anchor.diff:        ..add('version', version)
         ..add('homepage', homepage)
         ..add('documentation', documentation)
  +      ..add('environment', environment)
         ..add('description', description)
         ..add('dependencies', dependencies)
         ..add('dev_dependencies', devDependencies)
  
positive.code:   @override
    Map toJson() {
      return (buildJson
        ..add('sdk', sdkConstraint)
        ..addAll(unParsedYaml)).json;
    }
  }
  
negative.code:             ? documentation
              : this.documentation,
          description: description != null ? description : this.description,
          environment: environment != null ? environment : this.environment,
          dependencies: dependencies != null ? dependencies : this.dependencies,
          devDependencies: devDependencies != null
              ? devDependencies
  