Graphql-ruby: Custom field class that uses `extras`, incompatible with `GraphQL::Relay::Node.field` as specified by `field:`?

[chrisbutcher]

Is there a way to customize all fields with custom extras for use with an extension? The recommended way in the guide conflicts with anyone using the field class option such as field :node, field: GraphQL::Relay::Node.field.

It also seems that even if someone is using add_field(NodeField) theres no way to set its extras.

class FieldWithExtensionAndExtras < GraphQL::Schema::Field
  def initialize(*args, **kwargs, &block)
    kwargs = kwargs.merge(extensions: [MyExtension])

    kwargs[:extras] ||= kwargs[:mutation]&.extras || []
    kwargs[:extras] << :ast_node # 💣

    super(*args, **kwargs, &block)
  end
end

class BaseObject < GraphQL::Schema::Object
  field_class FieldWithExtensionAndExtras
end

class Comment < BaseObject
  implements GraphQL::Relay::Node.interface
  description "A blog comment"

  field :id, ID, null: false
  field :body, String, null: false
end

class QueryRoot < BaseObject
  # NOTE: The following field definition, using `field:` errors out with:
  #   `ArgumentError: keyword `extras:` may only be used with method-based resolve and class-based field such as
  #   mutation class, please remove `field:`, `function:` or `resolve:``
  field :node, field: GraphQL::Relay::Node.field # 💥

  field :comments, [Comment], null: false
end

class Schema < GraphQL::Schema
  query QueryRoot
  use GraphQL::Analysis::AST
end

[rmosolgo]

Interesting! How about skipping the extras addition if kwargs[:field] is present? For example:

class FieldWithExtensionAndExtras < GraphQL::Schema::Field
  def initialize(*args, **kwargs, &block)
    kwargs = kwargs.merge(extensions: [MyExtension])
    if !kwargs[:field]
      kwargs[:extras] ||= kwargs[:mutation]&.extras || []
      kwargs[:extras] << :ast_node # 💣
    end 

    super(*args, **kwargs, &block)
  end
end

That would at least side-step it in this case! For a more fine-grained approach, you could add another initialization option to skip the extras, and pass the option when adding Node.field. What do you think?

[swalkinshaw]

Ideally we should be able to customize every field without skipping any like the above case. Skipping the legacy Node.field case seems fine, but I don't think there's any way to customize a field added by add_field either unless we're missing something.

We can't override add_field on object types and set extras because GraphQL::Schema::Field doesn't expose it like it does with extensions. So I think one solution is to forget about the Node.field case and add an #extras method to set extras after the field is instantiated.

[rmosolgo]

Is this more than an edge case? Why use add_field?

[swalkinshaw]

Isn't that the recommended solution to add the Node field now? It's used throughout the codebase when the new interpreter is used.

[rmosolgo]

Oh, you're using it just for the Node field, I see. Somehow I got the impression that there was more to it than that.

add an #extras method to set extras after the field is instantiated

Yeah, that seems fine!

[chrisbutcher]

I'd like to have a go at making this change :)

One small issue so far:

add an #extras method to set extras after the field is instantiated.

GraphQL::Schema::Field already has:

# @return [Array<Symbol>]
attr_reader :extras

Any opinions on whether we prefer to leave that attr_reader alone and sprout a new method to add extras to an instantiated field (add_extras?), or do we prefer to make extras behave similar to extensions?

def extras(new_extras = nil)
  if new_extras.nil?
    # Read the value
    @extras # returns [Array<Symbol>]
  else
    # ... @extras << ... etc.

[rmosolgo]

similar to extensions

:+1: