Add a schema-level hook for lazy/batched resolution

[rmosolgo]

GraphQL-Ruby's lazy-resolve system is OK, but it has a high overhead without much benefit from its generality. Most of the time, a schema has only one type of lazy object (batch-loader or graphql-batch), and the rest of the time, all the method lookup stuff is overcomplicated and a waste of time.

So, what if we exposed some schema-level methods that could be overridden as needed? In fact, we've already done this in GitHub as a performance consideration (we overrode #lazy_method_name).

TODO:

• test that overriding works

cc @exAspArk

[exAspArk]

👍

Just as an idea, here is how I personally imagine API could look like:

class PostType < GraphQL::Schema::Object
  field :id, ID, null: false
  field :comments, [CommentType], null: true, lazy: true
  #                                           ^
  # an explicit flag, no more matching by predefined classes to detect lazy objects
  # duck typing, yay!
end

class Schema < GraphQL::Schema
  query QueryType

  def lazy_resolve(value)                # or any other new API method with a default implementation, can be overridden
    case value
    when MyBatchClass
      value.sync                         # existing behavior, sort of
    else
      value.resolve_all if value.quacks? # custom behavior if necessary
    end
  end
end

• Potentially no breaking changes
• Can still support different lazy classes and methods within a schema
• Can be extended to detect lazy objects not only by class

[rmosolgo]

@exAspArk , I think the difference between the code on this branch is the addition of lazy: true, is that right?

I don't think I want to add field-level opting in, because we have various execution wrappers that may or may not wrap eager values in lazy objects. So, it can be hard to know which fields return lazy values under which conditions!