Make a bunch of stuff in pub synchronous.

utils/tests/pub/test_pub.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.
 
 /// 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 567 matching lines @@
 
   pub.writeLine("y");
 }
 
 
 /// Calls [fn] with appropriately modified arguments to run a pub process. [fn]
 /// should have the same signature as [startProcess], except that the returned
 /// [Future] may have a type other than [Process].
 Future _doPub(Function fn, sandboxDir, List args, Future<Uri> tokenEndpoint) {
   String pathInSandbox(path) => join(getFullPath(sandboxDir), path);
-
-  return Future.wait([
-    ensureDir(pathInSandbox(appPath)),
-    _awaitObject(args),
-    tokenEndpoint == null ? new Future.immediate(null) : tokenEndpoint
-  ]).then((results) {
-    var args = results[1];
-    var tokenEndpoint = results[2];
+  // Make sure all errors propagate through future.
+  return defer(() {
+    ensureDir(pathInSandbox(appPath));
+    return Future.wait([
+      _awaitObject(args),
+      tokenEndpoint == null ? new Future.immediate(null) : tokenEndpoint
+    ]);
+  }).then((results) {
+    var args = results[0];
+    var tokenEndpoint = results[1];
     // Find a Dart executable we can use to spawn. Use the same one that was
     // used to run this script itself.
     var dartBin = new Options().executable;
 
     // If the executable looks like a path, get its full path. That way we
     // can still find it when we spawn it with a different working directory.
     if (dartBin.contains(Platform.pathSeparator)) {
       dartBin = new File(dartBin).fullPathSync();
     }
 
@@ skipping 187 matching lines @@
   /// directory.
   void scheduleValidate() => _schedule((parentDir) => validate(parentDir.path));
 
   /// Asserts that the name of the descriptor is a [String] and returns it.
   String get _stringName {
     if (name is String) return name;
     throw 'Pattern $name must be a string.';
   }
 
   /// Validates that at least one file in [dir] matching [name] is valid
-  /// according to [validate]. [validate] should complete to an exception if
-  /// the input path is invalid.
+  /// according to [validate]. [validate] should throw or complete to an
+  /// exception if the input path is invalid.
   Future _validateOneMatch(String dir, Future validate(String path)) {
     // Special-case strings to support multi-level names like "myapp/packages".
     if (name is String) {
       var path = join(dir, name);
-      return exists(path).then((exists) {
-        if (!exists) {
+      // Make sure errors propagate through future.
+      return defer(() {
+        if (!entryExists(path)) {
           throw new ExpectException('File $name in $dir not found.');
         }
         return validate(path);
       });
     }
 
     // TODO(nweiz): remove this when issue 4061 is fixed.
     var stackTrace;
     try {
       throw "";
@@ skipping 45 matching lines @@
 /// tree before running a test, and for validating that the file system matches
 /// some expectations after running it.
 class FileDescriptor extends Descriptor {
   /// The text contents of the file.
   final String contents;
 
   FileDescriptor(Pattern name, this.contents) : super(name);
 
   /// Creates the file within [dir]. Returns a [Future] that is completed after
   /// the creation is done.
-  Future<File> create(dir) {
-    return writeTextFile(join(dir, _stringName), contents);
-  }
+  Future<File> create(dir) =>
+      defer(() => writeTextFile(join(dir, _stringName), contents));
 
   /// Deletes the file within [dir]. Returns a [Future] that is completed after
   /// the deletion is done.
-  Future delete(dir) {
-    return deleteFile(join(dir, _stringName));
-  }
+  Future delete(dir) =>
+      defer(() => deleteFile(join(dir, _stringName)));
 
   /// Validates that this file correctly matches the actual file at [path].
   Future validate(String path) {
     return _validateOneMatch(path, (file) {
-      return readTextFile(file).then((text) {
-        if (text == contents) return null;
+      var text = readTextFile(file);
+      if (text == contents) return null;
 
-        throw new ExpectException(
-            'File $file should contain:\n\n$contents\n\n'
-            'but contained:\n\n$text');
-      });
+      throw new ExpectException(
+          'File $file should contain:\n\n$contents\n\n'
+          'but contained:\n\n$text');
     });
   }
 
   /// Loads the contents of the file.
   InputStream load(List<String> path) {
     if (!path.isEmpty) {
       var joinedPath = Strings.join(path, '/');
       throw "Can't load $joinedPath from within $name: not a directory.";
     }
 
@@ skipping 11 matching lines @@
   /// The files and directories contained in this directory.
   final List<Descriptor> contents;
 
   DirectoryDescriptor(Pattern name, List<Descriptor> contents)
     : this.contents = contents == null ? <Descriptor>[] : contents,
       super(name);
 
   /// Creates the file within [dir]. Returns a [Future] that is completed after
   /// the creation is done.
   Future<Directory> create(parentDir) {
-    // Create the directory.
-    return ensureDir(join(parentDir, _stringName)).then((dir) {
-      if (contents == null) return new Future<Directory>.immediate(dir);
+    // Make sure all errors propagate through the future.
+    return defer(() {
+      // Create the directory.
+      var dir = ensureDir(join(parentDir, _stringName));
+      if (contents == null) return dir;
 
       // Recursively create all of its children.
-      final childFutures =
-          contents.map((child) => child.create(dir)).toList();
+      var childFutures = contents.map((child) => child.create(dir)).toList();
       // Only complete once all of the children have been created too.
       return Future.wait(childFutures).then((_) => dir);
     });
   }
 
   /// Deletes the directory within [dir]. Returns a [Future] that is completed
   /// after the deletion is done.
   Future delete(dir) {
     return deleteDir(join(dir, _stringName));
   }
@@ skipping 183 matching lines @@
 }
 
 /// A descriptor that validates that no file exists with the given name.
 class NothingDescriptor extends Descriptor {
   NothingDescriptor(String name) : super(name);
 
   Future create(dir) => new Future.immediate(null);
   Future delete(dir) => new Future.immediate(null);
 
   Future validate(String dir) {
-    return exists(join(dir, name)).then((exists) {
-      if (exists) {
+    // Make sure errors propagate through future.
+    return defer(() {
+      if (entryExists(join(dir, name))) {
         throw new ExpectException('File $name in $dir should not exist.');
       }
     });
   }
 
   InputStream load(List<String> path) {
     if (path.isEmpty) {
       throw "Can't load the contents of $name: it doesn't exist.";
     } else {
       throw "Can't load ${Strings.join(path, '/')} from within $name: $name "
         "doesn't exist.";
     }
   }
 }
 
 /// 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 erros and warnings produced by that validator.
 Future<Pair<List<String>, List<String>>> schedulePackageValidation(
     ValidatorCreator fn) {
   return _scheduleValue((sandboxDir) {
-    var cache = new SystemCache.withSources(
-        join(sandboxDir, cachePath));
+    var cache = new SystemCache.withSources(join(sandboxDir, cachePath));
 
-    return Entrypoint.load(join(sandboxDir, appPath), cache)
-        .then((entrypoint) {
-      var validator = fn(entrypoint);
+    return defer(() {
+      var validator = fn(new Entrypoint(join(sandboxDir, appPath), cache));
       return validator.validate().then((_) {
         return new Pair(validator.errors, validator.warnings);
       });
     });
   });
 }
 
 /// A matcher that matches a Pair.
 Matcher pairOf(Matcher firstMatcher, Matcher lastMatcher) =>
    new _PairMatcher(firstMatcher, lastMatcher);
@@ skipping 288 matching lines @@
   }
 
   /// Ignore all requests with the given [method] and [path]. If one is
   /// received, don't respond to it.
   void ignore(String method, String path) =>
     _ignored.add(new Pair(method, path));
 
   /// Raises an error complaining of an unexpected request.
   void _awaitHandle(HttpRequest request, HttpResponse response) {
     if (_ignored.contains(new Pair(request.method, request.path))) return;
-    var future = timeout(new Future.immediate(null).then((_) {
+    // Make sure all errors propagate through future.
+    var future = timeout(defer(() {
       if (_handlers.isEmpty) {
         fail('Unexpected ${request.method} request to ${request.path}.');
       }
       return _handlers.removeFirst();
     }).then((handler) {
       handler(request, response);
     }), _SCHEDULE_TIMEOUT, "waiting for a handler for ${request.method} "
         "${request.path}");
     expect(future, completes);
   }
@@ skipping 63 matching lines @@
 /// calling [completion] is unnecessary.
 void expectLater(Future actual, matcher, {String reason,
     FailureHandler failureHandler, bool verbose: false}) {
   _schedule((_) {
     return actual.then((value) {
       expect(value, matcher, reason: reason, failureHandler: failureHandler,
           verbose: false);
     });
   });
 }