Clean up the semantics of package descriptions.

lib/src/command/cache_add.dart

 // Copyright (c) 2014, 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 pub.command.cache_add;
 
 import 'dart:async';
 
 import 'package:pub_semver/pub_semver.dart';
 
 import '../command.dart';
 import '../log.dart' as log;
-import '../package.dart';
+import '../source/hosted.dart';
 import '../utils.dart';
 
 /// Handles the `cache add` pub command.
 class CacheAddCommand extends PubCommand {
   String get name => "add";
   String get description => "Install a package.";
   String get invocation =>
       "pub cache add <package> [--version <constraint>] [--all]";
   String get docUrl => "http://dartlang.org/tools/pub/cmd/pub-cache.html";
 
@@ skipping 28 matching lines @@
         constraint = new VersionConstraint.parse(argResults["version"]);
       } on FormatException catch (error) {
         usageException(error.message);
       }
     }
 
     // TODO(rnystrom): Support installing from git too.
     var source = cache.sources["hosted"];
 
     // TODO(rnystrom): Allow specifying the server.
-    var ids = await source.getVersions(
-        new PackageRef(package, 'hosted', package));
-    var versions = ids.map((id) => id.version)
-        .where(constraint.allows).toList();
+    var ids = (await source.getVersions(HostedSource.refFor(package)))
+        .where((id) => constraint.allows(id.version))
+        .toList();
 
-    if (versions.isEmpty) {
+    if (ids.isEmpty) {
       // TODO(rnystrom): Show most recent unmatching version?
       fail("Package $package has no versions that match $constraint.");
     }
 
-    downloadVersion(version) async {
-      var id = new PackageId(package, source.name, version, package);
+    downloadVersion(id) async {
       if (cache.contains(id)) {
         // TODO(rnystrom): Include source and description if not hosted.
         // See solve_report.dart for code to harvest.
         log.message("Already cached ${id.name} ${id.version}.");
         return null;
       }
 
       // Download it.
       await source.downloadToSystemCache(id);
     }
 
     if (argResults["all"]) {
       // Install them in ascending order.
-      versions.sort();
-      await Future.forEach(versions, downloadVersion);
+      ids.sort((id1, id2) => id1.version.compareTo(id2.version));
+      await Future.forEach(ids, downloadVersion);
     } else {
       // Pick the best matching version.
-      versions.sort(Version.prioritize);
-      await downloadVersion(versions.last);
+      ids.sort((id1, id2) => Version.prioritize(id1.version, id2.version));
+      await downloadVersion(ids.last);
     }
   }
 }