Add preliminary packages file support to dependency_grapher.

pkg/front_end/test/dependency_grapher_test.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.
 
 import 'dart:async';
 
 import 'package:front_end/compiler_options.dart';
 import 'package:front_end/dependency_grapher.dart';
 import 'package:front_end/memory_file_system.dart';
 import 'package:path/path.dart' as pathos;
@@ skipping 12 matching lines @@
       {List<String> dependencies: const [], List<String> parts: const []}) {
     var library = cycle.libraries[Uri.parse(uri)];
     expect('${library.uri}', uri);
     expect(library.dependencies.map((dep) => '${dep.uri}'),
         unorderedEquals(dependencies));
     expect(library.parts.map((part) => '$part'), unorderedEquals(parts));
     return library;
   }
 
   Future<List<LibraryCycleNode>> getCycles(Map<String, String> contents,
-      [List<String> startingPoints]) async {
+      {List<String> startingPoints, String packagesFilePath = ''}) async {
     // If no starting points given, assume the first entry in [contents] is the
     // single starting point.
     startingPoints ??= [contents.keys.first];
     var fileSystem = new MemoryFileSystem(pathos.posix, '/');
     contents.forEach((path, text) {
       fileSystem.entityForPath(path).writeAsStringSync(text);
     });
     // TODO(paulberry): implement and test other option possibilities.
     var options = new CompilerOptions()
       ..fileSystem = fileSystem
-      ..chaseDependencies = true;
+      ..chaseDependencies = true
+      ..packagesFilePath = packagesFilePath;
     var graph = await graphForProgram(
         startingPoints.map(pathos.posix.toUri).toList(), options);
     return graph.topologicallySortedCycles;
   }
 
   /// Sort the given library cycles into a deterministic order based on their
   /// URIs for easier unit testing.
   List<LibraryCycleNode> sortCycles(Iterable<LibraryCycleNode> cycles) {
     var result = cycles.toList();
     String sortKey(LibraryCycleNode node) => node.libraries.keys.join(',');
@@ skipping 21 matching lines @@
     expect(cycles[1].libraries, hasLength(1));
     checkLibrary(cycles[1], 'file:///foo.dart',
         dependencies: ['file:///bar.dart']);
   }
 
   test_multipleStartingPoints() async {
     var cycles = await getCycles({
       '/a.dart': 'import "c.dart";',
       '/b.dart': 'import "c.dart";',
       '/c.dart': ''
-    }, [
+    }, startingPoints: [
       '/a.dart',
       '/b.dart'
     ]);
     expect(cycles, hasLength(3));
     expect(cycles[0].libraries, hasLength(1));
     checkLibrary(cycles[0], 'file:///c.dart');
     // The other two cycles might be in any order, so sort them for
     // reproducibility.
     List<LibraryCycleNode> otherCycles = sortCycles(cycles.sublist(1));
     checkLibrary(otherCycles[0], 'file:///a.dart',
         dependencies: ['file:///c.dart']);
     checkLibrary(otherCycles[1], 'file:///b.dart',
         dependencies: ['file:///c.dart']);
   }
 
+  test_packages() async {
+    var cycles = await getCycles({
+      '/foo.dart': 'import "package:foo/bar.dart";',
+      '/.packages': 'foo:pkg/foo/lib\nbar:pkg/bar/lib\n',
+      '/pkg/foo/lib/bar.dart': 'import "package:bar/baz.dart";',
+      '/pkg/bar/lib/baz.dart': ''
+    }, packagesFilePath: '/.packages');
+    expect(cycles, hasLength(3));
+    expect(cycles[0].libraries, hasLength(1));
+    checkLibrary(cycles[0], 'package:bar/baz.dart');
+    expect(cycles[1].libraries, hasLength(1));
+    checkLibrary(cycles[1], 'package:foo/bar.dart',
+        dependencies: ['package:bar/baz.dart']);
+    expect(cycles[2].libraries, hasLength(1));
+    checkLibrary(cycles[2], 'file:///foo.dart',
+        dependencies: ['package:foo/bar.dart']);
+  }
+
   test_parts() async {
     var cycles = await getCycles({
       '/foo.dart': 'library foo; part "a.dart"; part "b.dart";',
       '/a.dart': 'part of foo;',
       '/b.dart': 'part of foo;'
     });
     expect(cycles, hasLength(1));
     expect(cycles[0].libraries, hasLength(1));
     checkLibrary(cycles[0], 'file:///foo.dart',
         parts: ['file:///a.dart', 'file:///b.dart']);
@@ skipping 33 matching lines @@
     expect(bar.dependencies[0], same(foo));
   }
 
   test_singleFile() async {
     var cycles = await getCycles({'/foo.dart': ''});
     expect(cycles, hasLength(1));
     expect(cycles[0].libraries, hasLength(1));
     checkLibrary(cycles[0], 'file:///foo.dart');
   }
 }