@ephys/graphql-non-null-directive

graphql-non-null-directive

Makes your GraphQL input optional, but not null!

The problem

GraphQL Thread from 2018

It's common for Update mutations to accept a partial input, in order to do a partial update.

The simplest version of this is to simply omit the non-nullish (!) operator in the input declaration, and not update anything that's nullish:

input UpdateUserInput {
  firstName: String
  lastName: String
  country: String
  # ...
}

The issue with this is that you lose the ability to say "if provided, this field cannot be null"

With a @nonNull directive, you get this ability back:

input UpdateUserInput {
  firstName: String @nonNull
  lastName: String @nonNull
  country: String
  # ...
}

Caveats

The @nonNull directive cannot be used on Argument Definitions. That is because, unlike in Object Inputs, GraphQL.js will always default optional arguments to null.

Instead of:

# this does not work!
type Mutation {
  updateUser(firstName: String @nonNull): User
}

Do:

# this works!
type Mutation {
  updateUser(input: UpdateUserInput!): User
}

input UpdateUserInput {
  firstName: String @nonNull
  # ...
}

Usage

*NB: This library is built using graphql-tools and should be compatible with apollo

• Install from npm: npm i @ephys/graphql-non-null-directive
• Declare the directive in your schema:

  directive @nonNull on INPUT_FIELD_DEFINITION

• Declare the directive in your Apollo Server:

  import { createNonNullDirective } from '@ephys/graphql-non-null-directive';
  
  const server = new ApolloServer({
    // ...
    schemaDirectives: { 
      nonNull: createNonNullDirective({
        // (optional) use this property to change the ID of the directive
        directiveName: 'nonNull',
        // (optional) use this property to configure how Input Errors are built
        //  Input Errors are thrown when a @nonNull input received null..
        buildInputError: (message: string) => {
          return new Error(message);
        },
      }),
    },
  });