Listen for context add/remove and unit invalidation to update the index.

pkg/analysis_server/lib/src/services/search/search_engine_internal2.dart

 // Copyright (c) 2016, 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 services.src.search.search_engine2;
 
 import 'dart:async';
 
 import 'package:analysis_server/src/services/correction/source_range.dart';
 import 'package:analysis_server/src/services/index2/index2.dart';
 import 'package:analysis_server/src/services/search/search_engine.dart';
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/visitor.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/src/dart/element/member.dart';
 import 'package:analyzer/src/generated/engine.dart' show AnalysisContext;
 import 'package:analyzer/src/generated/resolver.dart' show NamespaceBuilder;
 import 'package:analyzer/src/generated/source.dart' show Source, SourceRange;
 import 'package:analyzer/src/summary/idl.dart';
 
 /**
  * A [SearchEngine] implementation.
  */
 class SearchEngineImpl2 implements SearchEngine {
-  final AnalysisContext context;
   final Index2 _index;
 
-  SearchEngineImpl2(this.context, this._index);
+  SearchEngineImpl2(this._index);
 
   @override
   Future<List<SearchMatch>> searchAllSubtypes(ClassElement type) async {
     List<SearchMatch> matches = <SearchMatch>[];
     await _addMatches(
         matches, type, IndexRelationKind.IS_ANCESTOR_OF, MatchKind.DECLARATION);
     return matches;
   }
 
   @override
@@ skipping 65 matching lines @@
       IndexRelationKind relationKind, MatchKind kind) async {
     List<Location> locations = await _index.getRelations(element, relationKind);
     for (Location location in locations) {
       SearchMatch match = _newMatchForLocation(location, kind);
       matches.add(match);
     }
   }
 
   SearchMatch _newMatchForLocation(Location location, MatchKind kind) =>
       new SearchMatch(
-          context,
+          location.context,
           location.libraryUri,
           location.unitUri,
           kind,
           new SourceRange(location.offset, location.length),
           true,
           location.isQualified);
 
   Future<List<SearchMatch>> _searchDefinedNames(
       String pattern, IndexNameKind nameKind) async {
     RegExp regExp = new RegExp(pattern);
@@ skipping 44 matching lines @@
     await _addMatches(matches, element, IndexRelationKind.IS_INVOKED_BY,
         MatchKind.INVOCATION);
     return matches;
   }
 
   Future<List<SearchMatch>> _searchReferences_Import(
       ImportElement element) async {
     List<SearchMatch> matches = <SearchMatch>[];
     LibraryElement libraryElement = element.library;
     Source librarySource = libraryElement.source;
+    AnalysisContext context = libraryElement.context;
     for (CompilationUnitElement unitElement in libraryElement.units) {
       Source unitSource = unitElement.source;
       CompilationUnit unit =
           context.resolveCompilationUnit2(unitSource, librarySource);
       _ImportElementReferencesVisitor visitor =
           new _ImportElementReferencesVisitor(
               element, unitSource.uri.toString());
       unit.accept(visitor);
       matches.addAll(visitor.matches);
     }
     return matches;
   }
 
   Future<List<SearchMatch>> _searchReferences_Library(Element element) async {
     List<SearchMatch> matches = <SearchMatch>[];
     LibraryElement libraryElement = element.library;
     Source librarySource = libraryElement.source;
+    AnalysisContext context = libraryElement.context;
     for (CompilationUnitElement unitElement in libraryElement.parts) {
       Source unitSource = unitElement.source;
       CompilationUnit unit =
           context.resolveCompilationUnit2(unitSource, librarySource);
       for (Directive directive in unit.directives) {
         if (directive is PartOfDirective &&
             directive.element == libraryElement) {
           matches.add(new SearchMatch(
               context,
               librarySource.uri.toString(),
@@ skipping 24 matching lines @@
     matches.addAll(await _searchReferences_Local(
         parameter, (n) => n is MethodDeclaration || n is FunctionExpression));
     return matches;
   }
 
   Future<List<SearchMatch>> _searchReferences_Prefix(
       PrefixElement element) async {
     List<SearchMatch> matches = <SearchMatch>[];
     LibraryElement libraryElement = element.library;
     Source librarySource = libraryElement.source;
+    AnalysisContext context = libraryElement.context;
     for (CompilationUnitElement unitElement in libraryElement.units) {
       Source unitSource = unitElement.source;
       CompilationUnit unit =
           context.resolveCompilationUnit2(unitSource, librarySource);
       _LocalReferencesVisitor visitor =
           new _LocalReferencesVisitor(element, unitSource.uri.toString());
       unit.accept(visitor);
       matches.addAll(visitor.matches);
     }
     return matches;
@@ skipping 111 matching lines @@
       _addMatch(node, kind);
     }
   }
 
   void _addMatch(AstNode node, MatchKind kind) {
     bool isQualified = node is SimpleIdentifier && node.isQualified;
     matches.add(new SearchMatch(context, libraryUri, unitUri, kind,
         rangeNode(node), true, isQualified));
   }
 }