Grape::Endpoint proxy scope breaks OOP inheritance

[kenaniah]

If my understanding is correct, when processing a request through grape, the request appears to be proxied using an anonymous instance of Grape::Endpoint, which breaks common assumptions of class inheritance.

For example:

class B < A
  get :action do 
    should_inherit # throws: NoMethodError (undefined method 'should_inherit' for <#<Class:0x...>:0x...>)
  end
end

class A < Grape::API
  def should_inherit
    "This should be available in class B when handling a request."
  end
end

When called from outside of the context of a grape API request, should_inherit resolves as expected. But when handling a request, a NoMethodError is thrown as the superclasses are not reflected in the ancestry chain of the anonymous Grape::Endpoint instance that is created to serve the request.

This presents an obvious "gotcha" when attempting to create a base class that all endpoints extend from without actually modifying the Grape::API class itself. I know it's possible to work around this issue by using modules and "helpers", but doing so is prohibitively verbose and violates the DRY principle when having to include them in every single endpoint.

If possible, could grape be modified to follow normal class inheritance when serving requests?

[dblock]

If you can make it work, we'd love a pull request! These classes act like singletons to avoid any state, that's something that was baked into grape a long, long time ago and I am pretty sure changing or fixing this has been attempted before.

[jackcasey]

I'll discuss 2 years later!

I find it really (really) hard to write DRY code in grape. I have a bunch of 'APIs' mounted alongside each other that all need the same helpers and same before and after blocks for logging, instrumentation, error handling etc and nothing works like it 'should' based on my (normal?) OOP assumptions. I don't even know if it's possible or not. Maybe I'm just being dense. But I end up with so much repeated code in each file that I just can't refactor into shared code. It's frustrating and makes me want to move from grape to something else.

But that said and rant over, I don't want to sound disparaging or ungrateful. I know this is kind of by design or at least by-original-design. Grape has served us well and open source libraries like grape are a privilege not a right and I'm thankful!

I guess I'm just flagging that to me the concept of no-surprise inheritance and OOP is important for a web server framework.

Cheers!