Custom Directives

As of @graphql-tools version 8, the mechanism for defining and applying custom directives has changed significantly, and this is reflected in the Neo4j GraphQL Library.

It comes highly recommended to read and follow the @graphql-tools documentation on schema directives for comprehensive documentation on this feature.

Example

This example will work towards the implementation of a field directive to uppercase field values, with the following definition:

directive @uppercase on FIELD_DEFINITION

As per the @graphql-tools documentation, a function will be created which returns both the definition and the transformer which provides the behaviour:

function upperDirective(directiveName: string) {
    return {
        upperDirectiveTypeDefs: `directive @${directiveName} on FIELD_DEFINITION`,
        upperDirectiveTransformer: (schema: GraphQLSchema) =>
            mapSchema(schema, {
                [MapperKind.OBJECT_FIELD]: (fieldConfig) => {
                    const fieldDirective = getDirective(schema, fieldConfig, directiveName)?.[0];
                    if (fieldDirective) {
                        const { resolve = defaultFieldResolver } = fieldConfig;
                        fieldConfig.resolve = async (source, args, context, info) => {
                            const result = await resolve(source, args, context, info);
                            if (typeof result === "string") {
                                return result.toUpperCase();
                            }
                            return result;
                        };
                    }
                    return fieldConfig;
                },
            }),
    };
}

On calling the function, the type definition and the transformer will be returned for the directive:

const { upperDirectiveTypeDefs, upperDirectiveTransformer } = upperDirective("uppercase");

On construction of a Neo4jGraphQL instance, the directive definition can be passed into the typeDefs array alongside the rest of the type definitions:

const neoSchema = new Neo4jGraphQL({
    typeDefs: [
        upperDirectiveTypeDefs,
        `#graphql
            type Movie {
                name: String @uppercase
            }
        `,
    ],
    driver,
});

Finally, the Neo4j GraphQL schema must be transformed using the transformer returned from the directive function:

const schema = upperDirectiveTransformer(await neoSchema.getSchema());

This schema object is an instance of a GraphQLSchema which can be used in any GraphQL tools, such as in Apollo Server.