Various refactors in preparation for adding error reporting

lib/src/command_runner.dart

@@ -30,7 +30,6 @@ import 'http.dart';
 import 'io.dart';
 import 'log.dart' as log;
 import 'sdk.dart' as sdk;
-import 'solver.dart';
 import 'utils.dart';
 
 class PubCommandRunner extends CommandRunner {
@@ -232,12 +231,13 @@ and include the logs in an issue on https://github.com/dart-lang/pub/issues/new
   int _chooseExitCode(exception) {
     while (exception is WrappedException) exception = exception.innerError;
 
+    // TODO(nweiz): Emit an UNAVAILABLE exit code for a SolveFailure that was
+    // (transitively) caused by a package not existing.
     if (exception is HttpException ||
         exception is http.ClientException ||
         exception is SocketException ||
         exception is TlsException ||
-        exception is PubHttpException ||
-        exception is DependencyNotFoundException) {
+        exception is PubHttpException) {
       return exit_codes.UNAVAILABLE;
     } else if (exception is FormatException || exception is DataException) {
       return exit_codes.DATA;

lib/src/entrypoint.dart

@@ -214,8 +214,6 @@ class Entrypoint {
       }
     }
 
-    if (!result.succeeded) throw result.error;
-
     result.showReport(type);
 
     if (dryRun) {

lib/src/global_packages.dart

@@ -172,14 +172,11 @@ class GlobalPackages {
         dependencies: [dep], sources: cache.sources));
 
     // Resolve it and download its dependencies.
+    //
+    // TODO(nweiz): If this produces a SolveFailure that's caused by [dep] not
+    // being available, report that as a [dataError].
     var result = await resolveVersions(SolveType.GET, cache, root);
-    if (!result.succeeded) {
-      // If the package specified by the user doesn't exist, we want to
-      // surface that as a [DataError] with the associated exit code.
-      if (result.error.package != dep.name) throw result.error;
-      if (result.error is NoVersionException) dataError(result.error.message);
-      throw result.error;
-    }
+
     result.showReport(SolveType.GET);
 
     // Make sure all of the dependencies are locally installed.

lib/src/package_name.dart

@@ -102,8 +102,7 @@ class PackageRef extends PackageName {
   }
 
   String toTerseString() {
-    if (isMagic) return name;
-    if (isRoot || source.name != 'hosted') return "$name";
+    if (isMagic || isRoot || source.name == 'hosted') return name;
     return "$name from $source";
   }
 
@@ -157,8 +156,8 @@ class PackageId extends PackageName {
   }
 
   String toTerseString() {
-    if (isMagic) return name;
-    if (isRoot || source.name == 'hosted') return "$name $version";
+    if (isMagic || isRoot) return name;
+    if (source.name == 'hosted') return "$name $version";
     return "$name $version from $source";
   }
 }
@@ -230,8 +229,8 @@ class PackageRange extends PackageName {
   }
 
   String toTerseString() {
-    if (isMagic) return name;
-    if (isRoot || source.name == 'hosted') return "$name $constraint";
+    if (isMagic || isRoot) return name;
+    if (source.name == 'hosted') return "$name $constraint";
     return "$name $constraint from $source";
   }
 
@@ -242,6 +241,23 @@ class PackageRange extends PackageName {
         features: new Map.from(this.features)..addAll(features));
   }
 
+  /// Returns a copy of [this] with the same semantics, but with a `^`-style
+  /// constraint if possible.
+  PackageRange withTerseConstraint() {
+    if (constraint is! VersionRange) return this;
+    if (constraint.toString().startsWith("^")) return this;
+
+    var range = constraint as VersionRange;
+    if (range.includeMin &&
+        !range.includeMax &&
+        range.min != null &&
+        range.max == range.min.nextBreaking) {
+      return withConstraint(new VersionConstraint.compatibleWith(range.min));
+    } else {
+      return this;
+    }
+  }
+
   /// Whether [id] satisfies this dependency.
   ///
   /// Specifically, whether [id] refers to the same package as [this] *and*

lib/src/solver/failure.dart

@@ -2,201 +2,23 @@
 // 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.
 
-import 'dart:convert';
-
-import 'package:pub_semver/pub_semver.dart';
-import 'package:stack_trace/stack_trace.dart';
-
 import '../exceptions.dart';
-import '../log.dart' as log;
-import '../package_name.dart';
-import 'dependency.dart';
+import 'incompatibility.dart';
 
 /// 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.
+class SolveFailure implements ApplicationException {
+  /// The root incompatibility.
   ///
-  /// Will be an empty collection if the failure is not specific to one package.
-  final Iterable<Dependency> dependencies;
+  /// This will always indicate that the root package is unselectable. That is,
+  /// it will have one term, which will be the root package.
+  final Incompatibility incompatibility;
 
   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.name.compareTo(b.depender.name));
-
-    for (var dep in sorted) {
-      buffer.writeln();
-      buffer.write("- ${log.bold(dep.depender.name)}");
-      if (!dep.depender.isMagic && !dep.depender.isRoot) {
-        buffer.write(" ${dep.depender.version}");
-      }
-      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(PackageRange dep) {
-    var description = "depends on version ${dep.constraint}";
-    if (dep.features.isNotEmpty) description += " ${dep.featureDescription}";
-    return description;
+  SolveFailure(this.incompatibility) {
+    assert(incompatibility.terms.single.package.isRoot);
   }
-}
-
-/// 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)
-      : _message = message,
-        super(package, null);
-}
-
-/// 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(PackageRange 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.name} 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(PackageRange dep) {
-    // TODO(nweiz): Dump descriptions to YAML when that's supported.
-    return "depends on it with description ${JSON.encode(dep.description)}";
-  }
-}
-
-/// Exception thrown when a dependency could not be found in its source.
-///
-/// Unlike [PackageNotFoundException], this includes information about the
-/// dependent packages requesting the missing one.
-class DependencyNotFoundException extends SolveFailure
-    implements WrappedException {
-  final PackageNotFoundException innerError;
-  Chain get innerChain => innerError.innerChain;
-
-  String get _message => "${innerError.message}\nDepended on by";
-
-  DependencyNotFoundException(
-      String package, this.innerError, 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(PackageRange dep) => "";
-}
-
-/// An exception thrown when a dependency requires a feature that doesn't exist.
-class MissingFeatureException extends SolveFailure {
-  final Version version;
-  final String feature;
-
-  String get _message =>
-      "$package $version doesn't have a feature named $feature";
 
-  MissingFeatureException(String package, this.version, this.feature,
-      Iterable<Dependency> dependencies)
-      : super(package, dependencies);
+  // TODO(nweiz): Produce a useful error message.
+  String toString() => "Tough luck, Chuck!";
 }