Make "--no-packages-dir" the default.

test/descriptor/packages.dart

 // Copyright (c) 2013, 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.
 
 /// Pub-specific scheduled_test descriptors.
 import "dart:io" show File;
 import "dart:async" show Future;
 import "dart:convert" show UTF8;
 
 import 'package:package_config/packages_file.dart' as packages_file;
 import 'package:path/path.dart' as p;
+import 'package:pub_semver/pub_semver.dart';
 import 'package:scheduled_test/descriptor.dart';
 import 'package:scheduled_test/scheduled_test.dart';
 
 import '../test_pub.dart';
 
 /// Describes a `.packages` file and its contents.
 class PackagesFileDescriptor extends Descriptor {
-  // RegExp recognizing semantic version numbers.
-  static final _semverRE =
-      new RegExp(r"^(?:0|[1-9]\d*)\.(?:0|[1-9]\d*)\.(?:0|[1-9]\d*)"
-                r"(?:-[a-zA-Z\d-]+)?(?:\+[a-zA-Z\d-]+)?$");
-
   /// A map from package names to strings describing where the packages are
   /// located on disk.
   final Map<String, String> _dependencies;
 
   /// Describes a `.packages` file with the given dependencies.
   ///
   /// [dependencies] maps package names to strings describing where the packages
   /// are located on disk.
   PackagesFileDescriptor([this._dependencies]) : super('.packages');
 
   Future create([String parent]) => schedule(() {
     if (parent == null) parent = defaultRoot;
     var contents = const <int>[];
     if (_dependencies != null) {
       var mapping = <String, Uri>{};
       _dependencies.forEach((package, version) {
         var packagePath;
-        if (_semverRE.hasMatch(version)) {
-          // If it's a semver, it's a cache reference.
+        if (_isSemver(version)) {
+          // It's a cache reference.
           packagePath = p.join(cachePath, "$package-$version");
         } else {
           // Otherwise it's a path relative to the pubspec file,
           // which is also relative to the .packages file.
           packagePath = p.fromUri(version);
         }
         mapping[package] = p.toUri(p.join(packagePath, "lib", ""));
       });
       var buffer = new StringBuffer();
       packages_file.write(buffer, mapping);
@@ skipping 24 matching lines @@
     // "." due to sdk#23809.
     var base = "/a/b/c/d/e/f/g/h/i/j/k/l/m/n/o/p";
     var map = packages_file.parse(binaryContents, Uri.parse(base));
 
     for (var package in _dependencies.keys) {
       if (!map.containsKey(package)) {
         fail(".packages does not contain $package entry");
       }
 
       var description = _dependencies[package];
-      if (_semverRE.hasMatch(description)) {
+      if (_isSemver(description)) {
         if (!map[package].path.contains(description)) {
           fail(".packages of $package has incorrect version. "
                "Expected $description, found location: ${map[package]}.");
         }
       } else {
         var expected = p.normalize(p.join(p.fromUri(description), 'lib'));
         var actual = p.normalize(p.fromUri(
             p.url.relative(map[package].toString(), from: p.dirname(base))));
 
         if (expected != actual) {
           fail("Relative path: Expected $expected, found $actual");
         }
       }
     }
 
     if (map.length != _dependencies.length) {
       for (var key in map.keys) {
         if (!_dependencies.containsKey(key)) {
           fail(".packages file contains unexpected entry: $key");
         }
       }
     }
   }
 
+  /// Returns `true` if [text] is a valid semantic version number string.
+  bool _isSemver(String text) {
+    try {
+      // See if it's a semver.
+      new Version.parse(text);
+      return true;
+    } on FormatException catch (_) {
+      // Do nothing.
+    }
+    return false;
+  }
+
   String describe() => name;
 }