Keep cache entries for explicitly added sources.

pkg/analyzer/test/src/context/cache_test.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 test.src.task.driver_test;
 
 import 'package:analyzer/src/context/cache.dart';
 import 'package:analyzer/src/generated/engine.dart'
     show
         AnalysisContext,
@@ skipping 578 matching lines @@
     expect(entry.getState(result3), CacheState.INVALID);
     expect(entry.getState(result4), CacheState.VALID);
     expect(entry.getValue(result1), -1);
     expect(entry.getValue(result2), -2);
     expect(entry.getValue(result3), -3);
     expect(entry.getValue(result4), 444);
     // result4 is still valid, so the entry is still in the cache
     expect(cache.get(target), entry);
   }
 
+  test_setState_invalid_keepEmpty_ifExplicitlyAdded() {
+    AnalysisTarget target = new TestSource('/a.dart');
+    CacheEntry entry = new CacheEntry(target);
+    entry.explicitlyAdded = true;
+    cache.put(entry);
+    ResultDescriptor result = new ResultDescriptor('result1', -1);
+    // set results, all of them are VALID
+    entry.setValue(result, 111, TargetedResult.EMPTY_LIST);
+    expect(entry.getState(result), CacheState.VALID);
+    expect(entry.getValue(result), 111);
+    // invalidate result, keep entry
+    entry.setState(result, CacheState.INVALID);
+    expect(cache.get(target), isNotNull);
+  }
+
   test_setState_invalid_removeEmptyEntry() {
     AnalysisTarget target1 = new TestSource('/a.dart');
     AnalysisTarget target2 = new TestSource('/b.dart');
     CacheEntry entry1 = new CacheEntry(target1);
     CacheEntry entry2 = new CacheEntry(target2);
     cache.put(entry1);
     cache.put(entry2);
     ResultDescriptor result1 = new ResultDescriptor('result1', -1);
     ResultDescriptor result2 = new ResultDescriptor('result2', -2);
     ResultDescriptor result3 = new ResultDescriptor('result3', -3);
@@ skipping 498 matching lines @@
       return DeltaResult.KEEP_CONTINUE;
     }
     return DeltaResult.INVALIDATE;
   }
 }
 
 class _TestAnalysisTarget implements AnalysisTarget {
   @override
   Source get source => null;
 }