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barback/lib/src/utils.dart

Index: barback/lib/src/utils.dart
diff --git a/barback/lib/src/utils.dart b/barback/lib/src/utils.dart
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-// 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.
-
-library barback.utils;
-
-import 'dart:async';
-import 'dart:typed_data';
-
-import 'package:stack_trace/stack_trace.dart';
-
-/// A class that represents a value or an error.
-class Fallible<E> {
-  /// Whether [this] has a [value], as opposed to an [error].
-  final bool hasValue;
-
-  /// Whether [this] has an [error], as opposed to a [value].
-  bool get hasError => !hasValue;
-
-  /// The value.
-  ///
-  /// This will be `null` if [this] has an [error].
-  final E _value;
-
-  /// The value.
-  ///
-  /// This will throw a [StateError] if [this] has an [error].
-  E get value {
-    if (hasValue) return _value;
-    throw new StateError("Fallible has no value.\n"
-        "$_error$_stackTraceSuffix");
-  }
-
-  /// The error.
-  ///
-  /// This will be `null` if [this] has a [value].
-  final _error;
-
-  /// The error.
-  ///
-  /// This will throw a [StateError] if [this] has a [value].
-  get error {
-    if (hasError) return _error;
-    throw new StateError("Fallible has no error.");
-  }
-
-  /// The stack trace for [_error].
-  ///
-  /// This will be `null` if [this] has a [value], or if no stack trace was
-  /// provided.
-  final StackTrace _stackTrace;
-
-  /// The stack trace for [error].
-  ///
-  /// This will throw a [StateError] if [this] has a [value].
-  StackTrace get stackTrace {
-    if (hasError) return _stackTrace;
-    throw new StateError("Fallible has no error.");
-  }
-
-  Fallible.withValue(this._value)
-      : _error = null,
-        _stackTrace = null,
-        hasValue = true;
-
-  Fallible.withError(this._error, [this._stackTrace])
-      : _value = null,
-        hasValue = false;
-
-  /// Returns a completed Future with the same value or error as [this].
-  Future toFuture() {
-    if (hasValue) return new Future.value(value);
-    return new Future.error(error, stackTrace);
-  }
-
-  String toString() {
-    if (hasValue) return "Fallible value: $value";
-    return "Fallible error: $error$_stackTraceSuffix";
-  }
-
-  String get _stackTraceSuffix {
-    if (stackTrace == null) return "";
-    return "\nStack trace:\n${new Chain.forTrace(_stackTrace).terse}";
-  }
-}
-
-/// Converts a number in the range [0-255] to a two digit hex string.
-///
-/// For example, given `255`, returns `ff`.
-String byteToHex(int byte) {
-  assert(byte >= 0 && byte <= 255);
-
-  const DIGITS = "0123456789abcdef";
-  return DIGITS[(byte ~/ 16) % 16] + DIGITS[byte % 16];
-}
-
-/// Returns a sentence fragment listing the elements of [iter].
-///
-/// This converts each element of [iter] to a string and separates them with
-/// commas and/or "and" where appropriate.
-String toSentence(Iterable iter) {
-  if (iter.length == 1) return iter.first.toString();
-  return iter.take(iter.length - 1).join(", ") + " and ${iter.last}";
-}
-
-/// Returns [name] if [number] is 1, or the plural of [name] otherwise.
-///
-/// By default, this just adds "s" to the end of [name] to get the plural. If
-/// [plural] is passed, that's used instead.
-String pluralize(String name, int number, {String plural}) {
-  if (number == 1) return name;
-  if (plural != null) return plural;
-  return '${name}s';
-}
-
-/// Converts [input] into a [Uint8List].
-///
-/// If [input] is a [TypedData], this just returns a view on [input].
-Uint8List toUint8List(List<int> input) {
-  if (input is Uint8List) return input;
-  if (input is TypedData) {
-    // TODO(nweiz): remove "as" when issue 11080 is fixed.
-    return new Uint8List.view((input as TypedData).buffer);
-  }
-  return new Uint8List.fromList(input);
-}
-
-/// Group the elements in [iter] by the value returned by [fn].
-///
-/// This returns a map whose keys are the return values of [fn] and whose values
-/// are lists of each element in [iter] for which [fn] returned that key.
-Map<Object, List> groupBy(Iterable iter, fn(element)) {
-  var map = {};
-  for (var element in iter) {
-    var list = map.putIfAbsent(fn(element), () => []);
-    list.add(element);
-  }
-  return map;
-}
-
-/// Flattens nested lists inside an iterable into a single list containing only
-/// non-list elements.
-List flatten(Iterable nested) {
-  var result = [];
-  helper(list) {
-    for (var element in list) {
-      if (element is List) {
-        helper(element);
-      } else {
-        result.add(element);
-      }
-    }
-  }
-  helper(nested);
-  return result;
-}
-
-/// Returns the union of all elements in each set in [sets].
-Set unionAll(Iterable<Set> sets) =>
-  sets.fold(new Set(), (union, set) => union.union(set));
-
-/// Creates a new map from [map] with new keys and values.
-///
-/// The return values of [keyFn] are used as the keys and the return values of
-/// [valueFn] are used as the values for the new map.
-Map mapMap(Map map, keyFn(key, value), valueFn(key, value)) =>
-  new Map.fromIterable(map.keys,
-      key: (key) => keyFn(key, map[key]),
-      value: (key) => valueFn(key, map[key]));
-
-/// Creates a new map from [map] with the same keys.
-///
-/// The return values of [fn] are used as the values for the new map.
-Map mapMapValues(Map map, fn(key, value)) => mapMap(map, (key, _) => key, fn);
-
-/// Creates a new map from [map] with the same keys.
-///
-/// The return values of [fn] are used as the keys for the new map.
-Map mapMapKeys(Map map, fn(key, value)) => mapMap(map, fn, (_, value) => value);
-
-/// Returns whether [set1] has exactly the same elements as [set2].
-bool setEquals(Set set1, Set set2) =>
-  set1.length == set2.length && set1.containsAll(set2);
-
-/// Merges [streams] into a single stream that emits events from all sources.
-///
-/// If [broadcast] is true, this will return a broadcast stream; otherwise, it
-/// will return a buffered stream.
-Stream mergeStreams(Iterable<Stream> streams, {bool broadcast: false}) {
-  streams = streams.toList();
-  var doneCount = 0;
-  // Use a sync stream to preserve the synchrony behavior of the input streams.
-  // If the inputs are sync, then this will be sync as well; if the inputs are
-  // async, then the events we receive will also be async, and forwarding them
-  // sync won't change that.
-  var controller = broadcast ? new StreamController.broadcast(sync: true)
-      : new StreamController(sync: true);
-
-  for (var stream in streams) {
-    stream.listen(
-        controller.add,
-        onError: controller.addError,
-        onDone: () {
-      doneCount++;
-      if (doneCount == streams.length) controller.close();
-    });
-  }
-
-  return controller.stream;
-}
-
-/// Prepends each line in [text] with [prefix]. If [firstPrefix] is passed, the
-/// first line is prefixed with that instead.
-String prefixLines(String text, {String prefix: '| ', String firstPrefix}) {
-  var lines = text.split('\n');
-  if (firstPrefix == null) {
-    return lines.map((line) => '$prefix$line').join('\n');
-  }
-
-  var firstLine = "$firstPrefix${lines.first}";
-  lines = lines.skip(1).map((line) => '$prefix$line').toList();
-  lines.insert(0, firstLine);
-  return lines.join('\n');
-}
-
-/// Returns a [Future] that completes after pumping the event queue [times]
-/// times. By default, this should pump the event queue enough times to allow
-/// any code to run, as long as it's not waiting on some external event.
-Future pumpEventQueue([int times=20]) {
-  if (times == 0) return new Future.value();
-  // We use a delayed future to allow microtask events to finish. The
-  // Future.value or Future() constructors use scheduleMicrotask themselves and
-  // would therefore not wait for microtask callbacks that are scheduled after
-  // invoking this method.
-  return new Future.delayed(Duration.ZERO, () => pumpEventQueue(times - 1));
-}
-
-/// Like `new Future`, but avoids issue 11911 by using `new Future.value` under
-/// the covers.
-// TODO(jmesserly): doc comment changed to due 14601.
-Future newFuture(callback()) => new Future.value().then((_) => callback());
-
-/// Like [Future.sync], but wraps the Future in [Chain.track] as well.
-Future syncFuture(callback()) => Chain.track(new Future.sync(callback));
-
-/// Returns a buffered stream that will emit the same values as the stream
-/// returned by [future] once [future] completes.
-///
-/// If [future] completes to an error, the return value will emit that error and
-/// then close.
-///
-/// If [broadcast] is true, a broadcast stream is returned. This assumes that
-/// the stream returned by [future] will be a broadcast stream as well.
-/// [broadcast] defaults to false.
-Stream futureStream(Future<Stream> future, {bool broadcast: false}) {
-  var subscription;
-  var controller;
-
-  future = future.catchError((e, stackTrace) {
-    // Since [controller] is synchronous, it's likely that emitting an error
-    // will cause it to be cancelled before we call close.
-    if (controller != null) controller.addError(e, stackTrace);
-    if (controller != null) controller.close();
-    controller = null;
-  });
-
-  onListen() {
-    future.then((stream) {
-      if (controller == null) return;
-      subscription = stream.listen(
-          controller.add,
-          onError: controller.addError,
-          onDone: controller.close);
-    });
-  }
-
-  onCancel() {
-    if (subscription != null) subscription.cancel();
-    subscription = null;
-    controller = null;
-  }
-
-  if (broadcast) {
-    controller = new StreamController.broadcast(
-        sync: true, onListen: onListen, onCancel: onCancel);
-  } else {
-    controller = new StreamController(
-        sync: true, onListen: onListen, onCancel: onCancel);
-  }
-  return controller.stream;
-}
-
-/// Returns a [Stream] that will emit the same values as the stream returned by
-/// [callback].
-///
-/// [callback] will only be called when the returned [Stream] gets a subscriber.
-Stream callbackStream(Stream callback()) {
-  var subscription;
-  var controller;
-  controller = new StreamController(onListen: () {
-    subscription = callback().listen(controller.add,
-        onError: controller.addError,
-        onDone: controller.close);
-  },
-      onCancel: () => subscription.cancel(),
-      onPause: () => subscription.pause(),
-      onResume: () => subscription.resume(),
-      sync: true);
-  return controller.stream;
-}
-
-/// Creates a single-subscription stream from a broadcast stream.
-///
-/// The returned stream will enqueue events from [broadcast] until a listener is
-/// attached, then pipe events to that listener.
-Stream broadcastToSingleSubscription(Stream broadcast) {
-  if (!broadcast.isBroadcast) return broadcast;
-
-  // TODO(nweiz): Implement this using a transformer when issues 18588 and 18586
-  // are fixed.
-  var subscription;
-  var controller = new StreamController(onCancel: () => subscription.cancel());
-  subscription = broadcast.listen(controller.add,
-      onError: controller.addError,
-      onDone: controller.close);
-  return controller.stream;
-}
-
-/// A regular expression to match the exception prefix that some exceptions'
-/// [Object.toString] values contain.
-final _exceptionPrefix = new RegExp(r'^([A-Z][a-zA-Z]*)?(Exception|Error): ');
-
-/// Get a string description of an exception.
-///
-/// Many exceptions include the exception class name at the beginning of their
-/// [toString], so we remove that if it exists.
-String getErrorMessage(error) =>
-  error.toString().replaceFirst(_exceptionPrefix, '');
-
-/// Returns a human-friendly representation of [duration].
-String niceDuration(Duration duration) {
-  var result = duration.inMinutes > 0 ? "${duration.inMinutes}:" : "";
-
-  var s = duration.inSeconds % 59;
-  var ms = (duration.inMilliseconds % 1000) ~/ 100;
-  return result + "$s.${ms}s";
-}