Apollo Server Upper Case Directive

uppercase-directive.js

const { 
  ApolloServer,
  gql,
  SchemaDirectiveVisitor 
} = require('apollo-server');
const { defaultFieldResolver } = require('graphql');

const typeDefs = gql`
  directive @upper on FIELD_DEFINITION

  type Query {
    hello: String @upper
  }
`

const resolvers = {
  Query: {
    hello: () => 'world'
  }
};

class UpperCaseDirective extends SchemaDirectiveVisitor {
  visitFieldDefinition(field) {
    const { resolve = defaultFieldResolver } = field;
    field.resolve = async function(...args) {
      const result = await resolve.apply(this, args);
      if (typeof result === 'string') {
        return result.toUpperCase();
      }
      return result;
    };
  }
}

const server = new ApolloServer({
  typeDefs,
  resolvers,
  schemaDirectives: {
    upper: UpperCaseDirective,
    upperCase: UpperCaseDirective
  }
});

server.listen().then(({ url }) => {
  console.log(`Server ready at ${url}`);
});