GraphQL variable combination validation

Question

Imagine the following (simplified) GraphQL schema:

type User {
  username: String
  email: String
}

type Query {
  user(username: String, email: String): User
}

If I would only want to allow querying user by giving a username, I would of course change it to user(username: String!), making the username required using the exclamation mark. Same thing vice versa with the email.

Is it possible though to have a GraphQL native solution where I validate for the existence of only either one (logical XOR) or at least one (logical OR) of the two input parameters?
Of course I could do it in the query resolver manually, but a @constraint directive like it is being used in Apollo GraphQL spreading across variables would be nice.

Ferran Buireu · Accepted Answer · 2021-03-03 07:53:48Z

1

Directly ... not possible:

check fields existence [within args] on resolver;
use @constraint to check each field shape;

Indirectly:

you can try to use union of input types:

.

type UserNameInput {
  username: String!
}
type UserEmailInput {
  email: String!
}
type UserInput = UserNameInput | UserEmailInput

type Query {
  user(input: UserInput): User
}

edited Mar 3, 2021 at 7:53

Ferran Buireu

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answered Feb 17, 2021 at 11:09

xadm

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