GraphQL: How to handle referencing a type within its own type definition?

Question

Say I have the following:

type User {
  id: Int!
  name: String
  dob: String
  friends: [User]
}

Query {
  user(id: Int!): User
}

Looks to me like I just created the potential for infinite recursion:

query GetUser($userId: Int!) {
  user(id: $userId) {
    friends {
      name
      friends {
        name
        friends {
          name
          ...etc
        }
      }
    }

  }
}

How would I guard against this is in my user resolver?

It's not infinite recursion because your query only loads three nested levels, not an infinite number. Could you clarify what specifically are you concerned about? — loganfsmyth
– loganfsmyth, Commented Jun 15, 2021 at 16:43
usually max depth level/complexity cost is calculated/limited - not defined in type system at all - implementation related details — xadm
– xadm, Commented Jun 15, 2021 at 22:47

hp10 · Accepted Answer · 2021-06-18 12:38:46Z

1

This could be a potential problem, but you can use custom validation to prevent those kind of requests, e.g. https://github.com/stems/graphql-depth-limit

import depthLimit from 'graphql-depth-limit'
import express from 'express'
import graphqlHTTP from 'express-graphql'
import schema from './schema'

const app = express()

app.use('/graphql', graphqlHTTP((req, res) => ({
  schema,
  validationRules: [ depthLimit(10) ]
})))

answered Jun 18, 2021 at 12:38

hp10

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