JBuilder Arrays and non-collections

JBuilder may not be the most efficient way to present an API but for simple cases it works pretty well. Our JSON-API standardized API could return the current authenticated user like so.

show.json.jbuilder

json.data do
  json.id current_user.id
  json.type 'users'
  json.attributes do
    json.(current_user, :uuid, :email, :full_name)
  end
end

/api/v1/me

{
  "data": {
    "id": "1a2b3c4d000001",
    "type": "users",
    "attributes": {
      "uuid": "aaaaaaaabbbbbbbbccccccccc",
      "email": "rob.lacey@buttonmoon.co.uk",
      "full_name": "Mr Rob Lacey"
    }
 }

Ideally I want to now add an included block so that can included related objects such as Tenant. Something like

{
  "data": {
    "id": "1a2b3c4d000001",
    "type": "users",
    "attributes": {
      "uuid": "aaaaaaaabbbbbbbbccccccccc",
      "email": "rob.lacey@buttonmoon.co.uk",
      "full_name": "Mr Rob Lacey"
    },
    "included": [
      {
        "id": "1",
        "type": "tenants",
        "attributes": {
          "name": "superadmin"
        }
      }
    ]
  }
}

json.array! @comments do |comment|
  next if comment.marked_as_spam_by?(current_user)

  json.body comment.body
  json.author do
    json.first_name comment.author.first_name
    json.last_name comment.author.last_name
  end
end

json.array! @people, :id, :name

json.included do
  json.merge! do
    json.id current_user.tenant_id
    json.type 'tenants'
    json.attributes do
      json.(current_user.tenant, :name)
    end
  end
end

json.included [
  json.data do
    json.id current_user.tenant_id
    json.type 'tenants'
    json.attributes do
      json.(current_user.tenant, :name)
    end
  end
end
]

Neither of which work, turns out the way to do it is using the undocumented child! method.

json.data do
  json.id current_user.id
  json.type 'users'
  json.attributes do
    json.(current_user, :uuid, :email, :full_name)
  end

  json.included do
    json.child! do
      json.id current_user.tenant_id
      json.type 'tenants'
      json.attributes do
        json.(current_user.tenant, :name)
      end
    end
  end
end