Start pulling pub from its own repo.

sdk/lib/_internal/pub/lib/src/solver/version_selection.dart

Index: sdk/lib/_internal/pub/lib/src/solver/version_selection.dart
diff --git a/sdk/lib/_internal/pub/lib/src/solver/version_selection.dart b/sdk/lib/_internal/pub/lib/src/solver/version_selection.dart
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index c815f9f75ba62292dab7615a148f10d6cc8c1ae4..0000000000000000000000000000000000000000
--- a/sdk/lib/_internal/pub/lib/src/solver/version_selection.dart
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@@ -1,133 +0,0 @@
-// Copyright (c) 2015, 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.solver.version_selection;
-
-import 'dart:async';
-import 'dart:collection';
-
-import 'package:pub_semver/pub_semver.dart';
-
-import '../package.dart';
-import 'backtracking_solver.dart';
-import 'unselected_package_queue.dart';
-import 'version_solver.dart';
-
-/// A representation of the version solver's current selected versions.
-///
-/// This is used to track the joint constraints from the selected packages on
-/// other packages, as well as the set of packages that are depended on but have
-/// yet to be selected.
-///
-/// A [VersionSelection] is always internally consistent. That is, all selected
-/// packages are compatible with dependencies on those packages, no constraints
-/// are empty, and dependencies agree on sources and descriptions. However, the
-/// selection itself doesn't ensure this; that's up to the [BacktrackingSolver]
-/// that controls it.
-class VersionSelection {
-  /// The version solver.
-  final BacktrackingSolver _solver;
-
-  /// The packages that have been selected, in the order they were selected.
-  List<PackageId> get ids => new UnmodifiableListView<PackageId>(_ids);
-  final _ids = <PackageId>[];
-
-  /// Tracks all of the dependencies on a given package.
-  ///
-  /// Each key is a package. Its value is the list of dependencies placed on
-  /// that package, in the order that their dependers appear in [ids].
-  final _dependencies = new Map<String, List<Dependency>>();
-
-  /// A priority queue of packages that are depended on but have yet to be
-  /// selected.
-  final UnselectedPackageQueue _unselected;
-
-  /// The next package for which some version should be selected by the solver.
-  PackageRef get nextUnselected =>
-      _unselected.isEmpty ? null : _unselected.first;
-
-  VersionSelection(BacktrackingSolver solver)
-      : _solver = solver,
-        _unselected = new UnselectedPackageQueue(solver);
-
-  /// Adds [id] to the selection.
-  Future select(PackageId id) async {
-    _unselected.remove(id.toRef());
-    _ids.add(id);
-
-    // TODO(nweiz): Use a real for loop when issue 23394 is fixed.
-
-    // Add all of [id]'s dependencies to [_dependencies], as well as to
-    // [_unselected] if necessary.
-    await Future.forEach(await _solver.depsFor(id), (dep) async {
-      var deps = getDependenciesOn(dep.name);
-      deps.add(new Dependency(id, dep));
-
-      // If this is the first dependency on this package, add it to the
-      // unselected queue.
-      if (deps.length == 1 && dep.name != _solver.root.name) {
-        await _unselected.add(dep.toRef());
-      }
-    });
-  }
-
-  /// Removes the most recently selected package from the selection.
-  Future unselectLast() async {
-    var id = _ids.removeLast();
-    await _unselected.add(id.toRef());
-
-    for (var dep in await _solver.depsFor(id)) {
-      var deps = getDependenciesOn(dep.name);
-      deps.removeLast();
-
-      if (deps.isEmpty) {
-        _unselected.remove(dep.toRef());
-      }
-    }
-  }
-
-  /// Returns the selected id for [packageName].
-  PackageId selected(String packageName) =>
-      ids.firstWhere((id) => id.name == packageName, orElse: () => null);
-
-  /// Gets a "required" reference to the package [name].
-  ///
-  /// This is the first non-root dependency on that package. All dependencies
-  /// on a package must agree on source and description, except for references
-  /// to the root package. This will return a reference to that "canonical"
-  /// source and description, or `null` if there is no required reference yet.
-  ///
-  /// This is required because you may have a circular dependency back onto the
-  /// root package. That second dependency won't be a root dependency and it's
-  /// *that* one that other dependencies need to agree on. In other words, you
-  /// can have a bunch of dependencies back onto the root package as long as
-  /// they all agree with each other.
-  Dependency getRequiredDependency(String name) {
-    return getDependenciesOn(name)
-        .firstWhere((dep) => !dep.dep.isRoot, orElse: () => null);
-  }
-
-  /// Gets the combined [VersionConstraint] currently placed on package [name].
-  VersionConstraint getConstraint(String name) {
-    var constraint = getDependenciesOn(name)
-        .map((dep) => dep.dep.constraint)
-        .fold(VersionConstraint.any, (a, b) => a.intersect(b));
-
-    // The caller should ensure that no version gets added with conflicting
-    // constraints.
-    assert(!constraint.isEmpty);
-
-    return constraint;
-  }
-
-  /// Returns a string description of the dependencies on [name].
-  String describeDependencies(String name) =>
-      getDependenciesOn(name).map((dep) => "  $dep").join('\n');
-
-  /// Gets the list of known dependencies on package [name].
-  ///
-  /// Creates an empty list if needed.
-  List<Dependency> getDependenciesOn(String name) =>
-      _dependencies.putIfAbsent(name, () => <Dependency>[]);
-}