Fix test.py and tests to use an explicit --packages flag.

tools/testing/dart/test_suite.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.
 
 /**
  * Classes and methods for enumerating and preparing tests.
  *
  * This library includes:
  *
  * - Creating tests by listing all the Dart files in certain directories,
@@ skipping 952 matching lines @@
       if (pubspecYamlFile != null) {
         var result = buildSpecialPackageRoot(pubspecYamlFile);
         baseCommands.addAll(result['commands']);
         packageRoot = result['package-root'];
         if (optionsFromFile['packageRoot'] == null ||
             optionsFromFile['packageRoot'] == "") {
           optionsFromFile['packageRoot'] = packageRoot.toNativePath();
         }
       }
     }
-    if (configuration['package_root'] != null) {
-      packageRoot = new Path(configuration['package_root']);
-      optionsFromFile['packageRoot'] = packageRoot.toNativePath();
+    if (optionsFromFile['packageRoot'] == null &&
+        optionsFromFile['packages'] == null) {
+      if (configuration['package_root'] != null) {
+        packageRoot = new Path(configuration['package_root']);
+        optionsFromFile['packageRoot'] = packageRoot.toNativePath();
+      }
+      if (configuration['packages'] != null) {
+        Path packages = new Path(configuration['packages']);
+        optionsFromFile['packages'] = packages.toNativePath();
+      }
     }
-    if (configuration['packages'] != null) {
-      Path packages = new Path(configuration['packages']);
-      optionsFromFile['packages'] = packages.toNativePath();
-    }
-
     if (new CompilerConfiguration(configuration).hasCompiler &&
         expectCompileError(info)) {
       // If a compile-time error is expected, and we're testing a
       // compiler, we never need to attempt to run the program (in a
       // browser or otherwise).
       enqueueStandardTest(baseCommands, info, testName, expectations);
     } else if (TestUtils.isBrowserRuntime(configuration['runtime'])) {
       if (info.optionsFromFile['isMultiHtmlTest']) {
         // A browser multi-test has multiple expectations for one test file.
         // Find all the different sub-test expecations for one entire test file.
@@ skipping 586 matching lines @@
     args.add(filePath.toNativePath());
     if (dartOptions != null) {
       args.addAll(dartOptions);
     }
 
     return args;
   }
 
   String packagesArgument(String packageRootFromFile,
                              String packagesFromFile) {
-    if (packagesFromFile != null) {
+    if (packageRootFromFile == 'none' ||
+        packagesFromFile == 'none') {
+      return null;
+    } else if (packagesFromFile != null) {
       return '--packages=$packagesFromFile';
-    } else if (packageRootFromFile != null && packageRootFromFile != 'none') {
+    } else if (packageRootFromFile != null) {
       return '--package-root=$packageRootFromFile';
     } else {
     return null;
     }
   }
 
   /**
    * Special options for individual tests are currently specified in various
    * ways: with comments directly in test files, by using certain imports, or by
    * creating additional files in the test directories.
@@ skipping 104 matching lines @@
     for (var match in matches) {
       if (sharedOptions != null) {
         throw new Exception(
             'More than one "// SharedOptions=" line in test $filePath');
       }
       sharedOptions = match[1].split(' ').where((e) => e != '').toList();
     }
 
     matches = packageRootRegExp.allMatches(contents);
     for (var match in matches) {
-      if (packageRoot != null) {
+      if (packageRoot != null || packages != null) {
         throw new Exception(
-            'More than one "// PackageRoot=" line in test $filePath');
+            'More than one "// Package... line in test $filePath');
       }
       packageRoot = match[1];
       if (packageRoot != 'none') {
-        // PackageRoot=none means that no package-root option should be given.
+        // PackageRoot=none means that no packages or package-root option
+        // should be given. Any other value overrides package-root and
+        // removes any packages option.  Don't use with // Packages=.
         packageRoot = '${filePath.directoryPath.join(new Path(packageRoot))}';
       }
     }
 
     matches = packagesRegExp.allMatches(contents);
     for (var match in matches) {
-      if (packages != null) {
+      if (packages != null || packageRoot != null) {
         throw new Exception(
-            'More than one "// Packages=" line in test $filePath');
+            'More than one "// Package..." line in test $filePath');
       }
       packages = match[1];
       if (packages != 'none') {
-        // Packages=none means that no packages option should be given.
+        // Packages=none means that no packages or package-root option
+        // should be given. Any other value overrides packages and removes
+        // any package-root option. Don't use with // PackageRoot=.
         packages = '${filePath.directoryPath.join(new Path(packages))}';
       }
     }
 
     List<String> otherScripts = new List<String>();
     matches = otherScriptsRegExp.allMatches(contents);
     for (var match in matches) {
       otherScripts.addAll(match[1].split(' ').where((e) => e != '').toList());
     }
 
@@ skipping 731 matching lines @@
       }
       if (path.length > WINDOWS_SHORTEN_PATH_LIMIT) {
         ++shortNameCounter;
         var pathEnd = path.substring(path.length - WINDOWS_PATH_END_LENGTH);
         path = "short${shortNameCounter}_$pathEnd";
       }
     }
     return path;
   }
 }