Add support for watch events and error notifications

pkg/analyzer/lib/context/context_root.dart

 // 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/generated/utilities_general.dart';
+import 'package:path/path.dart' as path;
 
 /**
  * Information about the root directory associated with an analysis context.
  *
  * Clients may not extend, implement or mix-in this class.
  */
 class ContextRoot {
   /**
    * The absolute path of the root directory containing the files to be
    * analyzed.
@@ skipping 22 matching lines @@
   @override
   bool operator ==(other) {
     if (other is ContextRoot) {
       return root == other.root &&
           _listEqual(exclude, other.exclude, (String a, String b) => a == b);
     }
     return false;
   }
 
   /**
+   * Return `true` if the file with the given [filePath] is contained within
+   * this context root. A file contained in a context root if it is within the
+   * context [root] neither explicitly excluded or within one of the excluded
+   * directories.
+   */
+  bool containsFile(String filePath) {
+    if (!path.isWithin(root, filePath)) {
+      return false;
+    }
+    for (String excluded in exclude) {
+      if (filePath == excluded || path.isWithin(excluded, filePath)) {
+        return false;
+      }
+    }
+    return true;
+  }
+
+  /**
    * Compare the lists [listA] and [listB], using [itemEqual] to compare
    * list elements.
    */
   bool _listEqual(List listA, List listB, bool itemEqual(a, b)) {
     if (listA == null) {
       return listB == null;
     }
     if (listB == null) {
       return false;
     }
     if (listA.length != listB.length) {
       return false;
     }
     for (int i = 0; i < listA.length; i++) {
       if (!itemEqual(listA[i], listB[i])) {
         return false;
       }
     }
     return true;
   }
 }