Scalars

To add a custom scalar that has been implemented as GraphQLScalar from graphql-js you need to provide some type information in SchemaTypes generic parameter of the builder:

const builder = new SchemaBuilder<{
  Scalars: {
    Date: {
      Input: Date;
      Output: Date;
    };
  };
}>({});

builder.addScalarType('Date', CustomDateScalar, {});

The Input type is the type that will be used when when the type is used in an argument or InputObject. The Output type is used to validate the resolvers return the correct value when using the scalar in their return type.

const builder = new SchemaBuilder<{
  Scalars: {
    PositiveInt: {
      Input: number;
      Output: number;
    };
  };
}>({});

builder.scalarType('PositiveInt', {
  serialize: (n) => n,
  parseValue: (n) => {
    if (n >= 0) {
      return n;
    }

    throw new Error('Value must be positive');
  },
});

builder.queryFields((t) => ({
  date: t.field({
    type: 'Date',
    resolve: () => new Date(),
  }),

  positive: t.field({
    type: 'PositiveInt',
    resolve: () => 5,
  }),
}));