GraphQL Error field type must be Input Type but got:

Here is the mutation:

const createNotebook = mutationWithClientMutationId ({
    name: 'CreateNotebook',
    inputFields: {
        token: {
            type: GraphQLString,
        },

        details: {
            type: NotebookDetails,
        },
    },
    outputFields: {

    },
    async mutateCRNotebook(input, context) {
        const data = getJSONFromRelativeURL(input.token);

    },
});

Here is the schema used in the details field of the mutation:

const NotebookDetails = new GraphQLObjectType({
    name: 'NotebookDetails',
    interfaces: [nodeInterface],

    fields: () => ({
        id: globalIdField('NotebookDetails'),

        description: {
            type: GraphQLString,
            description: '...',
            resolve(obj) {
                return obj.description;
            },
        },

        language: {
            type: GraphQLString,
            description: '...',
            resolve(obj) {
                return obj.language;
            },
        },

    }),

});

Error I am getting on running this code is :

api_1    | Error: CreateNotebookInput.details field type must be Input Type but got: NotebookDetails.
api_1    |     at invariant (/usr/src/app/node_modules/graphql/jsutils/invariant.js:19:11)
api_1    |     at /usr/src/app/node_modules/graphql/type/definition.js:698:58
api_1    |     at Array.forEach (native)
api_1    |     at GraphQLInputObjectType._defineFieldMap (/usr/src/app/node_modules/graphql/type/definition.js:693:16)
api_1    |     at GraphQLInputObjectType.getFields (/usr/src/app/node_modules/graphql/type/definition.js:682:49)
api_1    |     at typeMapReducer (/usr/src/app/node_modules/graphql/type/schema.js:224:26)
api_1    |     at typeMapReducer (/usr/src/app/node_modules/graphql/type/schema.js:190:12)
api_1    |     at Array.reduce (native)
api_1    |     at /usr/src/app/node_modules/graphql/type/schema.js:217:36
api_1    |     at Array.forEach (native)
api_1    |     at typeMapReducer (/usr/src/app/node_modules/graphql/type/schema.js:210:27)
api_1    |     at Array.reduce (native)
api_1    |     at new GraphQLSchema (/usr/src/app/node_modules/graphql/type/schema.js:98:34)
api_1    |     at Object.<anonymous> (/usr/src/app/src/schema/index.js:39:16)
api_1    |     at Module._compile (module.js:569:30)
api_1    |     at Object.Module._extensions..js (module.js:580:10)

I have used this syntax with queries and they worked correctly. But, they are returning error with a mutation. What is incorrect in my code and how do I correct it?

Answer

In GraphQL, an input cannot be used as a type and a type cannot be used as an input. Unfortunately, even if the fields appear identical to an existing type, you always have to define a separate input to use as an argument. Try something like this:

const NotebookDetailsInput = new GraphQLInputObjectType({
  name: 'NotebookDetailsInput',
  fields: () => ({
    id:          { type: GraphQLID },
    description: { type: GraphQLString },
    language:    { type: GraphQLString }, 
  })
});

If using SDL, the same type would look like this:

input {
  id: ID
  description: String
  language: String
}

Please see this answer for an extensive explanation of why it’s necessary to do this.

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Answer