What does kind undefined mean here? I cannot find any solution for this error - api

Question

I am trying to split up my schema of GraphQL API into separate ones.
Having familiarized with a huge number of them I decided on this one below using "extend"
( I also wanted to use .graphql file extension for them but as I've got there is only one way to do that - it is with the use of webpack. I am not really good at it so I tried to make it work at first with .js files)
BUT: I cannot cope with this simple task because I either have TypeError: Cannot read property 'kind' of undefined or Invalid schema passed, or something else pops up...
What am I doing wrong here and what is the best practice/approach to split up and stitch the Schema?
Thanks in advance!
server.js
import express from "express";
import { ApolloServer, gql } from "apollo-server-express";
import { makeExecutableSchema } from 'graphql-tools';
import * as mongoClient from "./config";
import * as _ from 'lodash';
import { UserSchema, UserResolvers } from "./graphql.partials/user.api";
const port = process.env.PORT || 8080;
const RootSchema = gql`
type Query {
_empty: String
}
type Mutation {
_empty: String
}
`
const RootResolvers = {
};
const app = express();
const schema = makeExecutableSchema({
typeDefs: [RootSchema, UserSchema],
resolvers: _.merge(RootResolvers, UserResolvers)
});
const apolloServer = new ApolloServer({ schema });
apolloServer.applyMiddleware({ app });
app.listen({ port }, () => {
console.log(
`Server ready at http://localhost:${port}${apolloServer.graphqlPath}`
);
});
user schema
const { gql } = require("apollo-server-express");
import User from '../models/User';
export const typeDefs = gql`
extend type Query {
users: [User]
user(id: String): User
}
extend type Mutation {
addUser(email: String, password: String): User
deleteUser(id: String!): User
updateUser(user: UserInput): User
}
type User {
id: ID!
firstName: String
lastName: String
email: String!
password: String!
confirmed: Boolean
role: String
}
input UserInput {
id: ID!
firstName: String
lastName: String
email: String
password: String
confirmed: Boolean
role: String
}
`
export const UserResolvers = {
Query: {
users: async (obj, args, context, info) => {
try {
const res = await User.find();
return res;
} catch (err) {
return err.message;
}
},
user: async (obj, args, context, info) => {
try {
const res = User.findById(args['id']);
return res;
} catch (e) {
return e.message;
}
}
},
Mutation: {
addUser: async (obj, args, context, info) => {
try {
const res = await User.create(args);
return res;
} catch (err) {
return err.message;
}
},
deleteUser: async (obj, args, context, info) => {
try {
return User.findByIdAndDelete(args['id']);
} catch (e) {
return e.message;
}
},
updateUser: async (obj, args, context, info) => {
try {
return User.findByIdAndUpdate(args.user.id, args.user)
} catch (e) {
return e.message;
}
}
}
}

Answer 1

There is no export named UserSchema in your file. You have two named exports -- UserResolvers and typeDefs. As a result, when you attempt to import UserSchema, its value is undefined.