Add navigation support in plugins

pkg/analyzer_plugin/lib/utilities/navigation.dart

Index: pkg/analyzer_plugin/lib/utilities/navigation.dart
diff --git a/pkg/analyzer_plugin/lib/utilities/navigation.dart b/pkg/analyzer_plugin/lib/utilities/navigation.dart
new file mode 100644
index 0000000000000000000000000000000000000000..cf0b0b4d012512196da585a98f8478309c089329
--- /dev/null
+++ b/pkg/analyzer_plugin/lib/utilities/navigation.dart
@@ -0,0 +1,85 @@
+// 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/src/dart/analysis/driver.dart';
+import 'package:analyzer_plugin/protocol/protocol.dart';
+import 'package:analyzer_plugin/protocol/protocol_common.dart'
+    show ElementKind, Location;
+import 'package:analyzer_plugin/protocol/protocol_generated.dart';
+import 'package:analyzer_plugin/src/utilities/navigation.dart';
+
+/**
+ * An object that [NavigationContributor]s use to record navigation regions.
+ *
+ * Clients may not extend, implement or mix-in this class.
+ */
+abstract class NavigationCollector {
+  /**
+   * Record a new navigation region with the given [offset] and [length] that
+   * should navigate to the given [targetLocation].
+   */
+  void addRegion(
+      int offset, int length, ElementKind targetKind, Location targetLocation);
+}
+
+/**
+ * An object used to produce navigation regions.
+ *
+ * Clients may implement this class when implementing plugins.
+ */
+abstract class NavigationContributor {
+  /**
+   * Contribute navigation regions for a subset of the content of the given
+   * [source] into the given [collector]. The subset is specified by the
+   * [offset] and [length]. The [driver] can be used to access analysis results.
+   */
+  void computeNavigation(NavigationCollector collector,
+      AnalysisDriverGeneric driver, String filePath, int offset, int length);
+}
+
+/**
+ * A generator that will generate an 'analysis.navigation' notification.
+ *
+ * Clients may not extend, implement or mix-in this class.
+ */
+class NavigationGenerator {
+  /**
+   * The driver to be passed in to the contributors.
+   */
+  final AnalysisDriverGeneric driver;
+
+  /**
+   * The contributors to be used to generate the navigation data.
+   */
+  final List<NavigationContributor> contributors;
+
+  /**
+   * Initialize a newly created navigation generator.
+   */
+  NavigationGenerator(this.driver, this.contributors);
+
+  /**
+   * Create an 'analysis.navigation' notification for the file with the given
+   * [filePath]. If any of the contributors throws an exception, also create a
+   * non-fatal 'plugin.error' notification.
+   */
+  List<Notification> generateNavigationNotification(String filePath) {
+    List<Notification> notifications = <Notification>[];
+    NavigationCollectorImpl collector = new NavigationCollectorImpl();
+    for (NavigationContributor contributor in contributors) {
+      try {
+        contributor.computeNavigation(collector, driver, filePath, null, null);
+      } catch (exception, stackTrace) {
+        notifications.add(new PluginErrorParams(
+                false, exception.toString(), stackTrace.toString())
+            .toNotification());
+      }
+    }
+    collector.createRegions();
+    notifications.add(new AnalysisNavigationParams(
+            filePath, collector.regions, collector.targets, collector.files)
+        .toNotification());
+    return notifications;
+  }
+}