anchor.diff:    PSEntry? get url;
   }
   
  +/// Representation of a leaf-node from `pubspec.yaml`.
   abstract class PSNode {
     Source get source;
     SourceSpan get span;
  +
  +  /// String value of the node, or `null` if value in pubspec.yaml is `null` or
  +  /// omitted.
  +  ///
  +  /// **Example**
  +  /// ```
  +  /// name: foo
  +  /// version:
  +  /// ```
  +  /// In the example above the [PSNode] for `foo` will have [text] "foo", and
  +  /// the [PSNode] for `version` will have not have [text] as `null`, as empty
  +  /// value or `"null"` is the same in YAML.
     String? get text;
   }
   
  
positive.code:   }
    return PSEntry(
        _PSNode(key, resourceProvider), _PSNode(value, resourceProvider));
  }
  
  /// Representation of a key/value pair a map from package name to
  
negative.code:   return null;
  }
  
  PSEntry? _processScalar(
      YamlScalar key, YamlNode value, ResourceProvider? resourceProvider) {
    if (value is! YamlScalar) {
  