Allow access for attributes with reserved names via #[] (fixes #56)

[flash-gordon]

No description provided.

[solnic]

oh man, array + attribute lookup on each attr value read sounds not too good, perf-wise :/ Another thing is that now I can also see that public_send here was a mistake from the very beginning. I think it should always just do @attributes[name] or even @attributes.fetch(name)

[flash-gordon]

@solnic it's a set, which internally is implemented via a hash

[solnic]

@flash-gordon wdyt about leaving it as @attributes[name]? assuming we're OK with hash-like behavior, this would make perfect sense. I'm a bit "meh" when it comes to returning nil for attribute names that are not valid though...

[flash-gordon]

@solnic that's exactly the point. At the moment, there is no difference between calling methods and using #[], tbh I get used to this behavior but don't depend on it. After all, we can raise an error on accessing missing keys, it's not like hash behaves but does anyone care?

[solnic]

@flash-gordon right, so let's try @attributes.fetch(name), rescue KeyError and raise UnknownAttributeError or suttin. Sounds good?

[flash-gordon]

👍 will do

[paul]

Turns out, I was relying on this behavior for a project of mine. I'm using Dry::Struct to write a presenter library, and I was using it with Rails to generate urls. I had a superclass like this:

class Presenter < Dry::Struct
  transform_types { |t| t.meta(omittable: true) }
  attribute :url, Types::Url

  def url
    url_for(self)
  end
end

Then, subclasses could either override that method themselves, or when one presenter is calling another it could be passed in if needed, in case of nested routes.

class WidgetCollection < Presenter
  attribute :user_id, Types::Integer
  attribute :widgets, Types::Array

  def url
    user_widgets_path(user_id)
  end

  def widgets
    @widgets.map { |widget| WidgetPresenter.new(widget: widget, url: widget_path(user_id: user_id, widget) }
  end
end

Because it now uses #fetch instead of #public_send, I can no longer access "attributes" that are overridden by explicit methods. I also cannot use Types::URL.default { } because that block is eval'd in the class context rather than the instance (undefined method 'url_for' for Presenter:Class).

Any chance of rolling back this change? Should I open an issue? I can also just redefine the #[] method in my Presenter back to the old behavior.