Make VersionSolver source- and description-aware.

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('io.dart');
 #import('pubspec.dart');
 #import('source.dart');
 #import('source_registry.dart');
@@ skipping 98 matching lines @@
    * by the URL "git://github.com/dart/uilib.git".
    */
   final description;
 
   PackageId(this.source, this.version, this.description);
 
   /**
    * The name of the package being identified. This will be the human-friendly
    * name like "uilib".
    */
-  String get name() => source.packageName(this);
+  String get name() => source.packageName(description);
 
   int hashCode() => name.hashCode() ^
                     source.name.hashCode() ^
                     version.hashCode();
 
   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.name == source.name &&
            other.version == version;
   }
 
   String toString() => "$name $version from ${source.name}";
 
   int compareTo(Comparable other) {
     if (other is! PackageId) throw new IllegalArgumentException(other);
 
     var sourceComp = source.name.compareTo(other.source.name);
     if (sourceComp != 0) return sourceComp;
 
     var nameComp = name.compareTo(other.name);
     if (nameComp != 0) return nameComp;
 
     return version.compareTo(other.version);
   }
+
+  /**
+   * Returns the pubspec for this package.
+   */
+  Future<Pubspec> describe() => source.describe(this);
 }
 
 /**
  * A reference to a package. Unlike a [PackageId], a PackageRef may not
  * unambiguously refer to a single package. It may describe a range of allowed
  * packages.
  */
 class PackageRef {
   /**
-   * The name of the package being referenced.
-   */
-  final String name;
-
-  /**
    * The [Source] used to look up the package.
    */
   final Source source;
 
   /**
    * The allowed package versions.
    */
   final VersionConstraint constraint;
 
   /**
    * The metadata used to identify the package being referenced. The
    * interpretation of this will vary based on the [source].
    */
   final description;
 
-  PackageRef(this.name, this.source, this.constraint, this.description);
+  /**
+   * The name of the package being referenced.
+   */
+  String get name() => source.packageName(description);
+
+  PackageRef(this.source, this.constraint, this.description);
 
   String toString() => "$name $constraint from $source ($description)";
+
+  /**
+   * Returns a [PackageId] generated from this [PackageRef] with the given
+   * concrete version.
+   */
+  PackageId atVersion(Version version) =>
+    new PackageId(source, version, description);
 }