Don't extract the name of a package from its description.

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');
 #import('version.dart');
 
 /**
  * A named, versioned, unit of code and resource reuse.
  */
 class Package {
   /**
-   * Loads the package whose root directory is [packageDir].
+   * Loads the package whose root directory is [packageDir]. [name] is the
+   * expected name of that package (e.g. the name given in the dependency), or
+   * null if the package being loaded is the entrypoint package.
    */
-  static Future<Package> load(String packageDir, SourceRegistry sources) {
+  static Future<Package> load(String name, String packageDir,
+      SourceRegistry sources) {
     var pubspecPath = join(packageDir, 'pubspec.yaml');
 
     return fileExists(pubspecPath).chain((exists) {
-      if (exists) {
-        return readTextFile(pubspecPath).transform((contents) {
-          return new Pubspec.parse(contents, sources);
-        });
-      } else {
-        // If there is no pubspec, we implicitly treat that as a package with
-        // no dependencies.
-        return new Future.immediate(new Pubspec.empty());
+      if (!exists) throw new PubspecNotFoundException(name);
+      return readTextFile(pubspecPath);
+    }).transform((contents) {
+      var pubspec = new Pubspec.parse(contents, sources);
+      if (pubspec.name == null) throw new PubspecHasNoNameException(name);
+      if (name != null && pubspec.name != name) {
+        throw new PubspecNameMismatchException(name, pubspec.name);
       }
-    }).transform((pubspec) {
       return new Package._(packageDir, pubspec);
     });
   }
 
   /**
    * The path to the directory containing the package.
    */
   final String dir;
 
   /**
@@ skipping 43 matching lines @@
 /**
  * An unambiguous resolved reference to a package. A package ID contains enough
  * information to correctly install the package.
  *
  * Note that it's possible for multiple distinct package IDs to point to
  * different directories that happen to contain identical packages. For example,
  * the same package may be available from multiple sources. As far as Pub is
  * concerned, those packages are different.
  */
 class PackageId implements Comparable, Hashable {
+  /// The name of the package being identified.
+  final String name;
+
   /**
    * The [Source] used to look up this package given its [description].
    */
   final Source source;
 
   /**
    * The package's version.
    */
   final Version version;
 
   /**
    * The metadata used by the package's [source] to identify and locate it. It
    * contains whatever [Source]-specific data it needs to be able to install
    * the package. For example, the description of a git sourced package might
    * 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(description);
+  PackageId(this.name, this.source, this.version, this.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.
@@ skipping 26 matching lines @@
    */
   Future<PackageId> get resolved => source.resolveId(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 identified.
+  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;
 
-  /**
-   * The name of the package being referenced.
-   */
-  String get name => source.packageName(description);
-
-  PackageRef(this.source, this.constraint, this.description);
+  PackageRef(this.name, 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);
+    new PackageId(name, source, version, description);
 }
+
+class PubspecNotFoundException implements Exception {
+  final String name;
+
+  PubspecNotFoundException(this.name);
+
+  String toString() => 'Package "$name" doesn\'t have a pubspec.yaml file.';
+}
+
+class PubspecHasNoNameException implements Exception {
+  final String name;
+
+  PubspecHasNoNameException(this.name);
+
+  String toString() => 'Package "$name"\'s pubspec.yaml file is missing the '
+    'required "name" field (e.g. "name: $name").';
+}
+
+class PubspecNameMismatchException implements Exception {
+  final String expectedName;
+  final String actualName;
+
+  PubspecNameMismatchException(this.expectedName, this.actualName);
+
+  String toString() => 'The name you specified for your dependency, '
+    '"$expectedName", doesn\'t match the name "$actualName" in its pubspec.';
+}