Add support for Flutter SDK constraints.

lib/src/lock_file.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.
 
 import 'dart:collection';
 
 import 'package:path/path.dart' as p;
 import 'package:package_config/packages_file.dart' as packages_file;
 import 'package:pub_semver/pub_semver.dart';
 import 'package:source_span/source_span.dart';
 import 'package:yaml/yaml.dart';
 
 import 'io.dart';
 import 'package.dart';
 import 'source_registry.dart';
 import 'system_cache.dart';
 import 'utils.dart';
 
 /// A parsed and validated `pubspec.lock` file.
 class LockFile {
   /// The packages this lockfile pins.
   final Map<String, PackageId> packages;
 
-  /// The intersection of all SDK constraints for all locked packages.
-  final VersionConstraint sdkConstraint;
+  /// The intersection of all Dart SDK constraints for all locked packages.
+  final VersionConstraint dartSdkConstraint;
+
+  /// The intersection of all Flutter SDK constraints for all locked packages,
+  /// or `null` if no packages require the Flutter SDK.
+  final VersionConstraint flutterSdkConstraint;
 
   /// Creates a new lockfile containing [ids].
   ///
-  /// If passed, [sdkConstraint] represents the intersection of all SKD
+  /// If passed, [dartSdkConstraint] represents the intersection of all Dart SDK
   /// constraints for all locked packages. It defaults to
-  /// [VersionConstraint.any].
-  LockFile(Iterable<PackageId> ids, {VersionConstraint sdkConstraint})
+  /// [VersionConstraint.any]. Similarly, [flutterSdkConstraint] represents the
+  /// intersection of all Flutter SDK constraints; however, it defaults to
+  /// `null`.
+  LockFile(Iterable<PackageId> ids, {VersionConstraint dartSdkConstraint,
+      VersionConstraint flutterSdkConstraint})
       : this._(
           new Map.fromIterable(
               ids.where((id) => !id.isRoot),
               key: (id) => id.name),
-          sdkConstraint ?? VersionConstraint.any);
+          dartSdkConstraint ?? VersionConstraint.any,
+          flutterSdkConstraint);
 
-  LockFile._(Map<String, PackageId> packages, this.sdkConstraint)
+  LockFile._(Map<String, PackageId> packages, this.dartSdkConstraint,
+      this.flutterSdkConstraint)
       : packages = new UnmodifiableMapView(packages);
 
   LockFile.empty()
       : packages = const {},
-        sdkConstraint = VersionConstraint.any;
+        dartSdkConstraint = VersionConstraint.any,
+        flutterSdkConstraint = null;
 
   /// Loads a lockfile from [filePath].
   factory LockFile.load(String filePath, SourceRegistry sources) {
     return LockFile._parse(filePath, readTextFile(filePath), sources);
   }
 
   /// Parses a lockfile whose text is [contents].
   factory LockFile.parse(String contents, SourceRegistry sources) {
     return LockFile._parse(null, contents, sources);
   }
 
   /// Parses the lockfile whose text is [contents].
   ///
   /// [filePath] is the system-native path to the lockfile on disc. It may be
   /// `null`.
   static LockFile _parse(String filePath, String contents,
       SourceRegistry sources) {
     if (contents.trim() == '') return new LockFile.empty();
 
     var sourceUrl;
     if (filePath != null) sourceUrl = p.toUri(filePath);
     var parsed = loadYamlNode(contents, sourceUrl: sourceUrl);
 
     _validate(parsed is Map, 'The lockfile must be a YAML mapping.', parsed);
 
-    var sdkConstraint = VersionConstraint.any;
-    var sdkConstraintText = parsed['sdk'];
-    if (sdkConstraintText != null) {
+    var dartSdkConstraint = VersionConstraint.any;
+    VersionConstraint flutterSdkConstraint;
+    var sdkNode = parsed.nodes['sdk'];
+    if (sdkNode != null) {
+      // Lockfiles produced by pub versions from 1.14.0 through 1.18.0 included
+      // a top-level "sdk" field which encoded the unified constraint on the
+      // Dart SDK. They had no way of specifying constraints on other SDKs.
+      dartSdkConstraint = _parseVersionConstraint(sdkNode);
+    } else if ((parsed as Map).containsKey('sdks')) {
+      var sdksField = parsed['sdks'];
       _validate(
-          sdkConstraintText is String,
-          'The "sdk" field must be a string.',
-          parsed.nodes['sdk']);
+          sdksField is Map,
+          'The "sdks" field must be a mapping.',
+          parsed.nodes['sdks']);
 
-      sdkConstraint = _wrapFormatException(
-          'version constraint',
-          parsed.nodes['sdk'].span,
-          () => new VersionConstraint.parse(sdkConstraintText));
+      dartSdkConstraint = _parseVersionConstraint(sdksField.nodes['dart']);
+      flutterSdkConstraint =
+          _parseVersionConstraint(sdksField.nodes['flutter']);
     }
 
     var packages = {};
     var packageEntries = parsed['packages'];
     if (packageEntries != null) {
       _validate(packageEntries is Map, 'The "packages" field must be a map.',
           parsed.nodes['packages']);
 
       packageEntries.forEach((name, spec) {
         // Parse the version.
@@ skipping 21 matching lines @@
         }
 
         // Validate the name.
         _validate(name == id.name,
             "Package name $name doesn't match ${id.name}.", spec);
 
         packages[name] = id;
       });
     }
 
-    return new LockFile._(packages, sdkConstraint);
+    return new LockFile._(packages, dartSdkConstraint, flutterSdkConstraint);
+  }
+
+  /// Asserts that [node] is a version constraint, and parses it.
+  static VersionConstraint _parseVersionConstraint(YamlNode node) {
+    if (node == null) return null;
+
+    _validate(
+        node.value is String,
+        'Invalid version constraint: must be a string.',
+        node);
+
+    return _wrapFormatException(
+        'version constraint',
+        node.span,
+        () => new VersionConstraint.parse(node.value));
   }
 
   /// Runs [fn] and wraps any [FormatException] it throws in a
   /// [SourceSpanFormatException].
   ///
   /// [description] should be a noun phrase that describes whatever's being
   /// parsed or processed by [fn]. [span] should be the location of whatever's
   /// being processed within the pubspec.
   static _wrapFormatException(String description, SourceSpan span, fn()) {
     try {
@@ skipping 12 matching lines @@
 
   /// Returns a copy of this LockFile with [id] added.
   ///
   /// If there's already an ID with the same name as [id] in the LockFile, it's
   /// overwritten.
   LockFile setPackage(PackageId id) {
     if (id.isRoot) return this;
 
     var packages = new Map.from(this.packages);
     packages[id.name] = id;
-    return new LockFile._(packages, sdkConstraint);
+    return new LockFile._(packages, dartSdkConstraint, flutterSdkConstraint);
   }
 
   /// Returns a copy of this LockFile with a package named [name] removed.
   ///
   /// Returns an identical [LockFile] if there's no package named [name].
   LockFile removePackage(String name) {
     if (!this.packages.containsKey(name)) return this;
 
     var packages = new Map.from(this.packages);
     packages.remove(name);
-    return new LockFile._(packages, sdkConstraint);
+    return new LockFile._(packages, dartSdkConstraint, flutterSdkConstraint);
   }
 
   /// Returns the contents of the `.packages` file generated from this lockfile.
   ///
   /// If [entrypoint] is passed, a relative entry is added for its "lib/"
   /// directory.
   String packagesFile(SystemCache cache, [String entrypoint]) {
     var header = "Generated by pub on ${new DateTime.now()}.";
 
     var map = new Map.fromIterable(ordered(packages.keys), value: (name) {
@@ skipping 20 matching lines @@
       var description = package.source
           .serializeDescription(packageDir, package.description);
 
       packageMap[name] = {
         'version': package.version.toString(),
         'source': package.source.name,
         'description': description
       };
     });
 
-    var data = {'sdk': sdkConstraint.toString(), 'packages': packageMap};
+    var sdks = {
+      'dart': dartSdkConstraint.toString()
+    };
+    if (flutterSdkConstraint != null) {
+      sdks['flutter'] = flutterSdkConstraint.toString();
+    }
+
+    var data = {'sdks': sdks, 'packages': packageMap};
     return """
 # Generated by pub
 # See http://pub.dartlang.org/doc/glossary.html#lockfile
 ${yamlToString(data)}
 """;
   }
 }