Validate packages against their SDK constraints.

utils/pub/package.dart

 // Copyright (c) 2012, 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 package;
 
 import 'dart:async';
 import 'io.dart';
 import 'pubspec.dart';
 import 'source.dart';
@@ skipping 40 matching lines @@
   }
 
   /// The package's version.
   Version get version => pubspec.version;
 
   /// The parsed pubspec associated with this package.
   final Pubspec pubspec;
 
   /// The ids of the packages that this package depends on. This is what is
   /// specified in the pubspec when this package depends on another.
-  Collection<PackageRef> get dependencies => pubspec.dependencies;
+  List<PackageRef> get dependencies => pubspec.dependencies;
 
   /// Returns the path to the README file at the root of the entrypoint, or null
   /// if no README file is found. If multiple READMEs are found, this uses the
   /// same conventions as pub.dartlang.org for choosing the primary one: the
   /// README with the fewest extensions that is lexically ordered first is
   /// chosen.
   Future<String> get readmePath {
     return listDir(dir).then((entries) {
       var readmes = entries.where((entry) => entry.contains(_README_REGEXP));
       if (readmes.isEmpty) return;
@@ skipping 45 matching lines @@
   /// by the URL "git://github.com/dart/uilib.git".
   final description;
 
   PackageId(this.name, this.source, this.version, this.description);
 
   /// Whether this ID identifies the root package.
   bool get isRoot => source == null;
 
   int get hashCode => name.hashCode ^ source.hashCode ^ version.hashCode;
 
+  /// Gets the directory where this package is or would be found in the
+  /// [SystemCache].
+  Future<String> get systemCacheDirectory => source.systemCacheDirectory(this);
+
   bool operator ==(other) {
     if (other is! PackageId) return false;
     // TODO(rnystrom): We're assuming here the name/version/source tuple is
     // enough to uniquely identify the package and that we don't need to delve
     // into the description.
     return other.name == name &&
            other.source == source &&
            other.version == version;
   }
 
@@ skipping 82 matching lines @@
 
 class PubspecNameMismatchException implements Exception {
   final String expectedName;
   final String actualName;
 
   PubspecNameMismatchException(this.expectedName, this.actualName);
 
   String toString() => 'The name you specified for your dependency, '
     '"$expectedName", doesn\'t match the name "$actualName" in its pubspec.';
 }