Respect top-level @TestOn declarations.

lib/src/backend/platform_selector.dart

 // 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.
 
 library unittest.backend.platform_selector;
 
 import 'package:source_span/source_span.dart';
 
 import 'operating_system.dart';
 import 'platform_selector/ast.dart';
 import 'platform_selector/evaluator.dart';
 import 'platform_selector/parser.dart';
 import 'platform_selector/visitor.dart';
 import 'test_platform.dart';
 
 /// The set of all valid variable names.
 final _validVariables =
     new Set<String>.from(["posix", "dart-vm", "browser", "js", "blink"])
         ..addAll(TestPlatform.all.map((platform) => platform.identifier))
         ..addAll(OperatingSystem.all.map((os) => os.name));
 
 /// An expression for selecting certain platforms, including operating systems
 /// and browsers.
 ///
 /// The syntax is mostly Dart's expression syntax restricted to boolean
-/// operations. See the README for full details.
-class PlatformSelector {
-  /// The parsed AST.
-  final Node _selector;
+/// operations. See [the README][] for full details.
+///
+/// [the README]: https://github.com/dart-lang/unittest/#platform-selector-syntax

[kevmoo, 2015/03/25 08:06:55]

nit: provide a shortname for the URL so it doesn't create a long line

[nweiz, 2015/03/25 22:40:55]

I don't think there's any reason to try to shorten the name of the referent to
preserve line length when that's more dependent on the URL anyway; I don't want
to have to write "[a]" or whatever.

Long URLs in comments have always been an exception for line length
restrictions.

+abstract class PlatformSelector {
+  /// A selector that declares that a test can be run on all platforms.
+  ///
+  /// This isn't representable in the platform selector syntax but it is the
+  /// default selector.
+  static const all = const _AllPlatforms();
 
   /// Parses [selector].
   ///
   /// This will throw a [SourceSpanFormatException] if the selector is
   /// malformed or if it uses an undefined variable.
-  PlatformSelector.parse(String selector)
+  factory PlatformSelector.parse(String selector) =>
+      new _PlatformSelector.parse(selector);
+
+  /// Returns whether the selector matches the given [platform] and [os].
+  ///
+  /// [os] defaults to [OperatingSystem.none].
+  bool evaluate(TestPlatform platform, {OperatingSystem os});
+}
+
+/// The concrete implementation of a [PlatformSelector] parsed from a string.
+///
+/// This is separate from [PlatformSelector] so that [_AllPlatforms] can
+/// implement [PlatformSelector] without having to implement private members.
+class _PlatformSelector implements PlatformSelector{
+  /// The parsed AST.
+  final Node _selector;
+
+  _PlatformSelector.parse(String selector)
       : _selector = new Parser(selector).parse() {
     _selector.accept(const _VariableValidator());
   }
 
-  /// Returns whether the selector matches the given [platform] and [os].
-  ///
-  /// [os] defaults to [OperatingSystem.none].
+  _PlatformSelector(this._selector);
+
   bool evaluate(TestPlatform platform, {OperatingSystem os}) =>
       _selector.accept(new Evaluator(platform, os: os));
+
+  String toString() => _selector.toString();
+}
+
+/// A selector that matches all platforms.
+class _AllPlatforms implements PlatformSelector {
+  const _AllPlatforms();
+
+  bool evaluate(TestPlatform platform, {OperatingSystem os}) => true;
+
+  String toString() => "*";
 }
 
 /// An AST visitor that ensures that all variables are valid.
 ///
 /// This isn't done when evaluating to ensure that errors are eagerly detected,
 /// and it isn't done when parsing to avoid coupling the syntax too tightly to
 /// the semantics.
 class _VariableValidator extends RecursiveVisitor {
   const _VariableValidator();
 
   void visitVariable(VariableNode node) {
     if (_validVariables.contains(node.name)) return;
     throw new SourceSpanFormatException("Undefined variable.", node.span);
   }
 }