Validate packages against their SDK constraints.

utils/pub/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.
 
 /// Generic utility functions. Stuff that should possibly be in core.
 library utils;
 
 import 'dart:async';
 import 'dart:crypto';
 import 'dart:isolate';
 import 'dart:uri';
 
 /// A pair of values.
 class Pair<E, F> {
   E first;
   F last;
 
   Pair(this.first, this.last);
 
   String toString() => '($first, $last)';
 
   bool operator==(other) {
     if (other is! Pair) return false;
     return other.first == first && other.last == last;
   }
 
   int get hashCode => first.hashCode ^ last.hashCode;
 }
 
+/// A completer that waits until all added [Future]s complete.
+// TODO(rnystrom): Copied from web_components. Remove from here when it gets
+// added to dart:core. (See #6626.)
+class FutureGroup<T> {
+  int _pending = 0;
+  Completer<List<T>> _completer = new Completer<List<T>>();
+  final List<Future<T>> futures = <Future<T>>[];
+  bool completed = false;
+
+  final List<T> _values = <T>[];
+
+  /// Wait for [task] to complete.
+  Future<T> add(Future<T> task) {
+    if (completed) {
+      throw new StateError("The FutureGroup has already completed.");
+    }
+
+    _pending++;
+    futures.add(task.then((value) {
+      if (completed) return;
+
+      _pending--;
+      _values.add(value);
+
+      if (_pending <= 0) {
+        completed = true;
+        _completer.complete(_values);
+      }
+    }).catchError((e) {
+      if (completed) return;
+
+      completed = true;
+      _completer.completeError(e.error, e.stackTrace);
+    }));
+
+    return task;
+  }
+
+  Future<List> get future => _completer.future;
+}
+
 // TODO(rnystrom): Move into String?
 /// Pads [source] to [length] by adding spaces at the end.
 String padRight(String source, int length) {
   final result = new StringBuffer();
   result.add(source);
 
   while (result.length < length) {
     result.add(' ');
   }
 
@@ skipping 130 matching lines @@
 
 /// Add all key/value pairs from [source] to [destination], overwriting any
 /// pre-existing values.
 void mapAddAll(Map destination, Map source) =>
   source.forEach((key, value) => destination[key] = value);
 
 /// Decodes a URL-encoded string. Unlike [decodeUriComponent], this includes
 /// replacing `+` with ` `.
 String urlDecode(String encoded) =>
   decodeUriComponent(encoded.replaceAll("+", " "));