pkg/unittest: Add a server for serving test assets to browsers.

lib/src/util/io.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.util.io;
 
 import 'dart:async';
 import 'dart:io';
+import 'dart:mirrors';
 
 import 'package:path/path.dart' as p;
 
+import '../runner/load_exception.dart';
+
 /// The root directory of the Dart SDK.
-final String sdkDir = _computeSdkDir();
-String _computeSdkDir() => p.dirname(p.dirname(Platform.executable));
+final String sdkDir =
+    p.dirname(p.dirname(Platform.executable));
+
+/// The path to the `lib` directory of the `unittest` package.
+String libDir({String packageRoot}) {
+  var pathToIo = libraryPath(#unittest.util.io, packageRoot: packageRoot);
+  return p.dirname(p.dirname(p.dirname(pathToIo)));
+}
 
 /// Returns whether the current Dart version supports [Isolate.kill].
 final bool supportsIsolateKill = _supportsIsolateKill;
 bool get _supportsIsolateKill {
   // This isn't 100% accurate, since early 1.9 dev releases didn't support
   // Isolate.kill(), but it's very unlikely anyone will be using them.
   // TODO(nweiz): remove this when we no longer support older Dart versions.
   var path = p.join(p.dirname(p.dirname(Platform.executable)), 'version');
   return new File(path).readAsStringSync().startsWith('1.9');
 }
@@ skipping 35 matching lines @@
   }
 
   // IPv6 addresses in URLs need to be enclosed in square brackets to avoid
   // URL ambiguity with the ":" in the address.
   if (address.type == InternetAddressType.IP_V6) {
     return new Uri(scheme: "http", host: "[${address.address}]", port: port);
   }
 
   return new Uri(scheme: "http", host: address.address, port: port);
 }
+
+/// Returns the package root for a Dart entrypoint at [path].
+///
+/// If [override] is passed, that's used. If the package root doesn't exist, a
+/// [LoadException] is thrown.
+String packageRootFor(String path, [String override]) {
+  var packageRoot = override == null
+      ? p.join(p.dirname(path), 'packages')
+      : override;
+
+  if (!new Directory(packageRoot).existsSync()) {
+    throw new LoadException(path, "Directory $packageRoot does not exist.");
+  }
+
+  return packageRoot;
+}
+
+/// The library name must be globally unique, or the wrong library path may be
+/// returned.
+String libraryPath(Symbol libraryName, {String packageRoot}) {
+  var lib = currentMirrorSystem().findLibrary(libraryName);
+  if (lib.uri.scheme != 'package') return p.fromUri(lib.uri);
+
+  // TODO(nweiz): is there a way to avoid assuming this is being run next to a
+  // packages directory?.
+  if (packageRoot == null) packageRoot = p.absolute('packages');
+  return p.join(packageRoot, p.fromUri(lib.uri.path));
+}