Add debugging prints to the Mac OS directory watcher.

pkg/watcher/test/utils.dart

 // Copyright (c) 2012, 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 watcher.test.utils;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:io';
 
 import 'package:path/path.dart' as p;
 import 'package:scheduled_test/scheduled_test.dart';
 import 'package:unittest/compact_vm_config.dart';
 import 'package:watcher/watcher.dart';
 import 'package:watcher/src/stat.dart';
 import 'package:watcher/src/utils.dart';
 
+// TODO(nweiz): remove this when issue 15042 is fixed.
+import 'package:watcher/src/directory_watcher/mac_os.dart';
+
 /// The path to the temporary sandbox created for each test. All file
 /// operations are implicitly relative to this directory.
 String _sandboxDir;
 
 /// The [DirectoryWatcher] being used for the current scheduled test.
 DirectoryWatcher _watcher;
 
 /// The index in [_watcher]'s event stream for the next event. When event
 /// expectations are set using [expectEvent] (et. al.), they use this to
 /// expect a series of events in order.
@@ skipping 80 matching lines @@
 }
 
 /// The stream of events from the watcher started with [startWatcher].
 Stream _watcherEvents;
 
 /// Creates a new [DirectoryWatcher] that watches a temporary directory and
 /// starts monitoring it for events.
 ///
 /// If [dir] is provided, watches a subdirectory in the sandbox with that name.
 void startWatcher({String dir}) {
+  var testCase = currentTestCase.description;
+  if (MacOSDirectoryWatcher.logDebugInfo) {
+    print("starting watcher for $testCase");
+  }
+
   // We want to wait until we're ready *after* we subscribe to the watcher's
   // events.
   _watcher = createWatcher(dir: dir, waitForReady: false);
 
   // Schedule [_watcher.events.listen] so that the watcher doesn't start
   // watching [dir] before it exists. Expose [_watcherEvents] immediately so
   // that it can be accessed synchronously after this.
   _watcherEvents = futureStream(schedule(() {
     var allEvents = new Queue();
     var subscription = _watcher.events.listen(allEvents.add,
         onError: currentSchedule.signalError);
 
     currentSchedule.onComplete.schedule(() {
+      if (MacOSDirectoryWatcher.logDebugInfo) {
+        print("stopping watcher for $testCase");
+      }
+
       var numEvents = _nextEvent;
       subscription.cancel();
       _nextEvent = 0;
       _watcher = null;
 
       // If there are already errors, don't add this to the output and make
       // people think it might be the root cause.
       if (currentSchedule.errors.isEmpty) {
         expect(allEvents, hasLength(numEvents));
       } else {
@@ skipping 150 matching lines @@
 void withPermutations(callback(int i, int j, int k), {int limit}) {
   if (limit == null) limit = 3;
   for (var i = 0; i < limit; i++) {
     for (var j = 0; j < limit; j++) {
       for (var k = 0; k < limit; k++) {
         callback(i, j, k);
       }
     }
   }
 }