uniqueDirectiveNamesRule function

Visitor uniqueDirectiveNamesRule(SDLValidationCtx context)

Unique directive names

A GraphQL document is only valid if all defined directives have unique names.

See https://spec.graphql.org/draft/#sec-Schema

Implementation

Visitor uniqueDirectiveNamesRule(
  SDLValidationCtx context,
) {
  final knownDirectiveNames = <String, NameNode>{};
  final schema = context.schema;

  return TypedVisitor()
    ..add<DirectiveDefinitionNode>((node) {
      final directiveName = node.name.value;

      if (schema?.getDirective(directiveName) != null) {
        context.reportError(
          GraphQLError(
            'Directive "@${directiveName}" already exists in the schema.'
            ' It cannot be redefined.',
            locations: [
              GraphQLErrorLocation.fromSourceLocation(node.name.span!.start),
            ],
            extensions: _uniqueDirectiveNamesSpec.extensions(),
          ),
        );
        return null;
      }

      final previous = knownDirectiveNames[directiveName];
      if (previous != null) {
        context.reportError(
          GraphQLError(
            'There can be only one directive named "@${directiveName}".',
            locations: [
              GraphQLErrorLocation.fromSourceLocation(previous.span!.start),
              GraphQLErrorLocation.fromSourceLocation(node.name.span!.start),
            ],
            extensions: _uniqueDirectiveNamesSpec.extensions(),
          ),
        );
      } else {
        knownDirectiveNames[directiveName] = node.name;
      }

      return VisitBehavior.skipTree;
    });
}