How do I set up GraphQL query so one or another argument is required, but not both

Question

I'm just getting to grips with GraphQL,

I have set up the following query: ​

type: UserType,
args: {
    id:    { name: 'id',    type: new GraphQLNonNull(GraphQLID)     },
    email: { name: 'email', type: new GraphQLNonNull(GraphQLString) }
},
resolve: (root, { id, email }, { db: { User } }, fieldASTs) => {
    ...
}

I would like to be able to pass either an 'id' or 'email' to the query, however, with this setup it requires both an id and email to be passed.

Is there a way to set up the query so only one argument is required, either id or email, but not both?

Answer 1

There's no built-in way to do that in GraphQL. You need to make your arguments nullable (by removing the GraphQLNonNull wrapper type from both of them) and then, inside your resolver, you can just do a check like:

resolve: (root, { id, email }, { db: { User } }, fieldASTs) => {
  if (!id && !email) return Promise.reject(new Error('Must pass in either an id or email'))
  if (id && email) return Promise.reject(new Error('Must pass in either an id or email, but not both.'))
  // the rest of your resolver
}