Add on_os and on_platform fields.

lib/src/runner/configuration/load.dart

 // Copyright (c) 2016, 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.
 
 import 'dart:io';
 
 import 'package:boolean_selector/boolean_selector.dart';
 import 'package:glob/glob.dart';
 import 'package:path/path.dart' as p;
 import 'package:source_span/source_span.dart';
 import 'package:yaml/yaml.dart';
 
+import '../../backend/operating_system.dart';
 import '../../backend/platform_selector.dart';
 import '../../backend/test_platform.dart';
 import '../../frontend/timeout.dart';
 import '../../utils.dart';
+import '../../util/io.dart';
 import '../configuration.dart';
 import 'values.dart';
 
 /// Loads configuration information from a YAML file at [path].
 ///
 /// Throws a [FormatException] if the configuration is invalid, and a
 /// [FileSystemException] if it can't be read.
 Configuration load(String path) {
   var source = new File(path).readAsStringSync();
   var document = loadYamlNode(source, sourceUrl: p.toUri(path));
@@ skipping 54 matching lines @@
           (value) => value.contains(anchoredHyphenatedIdentifier));
       return tagNode.value;
     });
 
     var tags = _getMap("tags",
         key: (keyNode) => _parseNode(keyNode, "tags key",
             (value) => new BooleanSelector.parse(value)),
         value: (valueNode) =>
             _nestedConfig(valueNode, "tag value", runnerConfig: false));
 
-    return new Configuration(
+    var onPlatform = _getMap("on_platform",
+        key: (keyNode) => _parseNode(keyNode, "on_platform key",
+            (value) => new PlatformSelector.parse(value)),
+        value: (valueNode) =>
+            _nestedConfig(valueNode, "on_platform value", runnerConfig: false));
+
+    var onOS = _getMap("on_os", key: (keyNode) {
+      _validate(keyNode, "on_os key must be a string.",
+          (value) => value is String);
+
+      var os = OperatingSystem.find(keyNode.value);
+      if (os != null) return os;
+
+      throw new SourceSpanFormatException(
+          'Invalid on_os key: No such operating system.',
+          keyNode.span, _source);
+    }, value: (valueNode) => _nestedConfig(valueNode, "on_os value"));
+
+    var config = new Configuration(
         verboseTrace: verboseTrace,
         jsTrace: jsTrace,
         skip: skip,
         skipReason: skipReason,
         testOn: testOn,
         timeout: timeout,
         addTags: addTags,
-        tags: tags);
+        tags: tags,
+        onPlatform: onPlatform);
+
+    var osConfig = onOS[currentOS];
+    return osConfig == null ? config : config.merge(osConfig);
   }
 
   /// Loads runner configuration (but not test configuration).
   ///
   /// If [_runnerConfig] is `false`, this will error if there are any
   /// runner-level configuration fields.
   Configuration _loadRunnerConfig() {
     if (!_runnerConfig) {
       _disallow("reporter");
       _disallow("pub_serve");
@@ skipping 166 matching lines @@
     if (!_document.containsKey(field)) return;
     _error("$field isn't supported here.", field);
   }
 
   /// Throws a [SourceSpanFormatException] with [message] about [field].
   void _error(String message, String field) {
     throw new SourceSpanFormatException(
         message, _document.nodes[field].span, _source);
   }
 }