Clean up code that locates SDK and SDK version.

utils/pub/sdk_source.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 sdk_source;
 
 import 'dart:async';
 import 'io.dart';
 import 'package.dart';
 import 'pubspec.dart';
+import 'sdk.dart' as sdk;
 import 'source.dart';
 import 'version.dart';
 
 /// A package source that uses libraries from the Dart SDK.
 class SdkSource extends Source {
   final String name = "sdk";
   final bool shouldCache = false;
 
-  /// The root directory of the Dart SDK.
-  final String _rootDir;
-
-  String get rootDir {
-    if (_rootDir != null) return _rootDir;
-    throw "Pub can't find the Dart SDK. Please set the DART_SDK environment "
-      "variable to the Dart SDK directory.";
-  }
-
-  SdkSource(this._rootDir);
-
   /// SDK packages are not individually versioned. Instead, their version is
   /// inferred from the revision number of the SDK itself.
   Future<Pubspec> describe(PackageId id) {
-    var version;
-    return readTextFile(join(rootDir, "revision")).then((revision) {
-      version = new Version.parse("0.0.0-r.${revision.trim()}");
-      // Read the pubspec for the package's dependencies.
-      return _getPackagePath(id);
-    }).then((packageDir) {
+    return _getPackagePath(id).then((packageDir) {
       // TODO(rnystrom): What if packageDir is null?
       return Package.load(id.name, packageDir, systemCache.sources);
     }).then((package) {
       // Ignore the pubspec's version, and use the SDK's.
-      return new Pubspec(id.name, version, package.pubspec.dependencies);
+      return new Pubspec(id.name, sdk.version, package.pubspec.dependencies);
     });
   }
 
   /// Since all the SDK files are already available locally, installation just
   /// involves symlinking the SDK library into the packages directory.
   Future<bool> install(PackageId id, String destPath) {
     return _getPackagePath(id).then((path) {
       if (path == null) return new Future<bool>.immediate(false);
 
       return createPackageSymlink(id.name, path, destPath).then(
           (_) => true);
     });
   }
 
-  /// Gets the path in the SDK to the directory containing package [id]. Looks
-  /// inside both "pkg" and "lib" in the SDK. Returns `null` if the package
-  /// could not be found.
+  /// Gets the path in the SDK's "pkg" directory to the directory containing
+  /// package [id]. Returns `null` if the package could not be found.
   Future<String> _getPackagePath(PackageId id) {
-    // Look in "pkg" first.
-    var pkgPath = join(rootDir, "pkg", id.description);
-    return exists(pkgPath).then((found) {
-      if (found) return new Future<String>.immediate(pkgPath);
-
-      // Not in "pkg", so try "lib".
-      // TODO(rnystrom): Get rid of this when all SDK packages are moved from
-      // "lib" to "pkg".
-      var libPath = join(rootDir, "lib", id.description);
-      return exists(libPath).then((found) => found ? libPath : null);
-    });
+    var pkgPath = join(sdk.rootDirectory, "pkg", id.description);
+    return dirExists(pkgPath).then((found) => found ? pkgPath : null);
   }
 }