@pothos/plugin-relay

Relay Plugin

The Relay plugin adds a number of builder methods a helper functions to simplify building a relay compatible schema.

Usage

Install

yarn add @pothos/plugin-relay

Setup

import RelayPlugin from '@pothos/plugin-relay';
const builder = new SchemaBuilder({
  plugins: [RelayPlugin],
  relayOptions: {
    // These will become the defaults in the next major version
    clientMutationId: 'omit',
    cursorType: 'String',
  },
});

Options

The relayOptions object passed to builder can contain the following properties:

• clientMutationId: required (default) | omit | optional. Determines if clientMutationId fields are created on relayMutationFields, and if they are required.
• cursorType: String | ID. Determines type used for cursor fields. Defaults behavior due to legacy reasons is String for everything except for connection arguments which use ID. Overwriting this default is highly encouraged.
• nodeQueryOptions: Options for the node field on the query object
• nodesQueryOptions: Options for the nodes field on the query object
• nodeTypeOptions: Options for the Node interface type
• pageInfoTypeOptions: Options for the TypeInfo object type
• clientMutationIdFieldOptions: Options for the clientMutationId field on connection objects
• clientMutationIdInputOptions: Options for the clientMutationId input field on connections fields
• mutationInputArgOptions: Options for the Input object created for each connection field
• cursorFieldOptions: Options for the cursor field on an edge object.
• nodeFieldOptions: Options for the node field on an edge object.
• edgesFieldOptions: Options for the edges field on a connection object.
• pageInfoFieldOptions: Options for the pageInfo field on a connection object.
• hasNextPageFieldOptions: Options for the hasNextPage field on the PageInfo object.
• hasPreviousPageFieldOptions: Options for the hasPreviousPage field on the PageInfo object.
• startCursorFieldOptions: Options for the startCursor field on the PageInfo object.
• endCursorFieldOptions: Options for the endCursor field on the PageInfo object.
• beforeArgOptions: Options for the before arg on a connection field.
• afterArgOptions: Options for the after arg on a connection field.
• firstArgOptions: Options for the first arg on a connection field.
• lastArgOptions: Options for the last arg on a connection field.

Global IDs

To make it easier to create globally unique ids the relay plugin adds new methods for creating globalID fields.

import { encodeGlobalID } from '@pothos/plugin-relay';

builder.queryFields((t) => ({
  singleID: t.globalID({
    resolve: (parent, args, context) => {
      return encodeGlobalID('SomeType', 123);
    },
  }),
  listOfIDs: t.globalIDList({
    resolve: (parent, args, context) => {
      return [{ id: 123, type: 'SomeType' }];
    },
  }),
}));

The returned IDs can either be a string (which is expected to already be a globalID), or an object with the an id and a type, The type can be either the name of a name as a string, or any object that can be used in a type parameter.

There are also new methods for adding globalIDs in arguments or fields of input types:

builder.queryType({
  fields: (t) => ({
    fieldThatAcceptsGlobalID: t.boolean({
      args: {
        id: t.arg.globalID({
          required: true,
        }),
        idList: t.arg.globalIDList(),
      },
      resolve(parent, args) {
        console.log(`Get request for type ${args.id.typename} with id ${args.id.id}`);
        return true;
      },
    }),
  }),
});

globalIDs used in arguments expect the client to send a globalID string, but will automatically be converted to an object with 2 properties (id and typename) before they are passed to your resolver in the arguments object.

Creating Nodes

To create objects that extend the Node interface, you can use the new builder.node method.

class NumberThing {
  id: number;

  binary: string;

  constructor(n: number) {
    this.id = n;
    this.binary = n.toString(2);
  }
}

builder.node(NumberThing, {
  // define an id field
  id: {
    resolve: (num) => num.id,
    // other options for id field can be added here
  },

  // Define only one of the following methods for loading nodes by id
  loadOne: (id) => new NumberThing(parseInt(id)),
  loadMany: (ids) => ids.map((id) => new NumberThing(parseInt(id))),
  loadWithoutCache: (id) => new NumberThing(parseInt(id)),
  loadManyWithoutCache: (ids) => ids.map((id) => new NumberThing(parseInt(id))),

  name: 'Number',
  fields: (t) => ({
    binary: t.exposeString('binary', {}),
  }),
});

builder.node will create an object type that implements the Node interface. It will also create the Node interface the first time it is used. The resolve function for id should return a number or string, which will be converted to a globalID. The relay plugin adds to new query fields node and nodes which can be used to directly fetch nodes using global IDs by calling the provided loadOne or laodMany method. Each node will only be loaded once by id, and cached if the same node is loaded multiple times inn the same request. You can provide loadWithoutCache or loadManyWithoutCache instead if caching is not desired, or you are already using a caching datasource like a dataloader.

Nodes may also implement an isTypeOf method which can be used to resolve the correct type for lists of generic nodes. When using a class as the type parameter, the isTypeOf method defaults to using an instanceof check, and falls back to checking the constructor property on the prototype. The means that for many cases if you are using classes in your type parameters, and all your values are instances of those classes, you won't need to implement an isTypeOf method, but it is usually better to explicitly define that behavior.

Creating Connections

The t.connection field builder method can be used to define connections. This method will automatically create the Connection and Edge objects used by the connection, and add before, after, first, and last arguments. The first time this method is used, it will also create the PageInfo type.

builder.queryFields((t) => ({
  numbers: t.connection(
    {
      type: NumberThing,
      resolve: (parent, { first, last, before, after }) => {
        return {
          pageInfo: {
            hasNextPage: false,
            hasPreviousPage: false,
            startCursor: 'abc',
            endCursor: 'def',
          },
          edges: [
            {
              cursor: 'abc',
              node: new NumberThing(123),
            },
            {
              cursor: 'def',
              node: new NumberThing(123),
            },
          ]
        }
      }),
    },
    {
      name: 'NameOfConnectionType', // optional, will use ParentObject + capitalize(FieldName) + "Connection" as the default
      fields: (tc) => ({
        // define extra fields on Connection
        // We need to use a new variable for the connection field builder (eg tc) to get the correct types
      }),
      // Other options for connection object can be added here
    },
    {
      // Same as above, but for the Edge Object
      name: 'NameOfEdgeType', // optional, will use Connection name + "Edge" as the default
      fields: (te) => ({
        // define extra fields on Edge
        // We need to use a new variable for the connection field builder (eg te) to get the correct types
      }),
    },
  ),
}));

Manually implementing connections can be cumbersome, so there are a couple of helper methods that can make resolving connections a little easier.

For limit/offset based apis:

import { resolveOffsetConnection } from '@pothos/plugin-relay';

builder.queryFields((t) => ({
  things: t.connection({
    type: SomeThings,
    resolve: (parent, args) => {
      return resolveOffsetConnection({ args }, ({ limit, offset }) => {
        return getThings(offset, limit);
      });
    },
  }),
}));

resolveOffsetConnection has a few default limits to prevent unintentionally allowing too many records to be fetched at once. These limits can be configure using the following options:

{
  args: ConnectionArguments;
  defaultSize?: number; // defaults to 20
  maxSize?: number; // defaults to 100
}

For APIs where you have the full array available you can use resolveArrayConnection, which works just like resolveOffsetConnection and accepts the same options.

import { resolveArrayConnection } from '@pothos/plugin-relay';

builder.queryFields((t) => ({
  things: t.connection({
    type: SomeThings,
    resolve: (parent, args) => {
      return resolveArrayConnection({ args }, getAllTheThingsAsArray());
    },
  }),
}));

Cursor based pagination can be implemented using the resolveCursorConnection method. The following example uses prisma, but a similar solution should work with any data store that supports limits, ordering, and filtering.

import { resolveCursorConnection, ResolveCursorConnectionArgs } from '@pothos/plugin-relay';

builder.queryField('posts', (t) =>
  t.connection({
    type: Post,
    resolve: (_, args) =>
      resolveCursorConnection(
        {
          args,
          toCursor: (post) => post.createdAt.toISOString(),
        },
        // Manually defining the arg type here is required
        // so that typescript can correctly infer the return value
        ({ before, after, limit, inverted }: ResolveCursorConnectionArgs) =>
          prisma.post.findMany({
            take: limit,
            where: {
              createdAt: {
                lt: before,
                gt: after,
              },
            },
            orderBy: {
              createdAt: inverted ? 'desc' : 'asc',
            },
          }),
      ),
  }),
);

Relay Mutations

You can use the relayMutationField method to define relay compliant mutation fields. This method will generate a mutation field, an input object with a clientMutationId field, and an output object with the corresponding clientMutationId.

Example ussage:

builder.relayMutationField(
  'deleteItem',
  {
    inputFields: (t) => ({
      id: t.id({
        required: true,
      }),
    }),
  },
  {
    resolve: async (root, args, ctx) => {
      if (ctx.items.has(args.input.id)) {
        ctx.items.delete(args.input.id);

        return { success: true };
      }

      return { sucess: false };
    },
  },
  {
    outputFields: (t) => ({
      sucess: t.boolean({
        resolve: (result) => result.success,
      }),
    }),
  },
);

Which produces the following graphql types:

input DeleteItemInput {
  clientMutationId: ID!
  id: ID!
}

type DeleteItemPayload {
  clientMutationId: ID!
  itWorked: Boolean!
}

type Mutation {
  deleteItem(input: DeleteItemInput!): DeleteItemPayload!
}

The relayMutationField has 4 arguments:

• name: Name of the mutation field
• inputOptions: Options for the input object
• fieldOptions: Options for the mutation field
• payloadOptions: Options for the Payload object

The inputOptions has a couple of non-standard options:

• name which can be used to set the name of the input object
• argName which can be used to overwrite the default arguments name (input).

The payloadOptions object also accepts a name property for setting the name of the payload object.

You can also access refs for the created input and payload objects so you can re-use them in other fields:

// Using aliases when destructuring lets you name your refs rather than using the generic `inputType` and `payloadType`
const { inputType: DeleteItemInput, payloadType: DeleteItemPayload } = builder.relayMutationField(
  'deleteItem',
  ...
);

Reusing connection objects

In some cases you may want to create a connection object type that is shared by multiple fields. To do this, you will need to create the connection object separately and then create a fields using a ref to your connection object:

import { resolveOffsetConnection } from '@pothos/plugin-relay';

const ThingsConnection = builder.connectionObject(
  {
    // connection options
    type: SomeThing,
    name: 'ThingsConnection',
  },
  {
    // Edge options (optional)
    name: 'ThingsEdge', // defaults to Appending `Edge` to the Connection name
  },
);

// You can use connection object with normal fields
builder.queryFields((t) => ({
  things: t.field({
    type: ThingsConnection,
    args: {
      ...t.arg.connectionArgs(),
    },
    resolve: (parent, args) => {
      return resolveOffsetConnection({ args }, ({ limit, offset }) => {
        return getThings(offset, limit);
      });
    },
  }),
}));

// Or by providing the connection type when creating a connection field
builder.queryFields((t) => ({
  things: t.connection({
    resolve: (parent, args) => {
      return resolveOffsetConnection({ args }, ({ limit, offset }) => {
        return getThings(offset, limit);
      });
    },
  }),
  ThingsConnection,
}));

builder.connectionObject creates the connect object type and the associated Edge type. t.arg.connectionArgs() will create the default connection args.

Reusing edge objects

Similarly you can directly create and re-use edge objects

import { resolveOffsetConnection } from '@pothos/plugin-relay';

const ThingsEdge = builder.edgeObject(
  {
    name: 'ThingsEdge',
    type: SomeThing,
  },
);

// The edge object can be used when creating a connection object
const ThingsConnection = builder.connectionObject(
  {
    type: SomeThing,
    name: 'ThingsConnection',
  },
  ThingsEdge,
);

// Or when creating a connection field
builder.queryFields((t) => ({
  things: t.connection({
    resolve: (parent, args) => {
      return resolveOffsetConnection({ args }, ({ limit, offset }) => {
        return getThings(offset, limit);
      });
    },
  }),
  {
    // connection options
  },
  ThingsEdge,
}));

builder.connectionObject creates the connect object type and the associated Edge type. t.arg.connectionArgs() will create the default connection args.

Expose nodes

The t.node and t.nodes methods can be used to add additional node fields. the expected return values of id and ids fields is the same as the resolve value of t.globalID, and can either be a globalID or an object with and an id and a type.

Loading nodes by id uses a request cache, so the same node will only be loaded once per request, even if it is used multiple times across the schema.

builder.queryFields((t) => ({
  extraNode: t.node({
    id: () => 'TnVtYmVyOjI=',
  }),
  moreNodes: t.nodeList({
    ids: () => ['TnVtYmVyOjI=', { id: 10, type: 'SomeType' }],
  }),
}));

decoding and encoding global ids

The relay plugin exports decodeGlobalID and encodeGlobalID as helper methods for interacting with global IDs directly. If you accept a global ID as an argument you can use the decodeGlobalID function to decode it:

builder.mutationFields((t) => ({
  updateThing: t.field({
    type: Thing,
    args: {
      id: t.args.id({ required: true }),
      update: t.args.string({ required: true }),
    },
    resolve(parent, args) {
      const { type, id } = decodeGlobalId(args.id);

      const thing = Thing.findById(id);

      thing.update(args.update);

      return thing;
    },
  }),
}));

Using custom encoding for global ids

In some cases you may want to encode global ids differently than the build in ID encoding. To do this, you can pass a custom encoding and decoding function into the relay options of the builder:

import RelayPlugin from '@pothos/plugin-relay';
const builder = new SchemaBuilder({
  plugins: [RelayPlugin],
  relayOptions: {
    encodeGlobalID: (typename: string, id: string | number | bigint) => `${typename}:${id}`,
    decodeGlobalID: (globalID: string) => {
      const [typename, id] = globalID.split(':');

      return { typename, id };
    },
  },
});

Extending all connections

There are 2 builder methods for adding fields to all connection objects: t.globalConnectionField and t.globalConnectionFields. These methods work like many of the other methods on the builder for adding fields to objects or interfaces.

builder.globalConnectionField('totalCount', (t) =>
  t.int({
    nullable: false,
    resolve: (parent) => 123,
  }),
);
// Or
builder.globalConnectionFields((t) => ({
  totalCount: t.int({
    nullable: false,
    resolve: (parent) => 123,
  }),
}));

In the above example, we are just returning a static number for our totalCount field. To make this more useful, we need to have our resolvers for each connection actually return an object that contains a totalCount for us. To guarantee that resolvers correctly implement this behavior, we can define custom properties that must be returned from connection resolvers when we set up our builder:

import RelayPlugin from '@pothos/plugin-relay';
const builder = new SchemaBuilder<{
  Connection: {
    totalCount: number;
  };
}>({
  plugins: [RelayPlugin],
  relayOptions: {},
});

Now typescript will ensure that objects returned from each connection resolver include a totalCount property, which we can use in our connection fields:

builder.globalConnectionField('totalCount', (t) =>
  t.int({
    nullable: false,
    resolve: (parent) => parent.totalCount,
  }),
);

Note that adding additional required properties will make it harder to use the provided connection helpers since they will not automatically return your custom properties. You will need to manually add in any custom props after getting the result from the helpers:

builder.queryFields((t) => ({
  posts: t.connection({
    type: Post,
    resolve: (parent, args, context) => {
      const postsArray = context.Posts.getAll();
      const result = resolveArrayConnection({ args }, postsArray);

      return result && { totalCount: postsArray.length, ...result };
    },
  }),
}));

Changing nullability of edges and nodes

If you want to change the nullability of the edges field on a Connection or the node field on an Edge you can configure this in 2 ways:

Globally

import RelayPlugin from '@pothos/plugin-relay';
const builder = new SchemaBuilder<{
  DefaultEdgesNullability: false;
  DefaultNodeNullability: true;
}>({
  plugins: [RelayPlugin],
  relayOptions: {
    edgesFieldOptions: {
      nullable: false,
    },
    nodeFieldOptions: {
      nullable: true,
    },
  },
});

The types provided for DefaultEdgesNullability and DefaultNodeNullability must match the values provided in the nullable option of edgesFieldOptions and nodeFieldOptions respectively. This will set the default nullability for all connections created by your builder.

nullability for edges fields defaults to { list: false, items: true } and the nullability of node fields default to false.

Per connection

builder.queryFields((t) => ({
  things: t.connection({
    type: SomeThings,
    edgesNullable: {
      items: true,
      list: false,
    },
    nodeNullable: false,
    resolve: (parent, args) => {
      return resolveOffsetConnection({ args }, ({ limit, offset }) => {
        return getThings(offset, limit);
      });
    },
  }),
}));
// Or

const ThingsConnection = builder.connectionObject({
  type: SomeThing,
  name: 'ThingsConnection',
  edgesNullable: {
    items: true,
    list: false,
  },
  nodeNullable: false,
});