GraphQL [graphql js] circular dependencies: The type of * must be Output Type but got: [object Object]

问题

EDIT

added my solution as an answer

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ORIGINAL QUESTION

i believe this issue has to do with circular dependencies. i spent the better half of last night and today trying everything i could find online but nothing seems to work.

what i have tried:

• convert the fields prop to a function that returns a field object
• convert the relating fields (within the fields prop) into functions that return the type
• combining the two approaches above
• finally ending with require statements in place of the fields that use the reference type (does not seem correct and the linter had a stroke over this one)

here is the file structure:

here is the code:

userType.js

const graphql = require('graphql');
const Connection = require('../../db/connection');
const ConnectionType = require('../connection/connectionType');

const { GraphQLObjectType, GraphQLList, GraphQLString, GraphQLID } = graphql;

const UserType = new GraphQLObjectType({
  name: 'User',
  fields: () => ({
    id: { type: GraphQLID },
    username: { type: GraphQLString },
    email: { type: GraphQLString },
    created: {
      type: GraphQLList(ConnectionType),
      resolve: ({ id }) => Connection.find({ owner: id }),
    },
    joined: {
      type: GraphQLList(ConnectionType),
      resolve: ({ id }) => Connection.find({ partner: id }),
    },
  }),
});

module.exports = UserType;

connectionType.js

const graphql = require('graphql');
const User = require('../../db/user');
const UserType = require('../user/userType');

const { GraphQLObjectType, GraphQLString, GraphQLID, GraphQLInt } = graphql;

const ConnectionType = new GraphQLObjectType({
  name: 'Connection',
  fields: () => ({
    id: { type: GraphQLID },
    owner: {
      type: UserType,
      resolve: ({ owner }) => User.findById(owner),
    },
    partner: {
      type: UserType,
      resolve: ({ partner }) => User.findById(partner),
    },
    title: { type: GraphQLString },
    description: { type: GraphQLString },
    timestamp: { type: GraphQLString },
    lifespan: { type: GraphQLInt },
  }),
});

module.exports = ConnectionType;

回答1:

i couldnt get any help on this anywhere. in case anyone runs into this error message here are the steps i took to fix it:

1. switched from graphql-express to apollo-server-express (this was not necessary but i found apollo to be a more robust library)
2. used the following packages: graphql graphql-import graphql-tools
3. switched from javascript based Type defs to using the GraphQL SDL (.graphql) file type
4. step 3 is what corrected the circular import issue associated with one-to-many (and m2m) relationships

i committed every step of the refactor from dumping the old code to creating the new. i added plenty of notes and explicit naming so that it should be usable as a guide.

you can see the commit history diffs through the links below. all of the work until the last few commits was done within the graphql/ directory. if you click the title of the commit it will show you the diff so you can follow the refactor

• Last refactor with one-to-many relationship using apollo and GraphQL SDL Type defs
• commit history, start at Scrapped old GraphQL setup

after the refactor i now have cleaner resolvers, a better directory pattern, and, most importantly, fully functioning one-to-many relationships between User and Connection! ...only took my entire goddamn day.

the relationship in this case is: Connection belongs to an owner (User through owner_id) and partner (User through partner_id).

we will be moving forward from here with the codebase but i locked the branch and its commits for anyone who needs a guide.

回答2:

I had a similar issue using Typescript, and I kinda like the javascript based Type definition better so didn't change to GraphQL SDL.

I got it to work just by specifying the type of const to GraphQLObjectType.

Something like:

export const UserType: GraphQLObjectType = new GraphQLObjectType({
  name: 'UserType',
  fields: () => ({
    .....
  })
}

Now it works without a problem.

来源：https://stackoverflow.com/questions/50161256/graphql-graphql-js-circular-dependencies-the-type-of-must-be-output-type-bu