Example for recursive object creation / reference fields

[ghost]

Could you please provide an example for a mutation that recursively creates an object? On the Drupal side we expect the "A" bundle to contain a field referencing the "B" bundle.

Expected usage from the GraphQL side:

type B {
  z: String
}
type A {
  b: B
}
input BInput {
  z: String
}
input AInput {
  b: BInput
}
mutation CreateA($a: AInput) {
  createA(a: $a) {
    id
    b {
      id
      z
    }
  }
}

Note that XXXInput has the exact same structure and types as XXX.

With $a = { b: { z: "example" } } it should return { id: 1234, b: { id: 3456, z: "example" } } (e.g.). In particular, A and B should be created as distinct Drupal nodes.

We already had a look at the following resources, but without finding examples for anything but the most simple cases:

• https://github.com/drupal-graphql/graphql/blob/8.x-3.x/README.md
• https://github.com/drupal-graphql/drupal-decoupled-app
• https://github.com/acquia-pso/decoupledkit-drupal
  • their documentation describes a case that appears similar to our use-case, but it also appears to be lacking any concrete examples or code
• https://github.com/pmelab/graphql-drupal-example
  • More complex in nature, but lacks mutations

[pmelab]

There is no way to do this automatically. You could use CreateEntityBase (as illustrated in https://www.amazeelabs.com/en/blog/extending-graphql-part-3-mutations) in for the host entity, but you have to create the nested entity manually (untested pseudocode):

protected function extractEntityInput(array $inputArgs, InputObjectType $inputType, ResolveInfo $info) {
  return [
    'b' => new B($inputArgs['b']).save(),
  ];
}

Or you could execute two mutations and look the nested entity up during creation of the host:

mutation CreateA($a: AInput) {
  createB(b: $b) {
    id
    z
  }
  createA(a: $a) {
    id
    b {
      id
      z
    }
  }
}

protected function extractEntityInput(array $inputArgs, InputObjectType $inputType, ResolveInfo $info) {
  return [
    'b' => B::lookupBbyZ($inputArgs['b']['z']),
  ];
}