Default nullability

By default, Pothos output fields are nullable, and arguments and input object fields are optional. Use nullable: false to make an output field non-null, or required: true to require an input.

You can change these defaults for a builder. Set each default in both the SchemaTypes generic for TypeScript checking and the constructor options for runtime schema generation:

import SchemaBuilder from '@pothos/core';

const builder = new SchemaBuilder<{
  DefaultFieldNullability: false;
  DefaultInputFieldRequiredness: true;
}>({
  defaultFieldNullability: false,
  defaultInputFieldRequiredness: true,
});

const GreetingInput = builder.inputType('GreetingInput', {
  fields: (t) => ({
    name: t.string(),
    title: t.string({ required: false }),
  }),
});

builder.queryType({
  fields: (t) => ({
    greeting: t.string({
      args: { input: t.arg({ type: GreetingInput }) },
      resolve: (_parent, { input }) =>
        `Hello, ${input.title ? `${input.title} ` : ''}${input.name}!`,
    }),
    nickname: t.string({ nullable: true, resolve: () => null }),
    names: t.stringList({ resolve: () => ['Ada'] }),
  }),
});

export const schema = builder.toSchema();

These settings are independent: omit the input setting from both places if you only want to change output nullability, or omit the output setting to change only input requiredness.

The example produces these field types:

input GreetingInput {
  name: String!
  title: String
}

type Query {
  greeting(input: GreetingInput!): String!
  names: [String!]!
  nickname: String
}

nullable: true and required: false override the new defaults on individual fields. List items remain non-null by default; changing the builder defaults controls the list itself. Use the object forms of nullable or required to configure items separately, as shown in Fields and Arguments.

{
  greeting(input: { name: "Ada" })
  names
  nickname
}

{
  "data": {
    "greeting": "Hello, Ada!",
    "names": ["Ada"],
    "nickname": null
  }
}

Changing defaults changes the public schema for fields without explicit settings. Requiring an existing optional argument or input field can break client requests. Non-null output fields also change error propagation: if a resolver returns null or throws, GraphQL propagates the null to the nearest nullable parent, potentially making the entire response's data null.