Revert "Revert "Use native async/await support in pub.""

sdk/lib/_internal/pub_generated/lib/src/barback/asset_environment.dart

Index: sdk/lib/_internal/pub_generated/lib/src/barback/asset_environment.dart
diff --git a/sdk/lib/_internal/pub_generated/lib/src/barback/asset_environment.dart b/sdk/lib/_internal/pub_generated/lib/src/barback/asset_environment.dart
deleted file mode 100644
index 8316d4e4e03c93f3c52c574755708e3c5216ae8d..0000000000000000000000000000000000000000
--- a/sdk/lib/_internal/pub_generated/lib/src/barback/asset_environment.dart
+++ /dev/null
@@ -1,960 +0,0 @@
-// Copyright (c) 2014, 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 pub.barback.asset_environment;
-
-import 'dart:async';
-import 'dart:io';
-
-import 'package:barback/barback.dart';
-import 'package:path/path.dart' as path;
-import 'package:watcher/watcher.dart';
-
-import '../cached_package.dart';
-import '../entrypoint.dart';
-import '../exceptions.dart';
-import '../io.dart';
-import '../log.dart' as log;
-import '../package.dart';
-import '../package_graph.dart';
-import '../sdk.dart' as sdk;
-import '../source/cached.dart';
-import '../utils.dart';
-import 'admin_server.dart';
-import 'barback_server.dart';
-import 'dart_forwarding_transformer.dart';
-import 'dart2js_transformer.dart';
-import 'load_all_transformers.dart';
-import 'pub_package_provider.dart';
-import 'source_directory.dart';
-
-/// The entire "visible" state of the assets of a package and all of its
-/// dependencies, taking into account the user's configuration when running pub.
-///
-/// Where [PackageGraph] just describes the entrypoint's dependencies as
-/// specified by pubspecs, this includes "transient" information like the mode
-/// that the user is running pub in, or which directories they want to
-/// transform.
-class AssetEnvironment {
-  /// Creates a new build environment for working with the assets used by
-  /// [entrypoint] and its dependencies.
-  ///
-  /// HTTP servers that serve directories from this environment will be bound
-  /// to [hostname] and have ports based on [basePort]. If omitted, they
-  /// default to "localhost" and "0" (use ephemeral ports), respectively.
-  ///
-  /// Loads all used transformers using [mode] (including dart2js if
-  /// [useDart2JS] is true).
-  ///
-  /// This will only add the root package's "lib" directory to the environment.
-  /// Other directories can be added to the environment using [serveDirectory].
-  ///
-  /// If [watcherType] is not [WatcherType.NONE] (the default), watches source
-  /// assets for modification.
-  ///
-  /// If [packages] is passed, only those packages' assets are loaded and
-  /// served.
-  ///
-  /// If [entrypoints] is passed, only transformers necessary to run those
-  /// entrypoints are loaded. Each entrypoint is expected to refer to a Dart
-  /// library.
-  ///
-  /// Returns a [Future] that completes to the environment once the inputs,
-  /// transformers, and server are loaded and ready.
-  static Future<AssetEnvironment> create(Entrypoint entrypoint,
-      BarbackMode mode, {WatcherType watcherType, String hostname, int basePort,
-      Iterable<String> packages, Iterable<AssetId> entrypoints, bool useDart2JS:
-      true}) {
-    if (watcherType == null) watcherType = WatcherType.NONE;
-    if (hostname == null) hostname = "localhost";
-    if (basePort == null) basePort = 0;
-
-    return log.progress("Loading asset environment", () {
-      final completer0 = new Completer();
-      scheduleMicrotask(() {
-        try {
-          new Future.value(entrypoint.loadPackageGraph()).then((x0) {
-            try {
-              var graph = x0;
-              graph = _adjustPackageGraph(graph, mode, packages);
-              var barback = new Barback(new PubPackageProvider(graph));
-              barback.log.listen(_log);
-              var environment =
-                  new AssetEnvironment._(graph, barback, mode, watcherType, hostname, basePort);
-              new Future.value(
-                  environment._load(entrypoints: entrypoints, useDart2JS: useDart2JS)).then((x1) {
-                try {
-                  x1;
-                  completer0.complete(environment);
-                } catch (e0, s0) {
-                  completer0.completeError(e0, s0);
-                }
-              }, onError: completer0.completeError);
-            } catch (e1, s1) {
-              completer0.completeError(e1, s1);
-            }
-          }, onError: completer0.completeError);
-        } catch (e, s) {
-          completer0.completeError(e, s);
-        }
-      });
-      return completer0.future;
-    }, fine: true);
-  }
-
-  /// Return a version of [graph] that's restricted to [packages] (if passed)
-  /// and loads cached packages (if [mode] is [BarbackMode.DEBUG]).
-  static PackageGraph _adjustPackageGraph(PackageGraph graph, BarbackMode mode,
-      Iterable<String> packages) {
-    if (mode != BarbackMode.DEBUG && packages == null) return graph;
-    packages = (packages == null ? graph.packages.keys : packages).toSet();
-
-    return new PackageGraph(
-        graph.entrypoint,
-        graph.lockFile,
-        new Map.fromIterable(packages, value: (packageName) {
-      var package = graph.packages[packageName];
-      if (mode != BarbackMode.DEBUG) return package;
-      var cache = path.join('.pub/deps/debug', packageName);
-      if (!dirExists(cache)) return package;
-      return new CachedPackage(package, cache);
-    }));
-  }
-
-  /// The server for the Web Socket API and admin interface.
-  AdminServer _adminServer;
-
-  /// The public directories in the root package that are included in the asset
-  /// environment, keyed by their root directory.
-  final _directories = new Map<String, SourceDirectory>();
-
-  /// The [Barback] instance used to process assets in this environment.
-  final Barback barback;
-
-  /// The root package being built.
-  Package get rootPackage => graph.entrypoint.root;
-
-  /// The graph of packages whose assets and transformers are loaded in this
-  /// environment.
-  ///
-  /// This isn't necessarily identical to the graph that's passed in to the
-  /// environment. It may expose fewer packages if some packages' assets don't
-  /// need to be loaded, and it may expose some [CachedPackage]s.
-  final PackageGraph graph;
-
-  /// The mode to run the transformers in.
-  final BarbackMode mode;
-
-  /// The [Transformer]s that should be appended by default to the root
-  /// package's transformer cascade. Will be empty if there are none.
-  final _builtInTransformers = <Transformer>[];
-
-  /// How source files should be watched.
-  final WatcherType _watcherType;
-
-  /// The hostname that servers are bound to.
-  final String _hostname;
-
-  /// The starting number for ports that servers will be bound to.
-  ///
-  /// Servers will be bound to ports starting at this number and then
-  /// incrementing from there. However, if this is zero, then ephemeral port
-  /// numbers will be selected for each server.
-  final int _basePort;
-
-  /// The modified source assets that have not been sent to barback yet.
-  ///
-  /// The build environment can be paused (by calling [pauseUpdates]) and
-  /// resumed ([resumeUpdates]). While paused, all source asset updates that
-  /// come from watching or adding new directories are not sent to barback.
-  /// When resumed, all pending source updates are sent to barback.
-  ///
-  /// This lets pub serve and pub build create an environment and bind several
-  /// servers before barback starts building and producing results
-  /// asynchronously.
-  ///
-  /// If this is `null`, then the environment is "live" and all updates will
-  /// go to barback immediately.
-  Set<AssetId> _modifiedSources;
-
-  AssetEnvironment._(this.graph, this.barback, this.mode, this._watcherType,
-      this._hostname, this._basePort);
-
-  /// Gets the built-in [Transformer]s that should be added to [package].
-  ///
-  /// Returns `null` if there are none.
-  Iterable<Transformer> getBuiltInTransformers(Package package) {
-    // Built-in transformers only apply to the root package.
-    if (package.name != rootPackage.name) return null;
-
-    // The built-in transformers are for dart2js and forwarding assets around
-    // dart2js.
-    if (_builtInTransformers.isEmpty) return null;
-
-    return _builtInTransformers;
-  }
-
-  /// Starts up the admin server on an appropriate port and returns it.
-  ///
-  /// This may only be called once on the build environment.
-  Future<AdminServer> startAdminServer([int port]) {
-    // Can only start once.
-    assert(_adminServer == null);
-
-    // The admin server is bound to one before the base port by default, unless
-    // it's ephemeral in which case the admin port is too.
-    if (port == null) port = _basePort == 0 ? 0 : _basePort - 1;
-
-    return AdminServer.bind(this, _hostname, port).then((server) => _adminServer =
-        server);
-  }
-
-  /// Binds a new port to serve assets from within [rootDirectory] in the
-  /// entrypoint package.
-  ///
-  /// Adds and watches the sources within that directory. Returns a [Future]
-  /// that completes to the bound server.
-  ///
-  /// If [rootDirectory] is already being served, returns that existing server.
-  Future<BarbackServer> serveDirectory(String rootDirectory) {
-    // See if there is already a server bound to the directory.
-    var directory = _directories[rootDirectory];
-    if (directory != null) {
-      return directory.server.then((server) {
-        log.fine('Already serving $rootDirectory on ${server.url}.');
-        return server;
-      });
-    }
-
-    // See if the new directory overlaps any existing servers.
-    var overlapping = _directories.keys.where(
-        (directory) =>
-            path.isWithin(directory, rootDirectory) ||
-                path.isWithin(rootDirectory, directory)).toList();
-
-    if (overlapping.isNotEmpty) {
-      return new Future.error(
-          new OverlappingSourceDirectoryException(overlapping));
-    }
-
-    var port = _basePort;
-
-    // If not using an ephemeral port, find the lowest-numbered available one.
-    if (port != 0) {
-      var boundPorts =
-          _directories.values.map((directory) => directory.port).toSet();
-      while (boundPorts.contains(port)) {
-        port++;
-      }
-    }
-
-    var sourceDirectory =
-        new SourceDirectory(this, rootDirectory, _hostname, port);
-    _directories[rootDirectory] = sourceDirectory;
-
-    return _provideDirectorySources(
-        rootPackage,
-        rootDirectory).then((subscription) {
-      sourceDirectory.watchSubscription = subscription;
-      return sourceDirectory.serve();
-    });
-  }
-
-  /// Binds a new port to serve assets from within the "bin" directory of
-  /// [package].
-  ///
-  /// Adds the sources within that directory and then binds a server to it.
-  /// Unlike [serveDirectory], this works with packages that are not the
-  /// entrypoint.
-  ///
-  /// Returns a [Future] that completes to the bound server.
-  Future<BarbackServer> servePackageBinDirectory(String package) {
-    return _provideDirectorySources(
-        graph.packages[package],
-        "bin").then(
-            (_) =>
-                BarbackServer.bind(this, _hostname, 0, package: package, rootDirectory: "bin"));
-  }
-
-  /// Precompiles all of [packageName]'s executables to snapshots in
-  /// [directory].
-  ///
-  /// If [executableIds] is passed, only those executables are precompiled.
-  ///
-  /// Returns a map from executable name to path for the snapshots that were
-  /// successfully precompiled.
-  Future<Map<String, String>> precompileExecutables(String packageName,
-      String directory, {Iterable<AssetId> executableIds}) {
-    final completer0 = new Completer();
-    scheduleMicrotask(() {
-      try {
-        join0() {
-          log.fine("Executables for ${packageName}: ${executableIds}");
-          join1() {
-            var package = graph.packages[packageName];
-            new Future.value(servePackageBinDirectory(packageName)).then((x0) {
-              try {
-                var server = x0;
-                join2() {
-                  completer0.complete();
-                }
-                finally0(cont0) {
-                  server.close();
-                  cont0();
-                }
-                catch0(e1, s1) {
-                  finally0(() => completer0.completeError(e1, s1));
-                }
-                try {
-                  var precompiled = {};
-                  new Future.value(waitAndPrintErrors(executableIds.map(((id) {
-                    final completer0 = new Completer();
-                    scheduleMicrotask(() {
-                      try {
-                        var basename = path.url.basename(id.path);
-                        var snapshotPath =
-                            path.join(directory, "${basename}.snapshot");
-                        new Future.value(
-                            runProcess(
-                                Platform.executable,
-                                [
-                                    '--snapshot=${snapshotPath}',
-                                    server.url.resolve(basename).toString()])).then((x0) {
-                          try {
-                            var result = x0;
-                            join0() {
-                              completer0.complete();
-                            }
-                            if (result.success) {
-                              log.message(
-                                  "Precompiled ${_formatExecutable(id)}.");
-                              precompiled[path.withoutExtension(basename)] =
-                                  snapshotPath;
-                              join0();
-                            } else {
-                              throw new ApplicationException(
-                                  log.yellow("Failed to precompile ${_formatExecutable(id)}:\n") +
-                                      result.stderr.join('\n'));
-                              join0();
-                            }
-                          } catch (e0, s0) {
-                            completer0.completeError(e0, s0);
-                          }
-                        }, onError: completer0.completeError);
-                      } catch (e, s) {
-                        completer0.completeError(e, s);
-                      }
-                    });
-                    return completer0.future;
-                  })))).then((x1) {
-                    try {
-                      x1;
-                      final v0 = precompiled;
-                      finally0(() {
-                        completer0.complete(v0);
-                      });
-                    } catch (e2, s2) {
-                      catch0(e2, s2);
-                    }
-                  }, onError: catch0);
-                } catch (e3, s3) {
-                  catch0(e3, s3);
-                }
-              } catch (e4, s4) {
-                completer0.completeError(e4, s4);
-              }
-            }, onError: completer0.completeError);
-          }
-          if (executableIds.isEmpty) {
-            completer0.complete([]);
-          } else {
-            join1();
-          }
-        }
-        if (executableIds == null) {
-          executableIds = graph.packages[packageName].executableIds;
-          join0();
-        } else {
-          join0();
-        }
-      } catch (e, s) {
-        completer0.completeError(e, s);
-      }
-    });
-    return completer0.future;
-  }
-
-  /// Returns the executable name for [id].
-  ///
-  /// [id] is assumed to be an executable in a bin directory. The return value
-  /// is intended for log output and may contain formatting.
-  String _formatExecutable(AssetId id) =>
-      log.bold("${id.package}:${path.basenameWithoutExtension(id.path)}");
-
-  /// Stops the server bound to [rootDirectory].
-  ///
-  /// Also removes any source files within that directory from barback. Returns
-  /// the URL of the unbound server, of `null` if [rootDirectory] was not
-  /// bound to a server.
-  Future<Uri> unserveDirectory(String rootDirectory) {
-    log.fine("Unserving $rootDirectory.");
-    var directory = _directories.remove(rootDirectory);
-    if (directory == null) return new Future.value();
-
-    return directory.server.then((server) {
-      var url = server.url;
-      return directory.close().then((_) {
-        _removeDirectorySources(rootDirectory);
-        return url;
-      });
-    });
-  }
-
-  /// Gets the source directory that contains [assetPath] within the entrypoint
-  /// package.
-  ///
-  /// If [assetPath] is not contained within a source directory, this throws
-  /// an exception.
-  String getSourceDirectoryContaining(String assetPath) =>
-      _directories.values.firstWhere(
-          (dir) => path.isWithin(dir.directory, assetPath)).directory;
-
-  /// Return all URLs serving [assetPath] in this environment.
-  Future<List<Uri>> getUrlsForAssetPath(String assetPath) {
-    // Check the three (mutually-exclusive) places the path could be pointing.
-    return _lookUpPathInServerRoot(assetPath).then((urls) {
-      if (urls.isNotEmpty) return urls;
-      return _lookUpPathInPackagesDirectory(assetPath);
-    }).then((urls) {
-      if (urls.isNotEmpty) return urls;
-      return _lookUpPathInDependency(assetPath);
-    });
-  }
-
-  /// Look up [assetPath] in the root directories of servers running in the
-  /// entrypoint package.
-  Future<List<Uri>> _lookUpPathInServerRoot(String assetPath) {
-    // Find all of the servers whose root directories contain the asset and
-    // generate appropriate URLs for each.
-    return Future.wait(
-        _directories.values.where(
-            (dir) => path.isWithin(dir.directory, assetPath)).map((dir) {
-      var relativePath = path.relative(assetPath, from: dir.directory);
-      return dir.server.then(
-          (server) => server.url.resolveUri(path.toUri(relativePath)));
-    }));
-  }
-
-  /// Look up [assetPath] in the "packages" directory in the entrypoint package.
-  Future<List<Uri>> _lookUpPathInPackagesDirectory(String assetPath) {
-    var components = path.split(path.relative(assetPath));
-    if (components.first != "packages") return new Future.value([]);
-    if (!graph.packages.containsKey(components[1])) return new Future.value([]);
-    return Future.wait(_directories.values.map((dir) {
-      return dir.server.then(
-          (server) => server.url.resolveUri(path.toUri(assetPath)));
-    }));
-  }
-
-  /// Look up [assetPath] in the "lib" or "asset" directory of a dependency
-  /// package.
-  Future<List<Uri>> _lookUpPathInDependency(String assetPath) {
-    for (var packageName in graph.packages.keys) {
-      var package = graph.packages[packageName];
-      var libDir = package.path('lib');
-      var assetDir = package.path('asset');
-
-      var uri;
-      if (path.isWithin(libDir, assetPath)) {
-        uri = path.toUri(
-            path.join('packages', package.name, path.relative(assetPath, from: libDir)));
-      } else if (path.isWithin(assetDir, assetPath)) {
-        uri = path.toUri(
-            path.join('assets', package.name, path.relative(assetPath, from: assetDir)));
-      } else {
-        continue;
-      }
-
-      return Future.wait(_directories.values.map((dir) {
-        return dir.server.then((server) => server.url.resolveUri(uri));
-      }));
-    }
-
-    return new Future.value([]);
-  }
-
-  /// Given a URL to an asset served by this environment, returns the ID of the
-  /// asset that would be accessed by that URL.
-  ///
-  /// If no server can serve [url], completes to `null`.
-  Future<AssetId> getAssetIdForUrl(Uri url) {
-    return Future.wait(
-        _directories.values.map((dir) => dir.server)).then((servers) {
-      var server = servers.firstWhere((server) {
-        if (server.port != url.port) return false;
-        return isLoopback(server.address.host) == isLoopback(url.host) ||
-            server.address.host == url.host;
-      }, orElse: () => null);
-      if (server == null) return null;
-      return server.urlToId(url);
-    });
-  }
-
-  /// Determines if [sourcePath] is contained within any of the directories in
-  /// the root package that are visible to this build environment.
-  bool containsPath(String sourcePath) {
-    var directories = ["lib"];
-    directories.addAll(_directories.keys);
-    return directories.any((dir) => path.isWithin(dir, sourcePath));
-  }
-
-  /// Pauses sending source asset updates to barback.
-  void pauseUpdates() {
-    // Cannot pause while already paused.
-    assert(_modifiedSources == null);
-
-    _modifiedSources = new Set<AssetId>();
-  }
-
-  /// Sends any pending source updates to barback and begins the asynchronous
-  /// build process.
-  void resumeUpdates() {
-    // Cannot resume while not paused.
-    assert(_modifiedSources != null);
-
-    barback.updateSources(_modifiedSources);
-    _modifiedSources = null;
-  }
-
-  /// Loads the assets and transformers for this environment.
-  ///
-  /// This transforms and serves all library and asset files in all packages in
-  /// the environment's package graph. It loads any transformer plugins defined
-  /// in packages in [graph] and re-runs them as necessary when any input files
-  /// change.
-  ///
-  /// If [useDart2JS] is `true`, then the [Dart2JSTransformer] is implicitly
-  /// added to end of the root package's transformer phases.
-  ///
-  /// If [entrypoints] is passed, only transformers necessary to run those
-  /// entrypoints will be loaded.
-  ///
-  /// Returns a [Future] that completes once all inputs and transformers are
-  /// loaded.
-  Future _load({Iterable<AssetId> entrypoints, bool useDart2JS}) {
-    return log.progress("Initializing barback", () {
-      final completer0 = new Completer();
-      scheduleMicrotask(() {
-        try {
-          var containsDart2JS =
-              graph.entrypoint.root.pubspec.transformers.any(((transformers) {
-            return transformers.any(
-                (config) => config.id.package == '\$dart2js');
-          }));
-          join0() {
-            new Future.value(BarbackServer.bind(this, _hostname, 0)).then((x0) {
-              try {
-                var transformerServer = x0;
-                var errorStream = barback.errors.map(((error) {
-                  if (error is! AssetLoadException) throw error;
-                  log.error(log.red(error.message));
-                  log.fine(error.stackTrace.terse);
-                }));
-                new Future.value(_withStreamErrors((() {
-                  return log.progress("Loading source assets", _provideSources);
-                }), [errorStream, barback.results])).then((x1) {
-                  try {
-                    x1;
-                    log.fine("Provided sources.");
-                    errorStream = barback.errors.map(((error) {
-                      if (error is! TransformerException) throw error;
-                      var message = error.error.toString();
-                      if (error.stackTrace != null) {
-                        message += "\n" + error.stackTrace.terse.toString();
-                      }
-                      _log(
-                          new LogEntry(
-                              error.transform,
-                              error.transform.primaryId,
-                              LogLevel.ERROR,
-                              message,
-                              null));
-                    }));
-                    new Future.value(_withStreamErrors((() {
-                      final completer0 = new Completer();
-                      scheduleMicrotask(() {
-                        try {
-                          completer0.complete(
-                              log.progress("Loading transformers", (() {
-                            final completer0 = new Completer();
-                            scheduleMicrotask(() {
-                              try {
-                                new Future.value(
-                                    loadAllTransformers(
-                                        this,
-                                        transformerServer,
-                                        entrypoints: entrypoints)).then((x0) {
-                                  try {
-                                    x0;
-                                    transformerServer.close();
-                                    completer0.complete();
-                                  } catch (e0, s0) {
-                                    completer0.completeError(e0, s0);
-                                  }
-                                }, onError: completer0.completeError);
-                              } catch (e, s) {
-                                completer0.completeError(e, s);
-                              }
-                            });
-                            return completer0.future;
-                          }), fine: true));
-                        } catch (e, s) {
-                          completer0.completeError(e, s);
-                        }
-                      });
-                      return completer0.future;
-                    }),
-                        [errorStream, barback.results, transformerServer.results])).then((x2) {
-                      try {
-                        x2;
-                        completer0.complete();
-                      } catch (e0, s0) {
-                        completer0.completeError(e0, s0);
-                      }
-                    }, onError: completer0.completeError);
-                  } catch (e1, s1) {
-                    completer0.completeError(e1, s1);
-                  }
-                }, onError: completer0.completeError);
-              } catch (e2, s2) {
-                completer0.completeError(e2, s2);
-              }
-            }, onError: completer0.completeError);
-          }
-          if (!containsDart2JS && useDart2JS) {
-            _builtInTransformers.addAll(
-                [new Dart2JSTransformer(this, mode), new DartForwardingTransformer(mode)]);
-            join0();
-          } else {
-            join0();
-          }
-        } catch (e, s) {
-          completer0.completeError(e, s);
-        }
-      });
-      return completer0.future;
-    }, fine: true);
-  }
-
-  /// Provides the public source assets in the environment to barback.
-  ///
-  /// If [watcherType] is not [WatcherType.NONE], enables watching on them.
-  Future _provideSources() {
-    final completer0 = new Completer();
-    scheduleMicrotask(() {
-      try {
-        new Future.value(Future.wait(graph.packages.values.map(((package) {
-          final completer0 = new Completer();
-          scheduleMicrotask(() {
-            try {
-              join0() {
-                new Future.value(
-                    _provideDirectorySources(package, "lib")).then((x0) {
-                  try {
-                    x0;
-                    completer0.complete();
-                  } catch (e0, s0) {
-                    completer0.completeError(e0, s0);
-                  }
-                }, onError: completer0.completeError);
-              }
-              if (graph.isPackageStatic(package.name)) {
-                completer0.complete(null);
-              } else {
-                join0();
-              }
-            } catch (e, s) {
-              completer0.completeError(e, s);
-            }
-          });
-          return completer0.future;
-        })))).then((x0) {
-          try {
-            x0;
-            completer0.complete();
-          } catch (e0, s0) {
-            completer0.completeError(e0, s0);
-          }
-        }, onError: completer0.completeError);
-      } catch (e, s) {
-        completer0.completeError(e, s);
-      }
-    });
-    return completer0.future;
-  }
-
-  /// Provides all of the source assets within [dir] in [package] to barback.
-  ///
-  /// If [watcherType] is not [WatcherType.NONE], enables watching on them.
-  /// Returns the subscription to the watcher, or `null` if none was created.
-  Future<StreamSubscription<WatchEvent>>
-      _provideDirectorySources(Package package, String dir) {
-    log.fine("Providing sources for ${package.name}|$dir.");
-    // TODO(rnystrom): Handle overlapping directories. If two served
-    // directories overlap like so:
-    //
-    // $ pub serve example example/subdir
-    //
-    // Then the sources of the subdirectory will be updated and watched twice.
-    // See: #17454
-    if (_watcherType == WatcherType.NONE) {
-      _updateDirectorySources(package, dir);
-      return new Future.value();
-    }
-
-    // Watch the directory before listing is so we don't miss files that
-    // are added between the initial list and registering the watcher.
-    return _watchDirectorySources(package, dir).then((_) {
-      _updateDirectorySources(package, dir);
-    });
-  }
-
-  /// Updates barback with all of the files in [dir] inside [package].
-  void _updateDirectorySources(Package package, String dir) {
-    var ids = _listDirectorySources(package, dir);
-    if (_modifiedSources == null) {
-      barback.updateSources(ids);
-    } else {
-      _modifiedSources.addAll(ids);
-    }
-  }
-
-  /// Removes all of the files in [dir] in the root package from barback.
-  void _removeDirectorySources(String dir) {
-    var ids = _listDirectorySources(rootPackage, dir);
-    if (_modifiedSources == null) {
-      barback.removeSources(ids);
-    } else {
-      _modifiedSources.removeAll(ids);
-    }
-  }
-
-  /// Lists all of the source assets in [dir] inside [package].
-  ///
-  /// For large packages, listing the contents is a performance bottleneck, so
-  /// this is optimized for our needs in here instead of using the more general
-  /// but slower [listDir].
-  Iterable<AssetId> _listDirectorySources(Package package, String dir) {
-    // This is used in some performance-sensitive paths and can list many, many
-    // files. As such, it leans more havily towards optimization as opposed to
-    // readability than most code in pub. In particular, it avoids using the
-    // path package, since re-parsing a path is very expensive relative to
-    // string operations.
-    return package.listFiles(beneath: dir).map((file) {
-      // From profiling, path.relative here is just as fast as a raw substring
-      // and is correct in the case where package.dir has a trailing slash.
-      var relative = package.relative(file);
-
-      if (Platform.operatingSystem == 'windows') {
-        relative = relative.replaceAll("\\", "/");
-      }
-
-      var uri = new Uri(pathSegments: relative.split("/"));
-      return new AssetId(package.name, uri.toString());
-    });
-  }
-
-  /// Adds a file watcher for [dir] within [package], if the directory exists
-  /// and the package needs watching.
-  Future<StreamSubscription<WatchEvent>> _watchDirectorySources(Package package,
-      String dir) {
-    // If this package comes from a cached source, its contents won't change so
-    // we don't need to monitor it. `packageId` will be null for the
-    // application package, since that's not locked.
-    var packageId = graph.lockFile.packages[package.name];
-    if (packageId != null &&
-        graph.entrypoint.cache.sources[packageId.source] is CachedSource) {
-      return new Future.value();
-    }
-
-    var subdirectory = package.path(dir);
-    if (!dirExists(subdirectory)) return new Future.value();
-
-    // TODO(nweiz): close this watcher when [barback] is closed.
-    var watcher = _watcherType.create(subdirectory);
-    var subscription = watcher.events.listen((event) {
-      // Don't watch files symlinked into these directories.
-      // TODO(rnystrom): If pub gets rid of symlinks, remove this.
-      var parts = path.split(event.path);
-      if (parts.contains("packages")) return;
-
-      // Skip files that were (most likely) compiled from nearby ".dart"
-      // files. These are created by the Editor's "Run as JavaScript"
-      // command and are written directly into the package's directory.
-      // When pub's dart2js transformer then tries to create the same file
-      // name, we get a build error. To avoid that, just don't consider
-      // that file to be a source.
-      // TODO(rnystrom): Remove these when the Editor no longer generates
-      // .js files and users have had enough time that they no longer have
-      // these files laying around. See #15859.
-      if (event.path.endsWith(".dart.js")) return;
-      if (event.path.endsWith(".dart.js.map")) return;
-      if (event.path.endsWith(".dart.precompiled.js")) return;
-
-      var idPath = package.relative(event.path);
-      var id = new AssetId(package.name, path.toUri(idPath).toString());
-      if (event.type == ChangeType.REMOVE) {
-        if (_modifiedSources != null) {
-          _modifiedSources.remove(id);
-        } else {
-          barback.removeSources([id]);
-        }
-      } else if (_modifiedSources != null) {
-        _modifiedSources.add(id);
-      } else {
-        barback.updateSources([id]);
-      }
-    });
-
-    return watcher.ready.then((_) => subscription);
-  }
-
-  /// Returns the result of [futureCallback] unless any stream in [streams]
-  /// emits an error before it's done.
-  ///
-  /// If a stream does emit an error, that error is thrown instead.
-  /// [futureCallback] is a callback rather than a plain future to ensure that
-  /// [streams] are listened to before any code that might cause an error starts
-  /// running.
-  Future _withStreamErrors(Future futureCallback(), List<Stream> streams) {
-    var completer = new Completer.sync();
-    var subscriptions = streams.map(
-        (stream) => stream.listen((_) {}, onError: completer.completeError)).toList();
-
-    new Future.sync(futureCallback).then((_) {
-      if (!completer.isCompleted) completer.complete();
-    }).catchError((error, stackTrace) {
-      if (!completer.isCompleted) completer.completeError(error, stackTrace);
-    });
-
-    return completer.future.whenComplete(() {
-      for (var subscription in subscriptions) {
-        subscription.cancel();
-      }
-    });
-  }
-}
-
-/// Log [entry] using Pub's logging infrastructure.
-///
-/// Since both [LogEntry] objects and the message itself often redundantly
-/// show the same context like the file where an error occurred, this tries
-/// to avoid showing redundant data in the entry.
-void _log(LogEntry entry) {
-  messageMentions(text) =>
-      entry.message.toLowerCase().contains(text.toLowerCase());
-
-  messageMentionsAsset(id) =>
-      messageMentions(id.toString()) ||
-          messageMentions(path.fromUri(entry.assetId.path));
-
-  var prefixParts = [];
-
-  // Show the level (unless the message mentions it).
-  if (!messageMentions(entry.level.name)) {
-    prefixParts.add("${entry.level} from");
-  }
-
-  // Show the transformer.
-  prefixParts.add(entry.transform.transformer);
-
-  // Mention the primary input of the transform unless the message seems to.
-  if (!messageMentionsAsset(entry.transform.primaryId)) {
-    prefixParts.add("on ${entry.transform.primaryId}");
-  }
-
-  // If the relevant asset isn't the primary input, mention it unless the
-  // message already does.
-  if (entry.assetId != entry.transform.primaryId &&
-      !messageMentionsAsset(entry.assetId)) {
-    prefixParts.add("with input ${entry.assetId}");
-  }
-
-  var prefix = "[${prefixParts.join(' ')}]:";
-  var message = entry.message;
-  if (entry.span != null) {
-    message = entry.span.message(entry.message);
-  }
-
-  switch (entry.level) {
-    case LogLevel.ERROR:
-      log.error("${log.red(prefix)}\n$message");
-      break;
-
-    case LogLevel.WARNING:
-      log.warning("${log.yellow(prefix)}\n$message");
-      break;
-
-    case LogLevel.INFO:
-      log.message("${log.cyan(prefix)}\n$message");
-      break;
-
-    case LogLevel.FINE:
-      log.fine("${log.gray(prefix)}\n$message");
-      break;
-  }
-}
-
-/// Exception thrown when trying to serve a new directory that overlaps one or
-/// more directories already being served.
-class OverlappingSourceDirectoryException implements Exception {
-  /// The relative paths of the directories that overlap the one that could not
-  /// be served.
-  final List<String> overlappingDirectories;
-
-  OverlappingSourceDirectoryException(this.overlappingDirectories);
-}
-
-/// An enum describing different modes of constructing a [DirectoryWatcher].
-abstract class WatcherType {
-  /// A watcher that automatically chooses its type based on the operating
-  /// system.
-  static const AUTO = const _AutoWatcherType();
-
-  /// A watcher that always polls the filesystem for changes.
-  static const POLLING = const _PollingWatcherType();
-
-  /// No directory watcher at all.
-  static const NONE = const _NoneWatcherType();
-
-  /// Creates a new DirectoryWatcher.
-  DirectoryWatcher create(String directory);
-
-  String toString();
-}
-
-class _AutoWatcherType implements WatcherType {
-  const _AutoWatcherType();
-
-  DirectoryWatcher create(String directory) => new DirectoryWatcher(directory);
-
-  String toString() => "auto";
-}
-
-class _PollingWatcherType implements WatcherType {
-  const _PollingWatcherType();
-
-  DirectoryWatcher create(String directory) =>
-      new PollingDirectoryWatcher(directory);
-
-  String toString() => "polling";
-}
-
-class _NoneWatcherType implements WatcherType {
-  const _NoneWatcherType();
-
-  DirectoryWatcher create(String directory) => null;
-
-  String toString() => "none";
-}