Rewrite the pkg/yaml parser.

pkg/yaml/lib/src/yaml_node.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.
 
 library yaml.yaml_node;
 
 import 'dart:collection' as collection;
 
 import 'package:collection/collection.dart';
 import 'package:source_span/source_span.dart';
 
 import 'null_span.dart';
+import 'style.dart';
 import 'yaml_node_wrapper.dart';
 
 /// An interface for parsed nodes from a YAML source tree.
 ///
 /// [YamlMap]s and [YamlList]s implement this interface in addition to the
 /// normal [Map] and [List] interfaces, so any maps and lists will be
 /// [YamlNode]s regardless of how they're accessed.
 ///
 /// Scalars values like strings and numbers, on the other hand, don't have this
 /// interface by default. Instead, they can be accessed as [YamlScalar]s via
 /// [YamlMap.nodes] or [YamlList.nodes].
 abstract class YamlNode {
   /// The source span for this node.
   ///
   /// [SourceSpan.message] can be used to produce a human-friendly message about
   /// this node.
-  SourceSpan get span;
+  SourceSpan get span => _span;
+
+  SourceSpan _span;
 
   /// The inner value of this node.
   ///
   /// For [YamlScalar]s, this will return the wrapped value. For [YamlMap] and
   /// [YamlList], it will return [this], since they already implement [Map] and
   /// [List], respectively.
   get value;
 }
 
 /// A read-only [Map] parsed from YAML.
 class YamlMap extends YamlNode with collection.MapMixin, UnmodifiableMapMixin  {
-  final SourceSpan span;
-
   /// A view of [this] where the keys and values are guaranteed to be
   /// [YamlNode]s.
   ///
   /// The key type is `dynamic` to allow values to be accessed using
   /// non-[YamlNode] keys, but [Map.keys] and [Map.forEach] will always expose
   /// them as [YamlNode]s. For example, for `{"foo": [1, 2, 3]}` [nodes] will be
   /// a map from a [YamlScalar] to a [YamlList], but since the key type is
   /// `dynamic` `map.nodes["foo"]` will still work.
   final Map<dynamic, YamlNode> nodes;
 
+  /// The style used for the map in the original document.
+  final CollectionStyle style;
+
   Map get value => this;
 
   Iterable get keys => nodes.keys.map((node) => node.value);
 
   /// Creates an empty YamlMap.
   ///
   /// This map's [span] won't have useful location information. However, it will
   /// have a reasonable implementation of [SourceSpan.message]. If [sourceUrl]
   /// is passed, it's used as the [SourceSpan.sourceUrl].
   ///
   /// [sourceUrl] may be either a [String], a [Uri], or `null`.
   factory YamlMap({sourceUrl}) =>
       new YamlMapWrapper(const {}, sourceUrl);
 
   /// Wraps a Dart map so that it can be accessed (recursively) like a
   /// [YamlMap].
   ///
   /// Any [SourceSpan]s returned by this map or its children will be dummies
   /// without useful location information. However, they will have a reasonable
   /// implementation of [SourceSpan.getLocationMessage]. If [sourceUrl] is
   /// passed, it's used as the [SourceSpan.sourceUrl].
   ///
   /// [sourceUrl] may be either a [String], a [Uri], or `null`.
   factory YamlMap.wrap(Map dartMap, {sourceUrl}) =>
       new YamlMapWrapper(dartMap, sourceUrl);
 
   /// Users of the library should not use this constructor.
-  YamlMap.internal(Map<dynamic, YamlNode> nodes, this.span)
-      : nodes = new UnmodifiableMapView<dynamic, YamlNode>(nodes);
+  YamlMap.internal(Map<dynamic, YamlNode> nodes, SourceSpan span, this.style)
+      : nodes = new UnmodifiableMapView<dynamic, YamlNode>(nodes) {
+    _span = span;
+  }
 
   operator [](key) {
     var node = nodes[key];
     return node == null ? null : node.value;
   }
 }
 
 // TODO(nweiz): Use UnmodifiableListMixin when issue 18970 is fixed.
 /// A read-only [List] parsed from YAML.
 class YamlList extends YamlNode with collection.ListMixin {
-  final SourceSpan span;
+  final List<YamlNode> nodes;
 
-  final List<YamlNode> nodes;
+  /// The style used for the list in the original document.
+  final CollectionStyle style;
 
   List get value => this;
 
   int get length => nodes.length;
 
   set length(int index) {
     throw new UnsupportedError("Cannot modify an unmodifiable List");
   }
 
   /// Creates an empty YamlList.
@@ skipping 12 matching lines @@
   /// Any [SourceSpan]s returned by this list or its children will be dummies
   /// without useful location information. However, they will have a reasonable
   /// implementation of [SourceSpan.getLocationMessage]. If [sourceUrl] is
   /// passed, it's used as the [SourceSpan.sourceUrl].
   ///
   /// [sourceUrl] may be either a [String], a [Uri], or `null`.
   factory YamlList.wrap(List dartList, {sourceUrl}) =>
       new YamlListWrapper(dartList, sourceUrl);
 
   /// Users of the library should not use this constructor.
-  YamlList.internal(List<YamlNode> nodes, this.span)
-      : nodes = new UnmodifiableListView<YamlNode>(nodes);
+  YamlList.internal(List<YamlNode> nodes, SourceSpan span, this.style)
+      : nodes = new UnmodifiableListView<YamlNode>(nodes) {
+    _span = span;
+  }
 
   operator [](int index) => nodes[index].value;
 
   operator []=(int index, value) {
     throw new UnsupportedError("Cannot modify an unmodifiable List");
   }
 }
 
 /// A wrapped scalar value parsed from YAML.
 class YamlScalar extends YamlNode {
-  final SourceSpan span;
+  final value;
 
-  final value;
+  /// The style used for the scalar in the original document.
+  final ScalarStyle style;
 
   /// Wraps a Dart value in a [YamlScalar].
   ///
   /// This scalar's [span] won't have useful location information. However, it
   /// will have a reasonable implementation of [SourceSpan.message]. If
   /// [sourceUrl] is passed, it's used as the [SourceSpan.sourceUrl].
   ///
   /// [sourceUrl] may be either a [String], a [Uri], or `null`.
   YamlScalar.wrap(this.value, {sourceUrl})
-      : span = new NullSpan(sourceUrl);
+      : style = ScalarStyle.ANY {
+    _span = new NullSpan(sourceUrl);
+  }
 
   /// Users of the library should not use this constructor.
-  YamlScalar.internal(this.value, this.span);
+  YamlScalar.internal(this.value, SourceSpan span, this.style) {
+    _span = span;
+  }
 
   String toString() => value.toString();
 }
+
+/// Sets the source span of a [YamlNode].
+///
+/// This method is not exposed publicly.
+void setSpan(YamlNode node, SourceSpan span) {
+  node._span = span;
+}