Is it possible to not return any data when using a GraphQL mutation?

(A) Solution with graphql-scalars

The original answer is below.

Here is another one solution with graphql-scalars library:

1. install npm install graphql-scalars and then
2. import their Void type: https://www.graphql-scalars.dev/docs/scalars/void

(B) Solution with a custom scalar

Note: design with void-result from mutations goes against "GQL best practices"

This example was written for NodeJS Apollo Framework, but it is pretty easy to convert the implementation for your language/framework

I'm pretty sure: there is an NPM-package named graphql-void but if you don't want to add another one dependency just copy this code.

1. define Void-scalar in your schema

# file: ./schema.gql

scalar Void

2. implement resolver

// file ./scalar-void.js

import { GraphQLScalarType } from 'graphql'

const Void = new GraphQLScalarType({
    name: 'Void',

    description: 'Represents NULL values',

    serialize() {
        return null
    },

    parseValue() {
        return null
    },

    parseLiteral() {
        return null
    }
})
export Void

3. add the resolver to ApolloServer

Add the Void resolver to the options of your instance of Apollo Server:

# file: ./server.js

import { ApolloServer } from 'apollo-server-express'
import { Void } from './scalar-void'

const server = new ApolloServer({
    typeDefs,  // use your schema
    resolvers: {
        Void: Void,
        // ... your resolvers
    },
    
})

4. use Void for your mutations in the schema

Finally, use the new scalar in your schema:

# file: ./schema.gql

type Mutation{
    addElement(element: ElementData): ID
    removeElement(id: ID): Void
}

According to this Github issue you cannot return nothing.

You can define a return type which is nullable e.g.

type Mutation {
  addElement(element: ElementData): ID
  removeElement(id: ID): Boolean
}

But I suggest you return the id of the deleted element, because if you want to work with a cached store you have to update the store when the delete mutation has ran successfully.

If you use TypeScript and graphql-codegen:

• In the GraphQL schema:

  scalar Void
  
  type Mutation {
    removeElement(id: ID): Void
  }
  

• In the codegen config for resolvers:

  config:
    scalars:
      Void: "void"
  

With this config TypeScript will ensure that nothing is returned from the removeElement mutation resolver. And the returning value for the mutation will always be null on the GraphQL side.

Check out graphql-scalars Void. This is standard boilerplate for all of my GraphQL projects.

npm i graphql-scalars