Rendering scope method lookups

[viking]

If I have a View method called select, if I try to call select in the template, it calls Kernel#select instead of my view's select method.

The output of p method(:select) in the context of the template is:

#<Method: Lotus::View::Rendering::Scope(Kernel)#select>

[viking]

Is this a bug or intended?

[jodosha]

It looks like a bug.
Can you please add the code here to replicate the error?

On 11/ago/2014, at 18:23, Jeremy Stephens notifications@github.com wrote:

Is this a bug or intended?

—
Reply to this email directly or view it on GitHub.

[viking]

Added here: https://github.com/viking/view/commit/06ad81d570ebaefd0b63c19b9751b46246c0b6aa

[jodosha]

@viking This is an update after an extensive debugging session.

Lotus::View uses Template to wrap a Tilt::Template subclass: an instance of Tilt::ERBTemplate or Tilt::HamlTemplate.

Each subclass can override some methods to customize the behavior: eg #prepare.
For all them who don't override #evaluate(scope, locals, &block), they inherit it from the superclass.

This implementation wants concrete methods from the given scope, because it does some tricks by bounding and then unbounding methods to it. In other words, it doesn't send the #select message which is covered by Lotus::View::Rendering::Scope#method_missing, but it tries to "capture" the method and then invoke #call on it. See Method#call.

As proof of what I'm saying, add your failing test, and modify the source of Scope with:

def select
  'x'
end

It will invoke this method, instead of Kernel#select, because Scope now implements a concrete method.

/cc @judofyr

[judofyr]

It appears that Rendering::Scope uses method_missing to delegate method
calls to the view. However, Scope seems to inherit from Object (which
includes Kernel). Thus calling #select will never hit method_missing
because it is indeed defined somewhere in the ancestors of Scope.

There's two solutions: (1) Inherit from BasicObject instead. (2) Explicitly
undef_method which you don't want to have preference over method_missing.

// Magnus Holm

[jodosha]

@judofyr It works like a charm ✨ Thank you!

[viking]

Excellent. Thanks.