Safe handle removed file while incremental invalidation.

pkg/analyzer/test/src/context/context_test.dart

 // Copyright (c) 2014, 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.test.src.context.context_test;
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'package:analyzer/dart/ast/ast.dart';
@@ skipping 2860 matching lines @@
   @override
   void setUp() {
     super.setUp();
     AnalysisOptionsImpl options =
         new AnalysisOptionsImpl.from(context.analysisOptions);
     options.incremental = true;
     options.finerGrainedInvalidation = true;
     context.analysisOptions = options;
   }
 
+  void test_applyChanges_changedSource_removeFile() {
+    File file = resourceProvider.newFile('/test.dart', 'main() {}');
+    Source source = file.createSource();
+    context.applyChanges(new ChangeSet()..addedSource(source));
+    // Analyze all.
+    _performPendingAnalysisTasks();
+    expect(context.getResolvedCompilationUnit2(source, source), isNotNull);
+    // Delete the file, but tell the context that it is changed.
+    // This might happen as a race condition.
+    // Or it might be a mishandling of file notification events.
+    file.delete();
+    context.applyChanges(new ChangeSet()..changedSource(source));
+    // All the analysis results are gone.
+    void noResolvedUnits() {
+      LibrarySpecificUnit unit = new LibrarySpecificUnit(source, source);
+      RESOLVED_UNIT_RESULTS.forEach((result) {
+        expect(context.getResult(unit, result), isNull);
+      });
+    }
+
+    noResolvedUnits();
+    // Analyze again.
+    // The source does not exist, so still no resolution.
+    _performPendingAnalysisTasks();
+    noResolvedUnits();
+    expect(context.getModificationStamp(source), -1);
+  }
+
   void test_class_addMethod_useAsHole_inTopLevelVariable() {
     Source a = addSource(
         '/a.dart',
         r'''
 class A {
 }
 ''');
     Source b = addSource(
         '/b.dart',
         r'''
@@ skipping 2350 matching lines @@
    * Initialize the visitor.
    */
   _ElementGatherer();
 
   @override
   void visitElement(Element element) {
     elements[element] = element;
     super.visitElement(element);
   }
 }