GraphQL circular dependency JSON

Question

I am trying to pass an input object to a GraphQL object that looks like this:

input User {
    id: ID
    posts: [Post]
}
input Post {
    id: ID
    user: User
}

When pass an input object of type User which has a circular dependency with Post, I get a circular dependency error in the JSON.stringify call made during the fetch:

Converting circular structure to JSON
        --> starting at object with constructor 'User'
        |     property 'post' -> object with constructor 'Array'
        |     index 0 -> object with constructor 'Post'
        --- property 'user' closes the circle"

This issue is discussed here:

GraphQL circular dependency

The answer talks about changing the schema to use extend. However extend won’t work with input types. Is there another solution?

Please show your input type and mutation definition. I'm not sure how you could get this error unless your input type is `user > posts > user` — Michel Floyd, Aug 31 '23 at 21:21
the input types from the schema are listed above and yes user > posts > user. — jmc42, Sep 01 '23 at 09:20

score 0 · Answer 1 · answered Sep 01 '23 at 17:28

Your input types are over-specified. Input types do not need to match up with object types 1:1. In other words, you can have:

type User {
    id: ID
    name: String
    posts: [Post]
}
type: Post {
    id: ID
    body: String
    user: User
}

with input types:

input User {
    id: ID
    name: String
    posts: [Post]
}
input Post {
    id: ID
    body: String
}

There's no point in Post also specifying User data since you're starting from the User.

Although TBH you typically want to generate IDs on the server instead of passing them through a mutation.

GraphQL circular dependency JSON

1 Answers1