'package:analyzer_plugin/protocol/protocol_common.dart'
+    hide AnalysisError;
+import 'package:analyzer_plugin/protocol/protocol_generated.dart';
+import 'package:analyzer_plugin/src/utilities/outline/outline.dart';
+import 'package:analyzer_plugin/utilities/generator.dart';
+
+/**
+ * The information about a requested set of outline information when
+ * computing outline information in a `.dart` file.
+ *
+ * Clients may not extend, implement or mix-in this class.
+ */
+abstract class DartOutlineRequest implements OutlineRequest {
+  /**
+   * The analysis result for the file for which the outline is being requested.
+   */
+  ResolveResult get result;
+}
+
+/**
+ * An object that [OutlineContributor]s use to record outline information.
+ *
+ * Invocations of the [startElement] and [endElement] methods must be paired.
+ * Any elements started (and ended) between a [startElement] and [endElement]
+ * pair are assumed to be children of the outer pair's element and as such will
+ * automatically be added as children of the outer pair's outline node.
+ *
+ * Clients may not extend, implement or mix-in this class.
+ */
+abstract class OutlineCollector {
+  /**
+   * Stop recording information about the current element.
+   */
+  void endElement();
+
+  /**
+   * Start recording information about the given [element].
+   */
+  void startElement(Element element, int offset, int length);
+}
+
+/**
+ * An object used to produce nodes in an outline.
+ *
+ * Clients may implement this class when implementing plugins.
+ */
+abstract class OutlineContributor {
+  /**
+   * Contribute outline nodes into the given [collector].
+   */
+  void computeOutline(OutlineRequest request, OutlineCollector collector);
+}
+
+/**
+ * A generator that will generate an 'analysis.outline' notification.
+ *
+ * Clients may not extend, implement or mix-in this class.
+ */
+class OutlineGenerator {
+  /**
+   * The contributors to be used to generate the outline nodes.
+   */
+  final List<OutlineContributor> contributors;
+
+  /**
+   * Initialize a newly created outline generator to use the given
+   * [contributors].
+   */
+  OutlineGenerator(this.contributors);
+
+  /**
+   * Create an 'analysis.outline' notification. If any of the contributors
+   * throws an exception, also create a non-fatal 'plugin.error' notification.
+   */
+  GeneratorResult generateOutlineNotification(OutlineRequest request) {
+    List<Notification> notifications = <Notification>[];
+    OutlineCollectorImpl collector = new OutlineCollectorImpl();
+    for (OutlineContributor contributor in contributors) {
+      try {
+        contributor.computeOutline(request, collector);
+      } catch (exception, stackTrace) {
+        notifications.add(new PluginErrorParams(
+                false, exception.toString(), stackTrace.toString())
+            .toNotification());
+      }
+    }
+    notifications.add(
+        new AnalysisOutlineParams(request.path, collector.outlines)
+            .toNotification());
+    return new GeneratorResult(null, notifications);
+  }
+}
+
+/**
+ * The information about a requested set of outline information.
+ *
+ * Clients may not extend, implement or mix-in this class.
+ */
+abstract class OutlineRequest {
+  /**
+   * Return the path of the file for which an outline is being requested.
+   */
+  String get path;
+
+  /**
+   * Return the resource provider associated with this request.
+   */
+  ResourceProvider get resourceProvider;
+}