Drain STDOUT and STDIN for Browser process (#681)

* Drain and ignore

* add changelog and pubspec

Author: grouma

CHANGELOG.md

@@ -1,3 +1,8 @@
+## 0.12.24+4
+
+* Drain browser process `stdout` and `stdin`. This resolves test flakiness, especially in Travis
+  with the `Precise` image.
+
 ## 0.12.24+3
 
 * Extend `deserializeTimeout`.

lib/src/runner/browser/browser.dart

@@ -51,6 +51,12 @@ abstract class Browser {
   Future get onExit => _onExitCompleter.future;
   final _onExitCompleter = new Completer();
 
+  Future _drainAndIgnore(Stream s) async {
+    try {
+      await s.drain();
+    } on StateError catch (_) {}
+  }
+
   /// Creates a new browser.
   ///
   /// This is intended to be called by subclasses. They pass in [startBrowser],
@@ -65,6 +71,10 @@ abstract class Browser {
       var process = await startBrowser();
       _processCompleter.complete(process);
 
+      // If we don't drain the stdout and stderr the process can hang.
+      await Future.wait(
+          [_drainAndIgnore(process.stdout), _drainAndIgnore(process.stderr)]);
+
       var exitCode = await process.exitCode;
 
       // This hack dodges an otherwise intractable race condition. When the user

pubspec.yaml

@@ -1,5 +1,5 @@
 name: test
-version: 0.12.24+3
+version: 0.12.24+4
 author: Dart Team <[email protected]>
 description: A library for writing dart unit tests.
 homepage: https://github.com/dart-lang/test