add basic constructors for PackageGraph/PackageNode

lib/src/builder/build_step.dart

@@ -15,7 +15,7 @@ abstract class BuildStep {
   /// The primary input for this build step.
   Asset get input;
 
-  // A [Logger] for this [BuildStep].
+  /// A [Logger] for this [BuildStep].
   Logger get logger;
 
   /// Checks if an [Asset] by [id] exists as an input for this [BuildStep].

lib/src/package_graph/package_graph.dart

@@ -17,6 +17,24 @@ class PackageGraph {
   PackageGraph._(this.root, Map<String, PackageNode> allPackages)
       : allPackages = new Map.unmodifiable(allPackages);
 
+  /// Creates a [PackageGraph] given the [root] [PackageNode].
+  factory PackageGraph.fromRoot(PackageNode root) {
+    final allPackages = <String, PackageNode>{
+      root.name: root,
+    };
+
+    addDeps(PackageNode package) {
+      for (var dep in package.dependencies) {
+        if (allPackages.containsKey(dep.name)) continue;
+        allPackages[dep.name] = dep;
+        addDeps(dep);
+      }
+    }
+    addDeps(root);
+
+    return new PackageGraph._(root, allPackages);
+  }
+
   /// Creates a [PackageGraph] for the package whose top level directory lives
   /// at [packagePath] (no trailing slash).
   factory PackageGraph.forPath(String packagePath) {
@@ -62,7 +80,7 @@ class PackageGraph {
         {bool isRoot: false}) {
       var name = yaml['name'];
       assert(!nodes.containsKey(name));
-      var node = new PackageNode._(
+      var node = new PackageNode(
           name, yaml['version'], type, packageLocations[name]);
       nodes[name] = node;
 
@@ -74,7 +92,7 @@ class PackageGraph {
           var pubspec = _pubspecForUri(packageLocations[name]);
           dep = addNodeAndDeps(pubspec, _dependencyType(rootDeps[name]));
         }
-        node._dependencies.add(dep);
+        node.dependencies.add(dep);
       });
 
       return node;
@@ -113,13 +131,12 @@ class PackageNode {
   final PackageDependencyType dependencyType;
 
   /// All the packages that this package directly depends on.
-  final List<PackageNode> _dependencies = [];
-  Iterable<PackageNode> get dependencies => _dependencies.toList();
+  final List<PackageNode> dependencies = [];
 
   /// The location of the current version of this package.
   final Uri location;
 
-  PackageNode._(this.name, this.version, this.dependencyType, this.location);
+  PackageNode(this.name, this.version, this.dependencyType, this.location);
 
   String toString() => '''
   $name:

test/package_graph/package_graph_test.dart

@@ -9,61 +9,76 @@ import 'package:build/build.dart';
 main() {
   PackageGraph graph;
 
-  group('forThisPackage ', () {
-    setUp(() async {
-      graph = await new PackageGraph.forThisPackage();
-    });
+  group('PackageGraph', () {
+    group('forThisPackage ', () {
+      setUp(() async {
+        graph = await new PackageGraph.forThisPackage();
+      });
 
-    test('root', () {
-      expectPkg(
-          graph.root, 'build', isNotEmpty, PackageDependencyType.Path, './');
+      test('root', () {
+        expectPkg(
+            graph.root, 'build', isNotEmpty, PackageDependencyType.Path, './');
+      });
     });
-  });
 
-  group('basic package ', () {
-    var basicPkgPath = 'test/fixtures/basic_pkg';
+    group('basic package ', () {
+      var basicPkgPath = 'test/fixtures/basic_pkg';
 
-    setUp(() async {
-      graph = await new PackageGraph.forPath(basicPkgPath);
-    });
+      setUp(() async {
+        graph = await new PackageGraph.forPath(basicPkgPath);
+      });
 
-    test('allPackages', () {
-      expect(graph.allPackages, {
-        'a': graph['a'],
-        'b': graph['b'],
-        'c': graph['c'],
-        'basic_pkg': graph['basic_pkg'],
+      test('allPackages', () {
+        expect(graph.allPackages, {
+          'a': graph['a'],
+          'b': graph['b'],
+          'c': graph['c'],
+          'basic_pkg': graph['basic_pkg'],
+        });
       });
-    });
 
-    test('root', () {
-      expectPkg(graph.root, 'basic_pkg', '1.0.0', PackageDependencyType.Path,
-          basicPkgPath, [graph['a'], graph['b'], graph['c']]);
-    });
+      test('root', () {
+        expectPkg(graph.root, 'basic_pkg', '1.0.0', PackageDependencyType.Path,
+            basicPkgPath, [graph['a'], graph['b'], graph['c']]);
+      });
 
-    test('pub dependency', () {
-      expectPkg(graph['a'], 'a', '2.0.0', PackageDependencyType.Pub,
-          '$basicPkgPath/pkg/a/', [graph['b'], graph['c']]);
-    });
+      test('pub dependency', () {
+        expectPkg(graph['a'], 'a', '2.0.0', PackageDependencyType.Pub,
+            '$basicPkgPath/pkg/a/', [graph['b'], graph['c']]);
+      });
 
-    test('git dependency', () {
-      expectPkg(graph['b'], 'b', '3.0.0', PackageDependencyType.Github,
-          '$basicPkgPath/pkg/b/', [graph['c']]);
+      test('git dependency', () {
+        expectPkg(graph['b'], 'b', '3.0.0', PackageDependencyType.Github,
+            '$basicPkgPath/pkg/b/', [graph['c']]);
+      });
+
+      test('path dependency', () {
+        expectPkg(graph['c'], 'c', '4.0.0', PackageDependencyType.Path,
+            '$basicPkgPath/pkg/c/', [graph['basic_pkg']]);
+      });
     });
 
-    test('path dependency', () {
-      expectPkg(graph['c'], 'c', '4.0.0', PackageDependencyType.Path,
-          '$basicPkgPath/pkg/c/', [graph['basic_pkg']]);
+    test('custom creation via fromRoot', () {
+      var a = new PackageNode('a', '1.0.0', PackageDependencyType.Path, null);
+      var b = new PackageNode('b', '1.0.0', PackageDependencyType.Pub, null);
+      var c = new PackageNode('c', '1.0.0', PackageDependencyType.Pub, null);
+      var d = new PackageNode('d', '1.0.0', PackageDependencyType.Pub, null);
+      a.dependencies.addAll([b, d]);
+      b.dependencies.add(c);
+      var graph = new PackageGraph.fromRoot(a);
+      expect(graph.root, a);
+      expect(graph.allPackages, {'a': a, 'b': b, 'c': c, 'd': d});
     });
-  });
 
-  test('missing pubspec throws on create', () {
-    expect(() => new PackageGraph.forPath('test/fixtures/no_pubspec'), throws);
-  });
+    test('missing pubspec throws on create', () {
+      expect(
+          () => new PackageGraph.forPath('test/fixtures/no_pubspec'), throws);
+    });
 
-  test('missing .packages file throws on create', () {
-    expect(() => new PackageGraph.forPath('test/fixtures/no_packages_file'),
-        throws);
+    test('missing .packages file throws on create', () {
+      expect(() => new PackageGraph.forPath('test/fixtures/no_packages_file'),
+          throws);
+    });
   });
 }