A repo that illustrate a bug in NestJS GraphQL
Hello, I think I found a bug in the GraphQL package. I'm not sure if it's caused by @nestjs/graphql or type-graphql, which Nest seems to be using under the hood.
I am using the code first approach.
The @Field() decorator can take an options object to configure the GraphQL property to be nullable or not and to have a default value or not.
TLDR: the defaultValue option explicitly makes the property nullable (regardless of the nullable option), even though null may not be an acceptable value in an input type.
@InputType()
export class CreateUserInput {
@Field((type) => [String], { nullable: false, defaultValue: [] })
details: string[];
}The previous code will generate the following schema.
input CreateUserInput {
details: [String!] = []
}This means that the values in the array must be non-null strings, that details has a default value of an empty array BUT details itself can be set to null.
This means that ALL the following mutations are valid but the last one should not. details should either be an array or not be present at all.
mutation CreateUser {
explicit: createUser(input: { details: ["Nest", "is", "so", "cool"] })
omitted: createUser(input: {})
explicitly_null: createUser(input: { details: null })
}Really, the typescript code above should produce the following schema (notice the TWO exclamation marks). Thus, the property does not accept null as an explicit value and uses the default value.
input CreateUserInput {
details: [String!]! = []
}What do you think ?