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

sdk/lib/_internal/pub_generated/lib/src/solver/version_solver.dart

Index: sdk/lib/_internal/pub_generated/lib/src/solver/version_solver.dart
diff --git a/sdk/lib/_internal/pub_generated/lib/src/solver/version_solver.dart b/sdk/lib/_internal/pub_generated/lib/src/solver/version_solver.dart
deleted file mode 100644
index d22ace779d7fa5f61b44329bb0f273a1d9861eac..0000000000000000000000000000000000000000
--- a/sdk/lib/_internal/pub_generated/lib/src/solver/version_solver.dart
+++ /dev/null
@@ -1,510 +0,0 @@
-// 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.
-
-library pub.solver.version_solver;
-
-import 'dart:async';
-import "dart:convert";
-
-import 'package:pub_semver/pub_semver.dart';
-import 'package:stack_trace/stack_trace.dart';
-
-import '../exceptions.dart';
-import '../lock_file.dart';
-import '../log.dart' as log;
-import '../package.dart';
-import '../pubspec.dart';
-import '../source_registry.dart';
-import '../utils.dart';
-import 'backtracking_solver.dart';
-import 'solve_report.dart';
-
-/// Attempts to select the best concrete versions for all of the transitive
-/// dependencies of [root] taking into account all of the [VersionConstraint]s
-/// that those dependencies place on each other and the requirements imposed by
-/// [lockFile].
-///
-/// If [useLatest] is given, then only the latest versions of the referenced
-/// packages will be used. This is for forcing an upgrade to one or more
-/// packages.
-///
-/// If [upgradeAll] is true, the contents of [lockFile] are ignored.
-Future<SolveResult> resolveVersions(SolveType type, SourceRegistry sources,
-    Package root, {LockFile lockFile, List<String> useLatest}) {
-  if (lockFile == null) lockFile = new LockFile.empty();
-  if (useLatest == null) useLatest = [];
-
-  return log.progress('Resolving dependencies', () {
-    return new BacktrackingSolver(
-        type,
-        sources,
-        root,
-        lockFile,
-        useLatest).solve();
-  });
-}
-
-/// The result of a version resolution.
-class SolveResult {
-  /// Whether the solver found a complete solution or failed.
-  bool get succeeded => error == null;
-
-  /// The list of concrete package versions that were selected for each package
-  /// reachable from the root, or `null` if the solver failed.
-  final List<PackageId> packages;
-
-  /// The dependency overrides that were used in the solution.
-  final List<PackageDep> overrides;
-
-  /// A map from package names to the pubspecs for the versions of those
-  /// packages that were installed, or `null` if the solver failed.
-  final Map<String, Pubspec> pubspecs;
-
-  /// The available versions of all selected packages from their source.
-  ///
-  /// Will be empty if the solve failed. An entry here may not include the full
-  /// list of versions available if the given package was locked and did not
-  /// need to be unlocked during the solve.
-  final Map<String, List<Version>> availableVersions;
-
-  /// The error that prevented the solver from finding a solution or `null` if
-  /// it was successful.
-  final SolveFailure error;
-
-  /// The number of solutions that were attempted before either finding a
-  /// successful solution or exhausting all options.
-  ///
-  /// In other words, one more than the number of times it had to backtrack
-  /// because it found an invalid solution.
-  final int attemptedSolutions;
-
-  final SourceRegistry _sources;
-  final Package _root;
-  final LockFile _previousLockFile;
-
-  /// Returns the names of all packages that were changed.
-  ///
-  /// This includes packages that were added or removed.
-  Set<String> get changedPackages {
-    if (packages == null) return null;
-
-    var changed = packages.where(
-        (id) =>
-            !_sources.idsEqual(
-                _previousLockFile.packages[id.name],
-                id)).map((id) => id.name).toSet();
-
-    return changed.union(
-        _previousLockFile.packages.keys.where(
-            (package) => !availableVersions.containsKey(package)).toSet());
-  }
-
-  SolveResult.success(this._sources, this._root, this._previousLockFile,
-      this.packages, this.overrides, this.pubspecs, this.availableVersions,
-      this.attemptedSolutions)
-      : error = null;
-
-  SolveResult.failure(this._sources, this._root, this._previousLockFile,
-      this.overrides, this.error, this.attemptedSolutions)
-      : this.packages = null,
-        this.pubspecs = null,
-        this.availableVersions = {};
-
-  /// Displays a report of what changes were made to the lockfile.
-  ///
-  /// [type] is the type of version resolution that was run.
-  void showReport(SolveType type) {
-    new SolveReport(type, _sources, _root, _previousLockFile, this).show();
-  }
-
-  /// Displays a one-line message summarizing what changes were made (or would
-  /// be made) to the lockfile.
-  ///
-  /// [type] is the type of version resolution that was run.
-  void summarizeChanges(SolveType type, {bool dryRun: false}) {
-    new SolveReport(
-        type,
-        _sources,
-        _root,
-        _previousLockFile,
-        this).summarize(dryRun: dryRun);
-  }
-
-  String toString() {
-    if (!succeeded) {
-      return 'Failed to solve after $attemptedSolutions attempts:\n' '$error';
-    }
-
-    return 'Took $attemptedSolutions tries to resolve to\n'
-        '- ${packages.join("\n- ")}';
-  }
-}
-
-/// Maintains a cache of previously-requested data: pubspecs and version lists.
-///
-/// Used to avoid requesting the same pubspec from the server repeatedly.
-class PubspecCache {
-  final SourceRegistry _sources;
-
-  /// The already-requested cached version lists.
-  final _versions = new Map<PackageRef, List<PackageId>>();
-
-  /// The errors from failed version list requests.
-  final _versionErrors = new Map<PackageRef, Pair<Object, Chain>>();
-
-  /// The already-requested cached pubspecs.
-  final _pubspecs = new Map<PackageId, Pubspec>();
-
-  /// The type of version resolution that was run.
-  final SolveType _type;
-
-  /// The number of times a version list was requested and it wasn't cached and
-  /// had to be requested from the source.
-  int _versionCacheMisses = 0;
-
-  /// The number of times a version list was requested and the cached version
-  /// was returned.
-  int _versionCacheHits = 0;
-
-  /// The number of times a pubspec was requested and it wasn't cached and had
-  /// to be requested from the source.
-  int _pubspecCacheMisses = 0;
-
-  /// The number of times a pubspec was requested and the cached version was
-  /// returned.
-  int _pubspecCacheHits = 0;
-
-  PubspecCache(this._type, this._sources);
-
-  /// Caches [pubspec] as the [Pubspec] for the package identified by [id].
-  void cache(PackageId id, Pubspec pubspec) {
-    _pubspecs[id] = pubspec;
-  }
-
-  /// Loads the pubspec for the package identified by [id].
-  Future<Pubspec> getPubspec(PackageId id) {
-    // Complete immediately if it's already cached.
-    if (_pubspecs.containsKey(id)) {
-      _pubspecCacheHits++;
-      return new Future<Pubspec>.value(_pubspecs[id]);
-    }
-
-    _pubspecCacheMisses++;
-
-    var source = _sources[id.source];
-    return source.describe(id).then((pubspec) {
-      _pubspecs[id] = pubspec;
-      return pubspec;
-    });
-  }
-
-  /// Returns the previously cached pubspec for the package identified by [id]
-  /// or returns `null` if not in the cache.
-  Pubspec getCachedPubspec(PackageId id) => _pubspecs[id];
-
-  /// Gets the list of versions for [package].
-  ///
-  /// Packages are sorted in descending version order with all "stable"
-  /// versions (i.e. ones without a prerelease suffix) before pre-release
-  /// versions. This ensures that the solver prefers stable packages over
-  /// unstable ones.
-  Future<List<PackageId>> getVersions(PackageRef package) {
-    if (package.isRoot) {
-      throw new StateError("Cannot get versions for root package $package.");
-    }
-
-    // See if we have it cached.
-    var versions = _versions[package];
-    if (versions != null) {
-      _versionCacheHits++;
-      return new Future.value(versions);
-    }
-
-    // See if we cached a failure.
-    var error = _versionErrors[package];
-    if (error != null) {
-      _versionCacheHits++;
-      return new Future.error(error.first, error.last);
-    }
-
-    _versionCacheMisses++;
-
-    var source = _sources[package.source];
-    return source.getVersions(
-        package.name,
-        package.description).then((versions) {
-      // Sort by priority so we try preferred versions first.
-      versions.sort(
-          _type == SolveType.DOWNGRADE ? Version.antiprioritize : Version.prioritize);
-
-      var ids =
-          versions.reversed.map((version) => package.atVersion(version)).toList();
-      _versions[package] = ids;
-      return ids;
-    }).catchError((error, trace) {
-      // If an error occurs, cache that too. We only want to do one request
-      // for any given package, successful or not.
-      log.solver("Could not get versions for $package:\n$error\n\n$trace");
-      _versionErrors[package] = new Pair(error, new Chain.forTrace(trace));
-      throw error;
-    });
-  }
-
-  /// Returns the previously cached list of versions for the package identified
-  /// by [package] or returns `null` if not in the cache.
-  List<PackageId> getCachedVersions(PackageRef package) => _versions[package];
-
-  /// Returns a user-friendly output string describing metrics of the solve.
-  String describeResults() {
-    var results = '''- Requested $_versionCacheMisses version lists
-- Looked up $_versionCacheHits cached version lists
-- Requested $_pubspecCacheMisses pubspecs
-- Looked up $_pubspecCacheHits cached pubspecs
-''';
-
-    // Uncomment this to dump the visited package graph to JSON.
-    //results += _debugWritePackageGraph();
-
-    return results;
-  }
-
-  /// This dumps the set of packages that were looked at by the solver to a
-  /// JSON map whose format matches the map passed to [testResolve] in the
-  /// version solver unit tests.
-  ///
-  /// If a real-world version solve is failing, this can be used to mirror that
-  /// data to build a regression test using mock packages.
-  String _debugDescribePackageGraph() {
-    var packages = {};
-    _pubspecs.forEach((id, pubspec) {
-      var deps = {};
-      packages["${id.name} ${id.version}"] = deps;
-
-      for (var dep in pubspec.dependencies) {
-        deps[dep.name] = dep.constraint.toString();
-      }
-    });
-
-    // Add in the packages that we know of but didn't need their pubspecs.
-    _versions.forEach((ref, versions) {
-      for (var id in versions) {
-        packages.putIfAbsent("${id.name} ${id.version}", () => {});
-      }
-    });
-
-    // TODO(rnystrom): Include dev dependencies and dependency overrides.
-
-    return JSON.encode(packages);
-  }
-}
-
-/// A reference from a depending package to a package that it depends on.
-class Dependency {
-  /// The name of the package that has this dependency.
-  final String depender;
-
-  /// The version of the depender that has this dependency.
-  final Version dependerVersion;
-
-  /// The package being depended on.
-  final PackageDep dep;
-
-  /// Whether [depender] is a magic dependency (e.g. "pub itself" or "pub global
-  /// activate").
-  bool get isMagic => depender.contains(" ");
-
-
-  Dependency(this.depender, this.dependerVersion, this.dep);
-
-  String toString() => '$depender $dependerVersion -> $dep';
-}
-
-/// An enum for types of version resolution.
-class SolveType {
-  /// As few changes to the lockfile as possible to be consistent with the
-  /// pubspec.
-  static const GET = const SolveType._("get");
-
-  /// Upgrade all packages or specific packages to the highest versions
-  /// possible, regardless of the lockfile.
-  static const UPGRADE = const SolveType._("upgrade");
-
-  /// Downgrade all packages or specific packages to the lowest versions
-  /// possible, regardless of the lockfile.
-  static const DOWNGRADE = const SolveType._("downgrade");
-
-  final String _name;
-
-  const SolveType._(this._name);
-
-  String toString() => _name;
-}
-
-/// Base class for all failures that can occur while trying to resolve versions.
-abstract class SolveFailure implements ApplicationException {
-  /// The name of the package whose version could not be solved.
-  ///
-  /// Will be `null` if the failure is not specific to one package.
-  final String package;
-
-  /// The known dependencies on [package] at the time of the failure.
-  ///
-  /// Will be an empty collection if the failure is not specific to one package.
-  final Iterable<Dependency> dependencies;
-
-  String get message => toString();
-
-  /// A message describing the specific kind of solve failure.
-  String get _message {
-    throw new UnimplementedError("Must override _message or toString().");
-  }
-
-  SolveFailure(this.package, Iterable<Dependency> dependencies)
-      : dependencies = dependencies != null ? dependencies : <Dependency>[];
-
-  String toString() {
-    if (dependencies.isEmpty) return _message;
-
-    var buffer = new StringBuffer();
-    buffer.write("$_message:");
-
-    var sorted = dependencies.toList();
-    sorted.sort((a, b) => a.depender.compareTo(b.depender));
-
-    for (var dep in sorted) {
-      buffer.writeln();
-      buffer.write("- ${log.bold(dep.depender)}");
-      if (!dep.isMagic) buffer.write(" ${dep.dependerVersion}");
-      buffer.write(" ${_describeDependency(dep.dep)}");
-    }
-
-    return buffer.toString();
-  }
-
-  /// Describes a dependency's reference in the output message.
-  ///
-  /// Override this to highlight which aspect of [dep] led to the failure.
-  String _describeDependency(PackageDep dep) =>
-      "depends on version ${dep.constraint}";
-}
-
-/// Exception thrown when the current SDK's version does not match a package's
-/// constraint on it.
-class BadSdkVersionException extends SolveFailure {
-  final String _message;
-
-  BadSdkVersionException(String package, String message)
-      : super(package, null),
-        _message = message;
-}
-
-/// Exception thrown when the [VersionConstraint] used to match a package is
-/// valid (i.e. non-empty), but there are no available versions of the package
-/// that fit that constraint.
-class NoVersionException extends SolveFailure {
-  final VersionConstraint constraint;
-
-  /// The last selected version of the package that failed to meet the new
-  /// constraint.
-  ///
-  /// This will be `null` when the failure occurred because there are no
-  /// versions of the package *at all* that match the constraint. It will be
-  /// non-`null` when a version was selected, but then the solver tightened a
-  /// constraint such that that version was no longer allowed.
-  final Version version;
-
-  NoVersionException(String package, this.version, this.constraint,
-      Iterable<Dependency> dependencies)
-      : super(package, dependencies);
-
-  String get _message {
-    if (version == null) {
-      return "Package $package has no versions that match $constraint derived "
-          "from";
-    }
-
-    return "Package $package $version does not match $constraint derived from";
-  }
-}
-
-// TODO(rnystrom): Report the list of depending packages and their constraints.
-/// Exception thrown when the most recent version of [package] must be selected,
-/// but doesn't match the [VersionConstraint] imposed on the package.
-class CouldNotUpgradeException extends SolveFailure {
-  final VersionConstraint constraint;
-  final Version best;
-
-  CouldNotUpgradeException(String package, this.constraint, this.best)
-      : super(package, null);
-
-  String get _message =>
-      "The latest version of $package, $best, does not match $constraint.";
-}
-
-/// Exception thrown when the [VersionConstraint] used to match a package is
-/// the empty set: in other words, multiple packages depend on it and have
-/// conflicting constraints that have no overlap.
-class DisjointConstraintException extends SolveFailure {
-  DisjointConstraintException(String package, Iterable<Dependency> dependencies)
-      : super(package, dependencies);
-
-  String get _message => "Incompatible version constraints on $package";
-}
-
-/// Exception thrown when two packages with the same name but different sources
-/// are depended upon.
-class SourceMismatchException extends SolveFailure {
-  String get _message => "Incompatible dependencies on $package";
-
-  SourceMismatchException(String package, Iterable<Dependency> dependencies)
-      : super(package, dependencies);
-
-  String _describeDependency(PackageDep dep) =>
-      "depends on it from source ${dep.source}";
-}
-
-/// Exception thrown when a dependency on an unknown source name is found.
-class UnknownSourceException extends SolveFailure {
-  UnknownSourceException(String package, Iterable<Dependency> dependencies)
-      : super(package, dependencies);
-
-  String toString() {
-    var dep = dependencies.single;
-    return 'Package ${dep.depender} depends on ${dep.dep.name} from unknown '
-        'source "${dep.dep.source}".';
-  }
-}
-
-/// Exception thrown when two packages with the same name and source but
-/// different descriptions are depended upon.
-class DescriptionMismatchException extends SolveFailure {
-  String get _message => "Incompatible dependencies on $package";
-
-  DescriptionMismatchException(String package,
-      Iterable<Dependency> dependencies)
-      : super(package, dependencies);
-
-  String _describeDependency(PackageDep dep) {
-    // TODO(nweiz): Dump descriptions to YAML when that's supported.
-    return "depends on it with description ${JSON.encode(dep.description)}";
-  }
-}
-
-/// Exception thrown when a dependency could not be found in its source.
-///
-/// Unlike [PackageNotFoundException], this includes information about the
-/// dependent packages requesting the missing one.
-class DependencyNotFoundException extends SolveFailure {
-  final PackageNotFoundException _innerException;
-  String get _message => "${_innerException.message}\nDepended on by";
-
-  DependencyNotFoundException(String package, this._innerException,
-      Iterable<Dependency> dependencies)
-      : super(package, dependencies);
-
-  /// The failure isn't because of the version of description of the package,
-  /// it's the package itself that can't be found, so just show the name and no
-  /// descriptive details.
-  String _describeDependency(PackageDep dep) => "";
-}