Fix in multi-package-resolver to support files that will be created later (graph

test/dependency_graph_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 dev_compiler.test.dependency_graph_test;
 
 import 'package:unittest/compact_vm_config.dart';
 import 'package:unittest/unittest.dart';
 
 import 'package:dev_compiler/src/checker/dart_sdk.dart'
@@ skipping 1110 matching lines @@
             |    |-- a4.dart
             |    |    |-- a10.dart
             |    |-- a5.dart (part)
             |    |-- a6.dart (part)
             |-- harmony_feature_check.js
             |-- dart_runtime.js
             |-- dart_core.js
             ''');
       });
     });
+
+    group('represented non-existing files', () {
+      test('recognize locally change between existing and not-existing', () {
+        var n = nodeOf('/foo.dart');
+        expect(n.source, isNotNull);
+        expect(n.source.exists(), isFalse);
+        var source = testUriResolver.files[new Uri.file('/foo.dart')];
+        expect(n.source, source);
+        source.contents.data = "hi";
+        source.contents.modificationTime++;
+        expect(n.source.exists(), isTrue);
+      });
+
+      test('non-existing files are tracked in dependencies', () {
+        var node = nodeOf('/foo.dart');
+        node.source.contents.data = "import 'bar.dart';";
+        rebuild(node, graph, buildNoTransitiveChange);
+        expect(node.allDeps.contains(nodeOf('/bar.dart')), isTrue);
+
+        var source = nodeOf('/bar.dart').source;
+        source.contents.data = "hi";
+        source.contents.modificationTime++;
+        results = [];
+        rebuild(node, graph, buildWithTransitiveChange);
+        expect(results, ['bar.dart', 'foo.dart']);
+      });
+    });
+
+    group('null for non-existing files', () {
+      setUp(() {
+        testUriResolver =
+            new TestUriResolver(testFiles, representNonExistingFiles: false);
+        context = new TypeResolver.fromMock(mockSdkSources, options,
+            otherResolvers: [testUriResolver]).context;
+        graph = new SourceGraph(context, new LogReporter(), options);
+      });
+
+      test('recognize locally change between existing and not-existing', () {
+        var n = nodeOf('/foo.dart');
+        expect(n.source, isNull);
+        var source = new TestSource(new Uri.file('/foo.dart'), "hi");
+        testUriResolver.files[source.uri] = source;
+        expect(n.source, isNull);
+        n.update(graph);
+        expect(n.source, source);
+        expect(n.source.exists(), isTrue);
+        expect(n.needsRebuild, isTrue);
+      });
+
+      test('non-existing files are tracked in dependencies', () {
+        var s1 =
+            new TestSource(new Uri.file('/foo.dart'), "import 'bar.dart';");
+        testUriResolver.files[s1.uri] = s1;
+        var node = nodeOf('/foo.dart');
+        rebuild(node, graph, buildNoTransitiveChange);
+        expect(node.allDeps.length, 1);
+        expect(node.allDeps.contains(nodeOf('/bar.dart')), isTrue);
+        expect(nodeOf('/bar.dart').source, isNull);
+
+        var s2 = new TestSource(new Uri.file('/bar.dart'), "hi");
+        testUriResolver.files[s2.uri] = s2;
+        results = [];
+        rebuild(node, graph, buildWithTransitiveChange);
+        expect(results, ['bar.dart', 'foo.dart']);
+      });
+    });
   });
 }
 
 expectGraph(SourceNode node, String expectation) {
   expect(printReachable(node), equalsIgnoringWhitespace(expectation));
 }
 
 nameFor(SourceNode node) => path.basename(node.uri.path);
 printReachable(SourceNode node) {
   var seen = new Set();
@@ skipping 27 matching lines @@
           ..write(e.structureChanged ? '[structure-changed] ' : ' ')
           ..write('\n');
       });
     }
   }
   helper(node);
   return sb.toString();
 }
 
 bool _same(Set a, Set b) => a.length == b.length && a.containsAll(b);