Refactor Future constructors.

utils/tests/pub/test_pub.dart

 // Copyright (c) 2013, 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.
 
 /// Test infrastructure for testing pub. Unlike typical unit tests, most pub
 /// tests are integration tests that stage some stuff on the file system, run
 /// pub, and then validate the results. This library provides an API to build
 /// tests like that.
 library test_pub;
 
@@ skipping 101 matching lines @@
         currentSchedule.onComplete.schedule(_closeServer);
         return null;
       });
     });
   }, 'starting a server serving:\n${baseDir.describe()}');
 }
 
 /// Closes [_server]. Returns a [Future] that will complete after the [_server]
 /// is closed.
 Future _closeServer() {
-  if (_server == null) return new Future.immediate(null);
+  if (_server == null) return new Future.value();
   _server.close();
   _server = null;
   _portCompleterCache = null;
   // TODO(nweiz): Remove this once issue 4155 is fixed. Pumping the event loop
   // *seems* to be enough to ensure that the server is actually closed, but I'm
   // putting this at 10ms to be safe.
   return sleep(10);
 }
 
 /// The [d.DirectoryDescriptor] describing the server layout of packages that
@@ skipping 216 matching lines @@
     dartBin = new File(dartBin).fullPathSync();
   }
 
   // Find the main pub entrypoint.
   var pubPath = path.join(testDirectory, '..', '..', 'pub', 'pub.dart');
 
   var dartArgs = ['--package-root=$_packageRoot/', '--checked', pubPath,
       '--trace'];
   dartArgs.addAll(args);
 
-  if (tokenEndpoint == null) tokenEndpoint = new Future.immediate(null);
+  if (tokenEndpoint == null) tokenEndpoint = new Future.value();
   var optionsFuture = tokenEndpoint.then((tokenEndpoint) {
     var options = new ProcessOptions();
     options.workingDirectory = pathInSandbox(appPath);
     // TODO(nweiz): remove this when issue 9294 is fixed.
     options.environment = new Map.from(Platform.environment);
     options.environment['PUB_CACHE'] = pathInSandbox(cachePath);
     options.environment['DART_SDK'] = pathInSandbox(sdkPath);
     if (tokenEndpoint != null) {
       options.environment['_PUB_TEST_TOKEN_ENDPOINT'] =
         tokenEndpoint.toString();
@@ skipping 211 matching lines @@
 /// A function that creates a [Validator] subclass.
 typedef Validator ValidatorCreator(Entrypoint entrypoint);
 
 /// Schedules a single [Validator] to run on the [appPath]. Returns a scheduled
 /// Future that contains the errors and warnings produced by that validator.
 Future<Pair<List<String>, List<String>>> schedulePackageValidation(
     ValidatorCreator fn) {
   return schedule(() {
     var cache = new SystemCache.withSources(path.join(sandboxDir, cachePath));
 
-    return new Future.of(() {
+    return new Future.sync(() {
       var validator = fn(new Entrypoint(path.join(sandboxDir, appPath), cache));
       return validator.validate().then((_) {
         return new Pair(validator.errors, validator.warnings);
       });
     });
   }, "validating package");
 }
 
 /// A matcher that matches a Pair.
 Matcher pairOf(Matcher firstMatcher, Matcher lastMatcher) =>
    new _PairMatcher(firstMatcher, lastMatcher);
 
 class _PairMatcher extends BaseMatcher {
   final Matcher _firstMatcher;
   final Matcher _lastMatcher;
 
   _PairMatcher(this._firstMatcher, this._lastMatcher);
 
   bool matches(item, MatchState matchState) {
     if (item is! Pair) return false;
     return _firstMatcher.matches(item.first, matchState) &&
         _lastMatcher.matches(item.last, matchState);
   }
 
   Description describe(Description description) {
     description.addAll("(", ", ", ")", [_firstMatcher, _lastMatcher]);
   }
 }