Separate out VM dependencies.

The Packages interface class should not depend on a platform specific
library (dart:io).
This removed the dependency, and also splits the implementation
classes into those that are generally applicable and those that
requite dart:io to operate (the "local packages directory" which
allows iterating the package names by scanning the directory).

Bump version to 0.0.2+4

lib/discovery.dart

@@ -11,6 +11,7 @@ import "package:http/http.dart" as http;
 import "packages.dart";
 import "packages_file.dart" as pkgfile show parse;
 import "src/packages_impl.dart";
+import "src/packages_io_impl.dart";
 
 /// Discover the package configuration for a Dart script.
 ///

lib/packages.dart

@@ -4,8 +4,6 @@
 
 library package_config.packages;
 
-import "dart:async" show Future;
-import "discovery.dart" show findPackages;
 import "src/packages_impl.dart";
 
 /// A package resolution strategy.
@@ -26,42 +24,6 @@ abstract class Packages {
   /// package resolution strategy is found.
   static const Packages noPackages = const NoPackages();
 
-  /// Create a `Packages` object based on a map from package name to base URI.
-  ///
-  /// The resulting `Packages` object will resolve package URIs by using this
-  /// map.
-  /// There is no validation of the map containing only valid package names,
-  factory Packages(Map<String, Uri> packageMapping) =>
-      new MapPackages(packageMapping);
-
-  /// Attempts to find a package resolution strategy for a Dart script.
-  ///
-  /// The [baseLocation] should point to a Dart script or to its directory.
-  /// The function goes through the following steps in order to search for
-  /// a packages resolution strategy:
-  ///
-  /// * First check if a `.packages` file in the script's directory.
-  ///   If a file is found, its content is loaded and interpreted as a map
-  ///   from package names to package location URIs.
-  ///   If loading or parsing of the file fails, so does this function.
-  /// * Then if `baseLocation` is not a `file:` URI,
-  ///   assume that a `packages/` directory exists in the script's directory,
-  ///   and return a `Packages` object that resolves package URIs as
-  ///   paths into that directory.
-  /// * If `baseLocation` is a `file:` URI, instead *check* whether
-  ///   a `packages/` directory exists in the script directory.
-  ///   If it does, return a `Packages` object that resolves package URIs
-  ///   as paths into that directory. This `Packages` object is able to
-  ///   read the directory and see which packages are available.
-  /// * Otherwise, check each directory in the parent path of `baseLocation`
-  ///   for the existence of a `.packages` file. If one is found, it is loaded
-  ///   just as in the first step.
-  /// * If no file is found before reaching the file system root,
-  ///   the constant [noPackages] is returned. It's a `Packages` object
-  ///   with no available packages.
-  ///
-  static Future<Packages> find(Uri baseLocation) => findPackages(baseLocation);
-
   /// Resolve a package URI into a non-package URI.
   ///
   /// Translates a `package:` URI, according to the package resolution

lib/src/packages_impl.dart

@@ -2,11 +2,12 @@
 // 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.
 
+/// Implementations of [Packages] that may be used in either server or browser
+/// based applications. For implementations that can only run in the browser,
+/// see [package_config.packages_io_impl].
 library package_config.packages_impl;
 
 import "dart:collection" show UnmodifiableMapView;
-import "dart:io" show Directory;
-import "package:path/path.dart" as path;
 import "../packages.dart";
 import "util.dart" show checkValidPackageUri;
 
@@ -26,16 +27,15 @@ class NoPackages implements Packages {
   Map<String, Uri> asMap() => const<String,Uri>{};
 }
 
-
 /// Base class for [Packages] implementations.
 ///
 /// This class implements the [resolve] method in terms of a private
 /// member
-abstract class _PackagesBase implements Packages {
+abstract class PackagesBase implements Packages {
   Uri resolve(Uri packageUri, {Uri notFound(Uri packageUri)}) {
     packageUri = _normalizePath(packageUri);
     String packageName = checkValidPackageUri(packageUri);
-    Uri packageBase = _getBase(packageName);
+    Uri packageBase = getBase(packageName);
     if (packageBase == null) {
       if (notFound != null) return notFound(packageUri);
       throw new ArgumentError.value(packageUri, "packageUri",
@@ -49,61 +49,34 @@ abstract class _PackagesBase implements Packages {
   ///
   /// Returns `null` if no package exists with that name, and that can be
   /// determined.
-  Uri _getBase(String packageName);
+  Uri getBase(String packageName);
 
   // TODO: inline to uri.normalizePath() when we move to 1.11
   static Uri _normalizePath(Uri uri) => new Uri().resolveUri(uri);
 }
 
 /// A [Packages] implementation based on an existing map.
-class MapPackages extends _PackagesBase {
+class MapPackages extends PackagesBase {
   final Map<String, Uri> _mapping;
   MapPackages(this._mapping);
 
-  Uri _getBase(String packageName) => _mapping[packageName];
+  Uri getBase(String packageName) => _mapping[packageName];
 
   Iterable<String> get packages => _mapping.keys;
 
   Map<String, Uri> asMap() => new UnmodifiableMapView<String, Uri>(_mapping);
 }
 
-/// A [Packages] implementation based on a local directory.
-class FilePackagesDirectoryPackages extends _PackagesBase {
-  final Directory _packageDir;
-  FilePackagesDirectoryPackages(this._packageDir);
-
-  Uri _getBase(String packageName) =>
-      new Uri.file(path.join(_packageDir.path, packageName, '.'));
-
-  Iterable<String> _listPackageNames() {
-    return _packageDir.listSync()
-                      .where((e) => e is Directory)
-                      .map((e) => path.basename(e.path));
-  }
-
-  Iterable<String> get packages {
-    return _listPackageNames();
-  }
-
-  Map<String, Uri> asMap() {
-    var result = <String, Uri>{};
-    for (var packageName in _listPackageNames()) {
-      result[packageName] = _getBase(packageName);
-    }
-    return new UnmodifiableMapView<String, Uri>(result);
-  }
-}
-
 /// A [Packages] implementation based on a remote (e.g., HTTP) directory.
 ///
 /// There is no way to detect which packages exist short of trying to use
 /// them. You can't necessarily check whether a directory exists,
 /// except by checking for a know file in the directory.
-class NonFilePackagesDirectoryPackages extends _PackagesBase {
+class NonFilePackagesDirectoryPackages extends PackagesBase {
   final Uri _packageBase;
   NonFilePackagesDirectoryPackages(this._packageBase);
 
-  Uri _getBase(String packageName) => _packageBase.resolve("$packageName/");
+  Uri getBase(String packageName) => _packageBase.resolve("$packageName/");
 
   Error _failListingPackages() {
     return new UnsupportedError(

lib/src/packages_io_impl.dart

@@ -0,0 +1,37 @@
+// Copyright (c) 2015, 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.
+
+/// Implementations of [Packages] that can only be used in server based
+/// applications.
+library package_config.packages_io_impl;
+
+import "dart:collection" show UnmodifiableMapView;
+import "dart:io" show Directory;
+import "package:path/path.dart" as path;
+import "packages_impl.dart";
+
+/// A [Packages] implementation based on a local directory.
+class FilePackagesDirectoryPackages extends PackagesBase {
+  final Directory _packageDir;
+  FilePackagesDirectoryPackages(this._packageDir);
+
+  Uri getBase(String packageName) =>
+    new Uri.file(path.join(_packageDir.path, packageName, '.'));
+
+  Iterable<String> _listPackageNames() {
+    return _packageDir.listSync()
+    .where((e) => e is Directory)
+    .map((e) => path.basename(e.path));
+  }
+
+  Iterable<String> get packages => _listPackageNames();
+
+  Map<String, Uri> asMap() {
+    var result = <String, Uri>{};
+    for (var packageName in _listPackageNames()) {
+      result[packageName] = getBase(packageName);
+    }
+    return new UnmodifiableMapView<String, Uri>(result);
+  }
+}

pubspec.yaml

@@ -1,5 +1,5 @@
 name: package_config
-version: 0.0.2+4
+version: 0.0.3
 description: Support for working with Package Resolution config files.
 author: Dart Team <misc@dartlang.org>
 homepage: https://github.com/dart-lang/package_config

test/parse_test.dart

@@ -6,6 +6,7 @@ library test_all;
 
 import "package:package_config/packages.dart";
 import "package:package_config/packages_file.dart" show parse;
+import "package:package_config/src/packages_impl.dart";
 import "package:test/test.dart";
 
 main() {
@@ -123,7 +124,7 @@ main() {
 
 Packages doParse(String sample, Uri baseUri) {
   Map<String, Uri> map = parse(sample.codeUnits, baseUri);
-  return new Packages(map);
+  return new MapPackages(map);
 }
 
 // Valid samples.