Reset Source modification stamp to -1 if it does not exist.

pkg/analyzer/lib/src/context/context.dart

 // Copyright (c) 2015, 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.src.context.context;
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'package:analyzer/instrumentation/instrumentation.dart';
@@ skipping 1754 matching lines @@
       entry.setState(CONTENT, CacheState.FLUSHED);
       try {
         TimestampedData<String> fileContents = getContents(source);
         if (fileContents.data == sourceContent) {
           int time = fileContents.modificationTime;
           for (CacheEntry entry in _entriesFor(source)) {
             entry.modificationTime = time;
           }
           return;
         }
-      } catch (e) {}
+      } catch (e) {
+        entry.modificationTime = -1;

[Brian Wilkerson, 2015/09/23 13:53:38]

Does this need to set the modification stamp for all of the entries for the
source (similar to line 1770)? If not, is the logic on line 1770 still needed?

[scheglov, 2015/09/23 15:11:27]

In theory yes, but practically we invalidate everything at the line 1812.

I'm sorry that it hard to see now because of the work-in-progress-never-finished
limiting of invalidation.

+      }
     }
     // We need to invalidate the cache.
     {
       Object delta = null;
       if (AnalysisEngine.instance.limitInvalidationInTaskModel &&
           AnalysisEngine.isDartFileName(source.fullName)) {
         // TODO(scheglov) Incorrect implementation in general.
         entry.setState(TOKEN_STREAM, CacheState.FLUSHED);
         entry.setState(PARSED_UNIT, CacheState.FLUSHED);
         List<Source> librarySources = getLibrariesContaining(source);
@@ skipping 324 matching lines @@
         new PendingFuture<T>(_context, target, computeValue);
     if (!pendingFuture.evaluate(entry)) {
       _context._pendingFutureTargets
           .putIfAbsent(target, () => <PendingFuture>[])
           .add(pendingFuture);
       scheduleComputation();
     }
     return pendingFuture.future;
   }
 }