Detect an expired content shell and emit a nice error.

lib/src/runner/browser/content_shell.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 test.runner.browser.content_shell;
 
 import 'dart:async';
+import 'dart:convert';
 import 'dart:io';
 
+import '../application_exception.dart';
 import 'browser.dart';
 
+/// A converter that transforms a byte stream into a stream of lines.
+final _lines = UTF8.decoder.fuse(const LineSplitter());
+
 /// A class for running an instance of the Dartium content shell.
 ///
 /// Most of the communication with the browser is expected to happen via HTTP,
 /// so this exposes a bare-bones API. The browser starts as soon as the class is
 /// constructed, and is killed when [close] is called.
 ///
 /// Any errors starting or running the process are reported through [onExit].
 class ContentShell implements Browser {
   /// The underlying process.
   Process _process;
 
   Future get onExit => _onExitCompleter.future;
   final _onExitCompleter = new Completer();
 
   /// A future that completes when the browser process has started.
   ///
   /// This is used to ensure that [close] works regardless of when it's called.
   Future get _onProcessStarted => _onProcessStartedCompleter.future;
   final _onProcessStartedCompleter = new Completer();
 
   /// Starts a new instance of content shell open to the given [url], which may
   /// be a [Uri] or a [String].
   ///
   /// If [executable] is passed, it's used as the content shell executable.
   /// Otherwise the default executable name for the current OS will be used.
   ContentShell(url, {String executable}) {
     if (executable == null) executable = _defaultExecutable();
 
+    // Whether we killed content shell because it used an expired Dart version.
+    var expired = false;
+
     // Don't return a Future here because there's no need for the caller to wait
     // for the process to actually start. They should just wait for the HTTP
     // request instead.
     Process.start(executable, ["--dump-render-tree", url.toString()],
         environment: {"DART_FLAGS": "--checked"}).then((process) {
+      _lines.bind(process.stderr).listen((line) {
+        if (line != "[dartToStderr]: Dartium build has expired") return;
+        expired = true;
+        process.kill();
+      });
+
       _process = process;
       _onProcessStartedCompleter.complete();
       return _process.exitCode;
     }).then((exitCode) {
+      if (expired) {
+        // TODO(nweiz): link to dartlang.org once it has download links for
+        // content shell
+        // (https://github.com/dart-lang/www.dartlang.org/issues/1164).
+        throw new ApplicationException(
+            "You're using an expired content_shell. Upgrade to the latest "
+                "version:\n"
+            "http://gsdview.appspot.com/dart-archive/channels/stable/release/"
+                "latest/dartium/");
+      }
+
       if (exitCode != 0) throw "Content shell failed with exit code $exitCode.";
     }).then(_onExitCompleter.complete)
         .catchError(_onExitCompleter.completeError);
   }
 
   Future close() {
     _onProcessStarted.then((_) => _process.kill());
 
     // Swallow exceptions. The user should explicitly use [onExit] for these.
     return onExit.catchError((_) {});
   }
 
   /// Return the default executable for the current operating system.
   String _defaultExecutable() =>
       Platform.isWindows ? "content_shell.exe" : "content_shell";
 }