Cannot return null for non-nullable field

Question

I am trying to get some data with GraphQL by sending over a json web token but the result I get is an error.

This is the part of my resolvers, that is addressed by the error message.

const resolvers = {
    Query: {
        me: async (token) => {
            try {
                const payload = verify(token, process.env.SECRET);
                if (payload.userId) {
                    const me = await User.findById(payload.userId);
                    return me;
                } else {
                    throw { message: 'Invalid token!' };
                }
            } catch (error) {
                return error.message;
            }
        },

...

The error reads:

"errors": [
{
  "message": "Cannot return null for non-nullable field User.name.",
  "locations": [
    {
      "line": 3,
      "column": 5
    }
  ],
  "path": [
    "me",
    "name"
  ],
  "extensions": {
    "code": "INTERNAL_SERVER_ERROR",

...

The typeDef for user:

type User {
    id: ID!
    name: String!
    email: String!
    password: String!
}

and

extend type Query {
    me(token: String!): User
}

Where is my mistake!?

Thank you!

can you please share your typedef/schema for user for better debugging? — Shivanshu Gupta, Jun 15 '20 at 20:18
it's because in type User, you have marked all the fields mandatory in response. So, if one of the field is coming null or undefined from db, so graphql will throw error as it is a mandatory field and it is not present in response. — Shivanshu Gupta, Jun 15 '20 at 20:33
please verify payload.userId. Are you sure you are getting userId in this? — Shivanshu Gupta, Jun 15 '20 at 20:39

score 0 · Answer 1 · answered Jun 15 '20 at 20:58

0

const resolvers = {
    Query: {
        me: async (_, { token }) => {
            try {
                const payload = verify(token, process.env.SECRET);
                if (payload) {
                    const me = await User.findById(payload.userId);
                    return me;
                } else {
                    throw { message: 'Invalid token!' };
                }
            } catch (error) {
                return error.message;
            }
        }

...

this was the solution. I had (token) => { ... } but it should be (_, { token }) => { ... } in the me-function!

answered Jun 15 '20 at 20:58

Timo

21
6

You shouldn't return `error.message`. Just omit the catch, or if you want to obfuscate the original error, throw another error inside the catch. If you return a String or another non-error object, GraphQL will assume you're returning a User object and try to coerce the value accordingly. – Daniel Rearden Jun 15 '20 at 21:12
mmh, thanks for your advice. – Timo Jun 15 '20 at 21:15
but what should I replace the `error.message` with?!? – Timo Jun 15 '20 at 21:16
Just omit the try/catch – Daniel Rearden Jun 15 '20 at 21:58
thanks! :D now i am well prepared! – Timo Jun 15 '20 at 22:25

Cannot return null for non-nullable field

1 Answers1