Add Annotation#types, #vars, #methods

[vladfaust]

These methods would allow to iterate over all types/vars/methods which have the annotation, e.g:

annotation Foo
end

@[Foo]
class Bar
end

{% pp Foo.types %} # => [Bar]

/cc @Blacksmoke16, this could be useful in Athena, right?

I also can find it useful in ORM implementations.

[Blacksmoke16]

Yes, this would allow me to just get a list of all methods that are tagged as a route action. Currently I am requiring the controller classes to inherit from a predefined class, then iterating over the subclasses of that parent class, then filtering the methods down to just ones with the annotation.

This would be a bit cleaner, and allow the user to define their own inheritance structure.

[vladfaust]

@Blacksmoke16 there is an alternative possible solution for your case: https://forum.crystal-lang.org/t/type-all-includers/254

[Blacksmoke16]

@vladfaust What would your use case be for wanting an array of ALL methods/instance vars? Would it make more sense to do something like:

annotation Foo
end

class Klass
  @[Foo]
  def one
    1
  end
  
  @[Foo]
  def two
    2
  end

  def three
    3
  end
end

pp {{Klass.methods(Foo)}} # => [one, two]

Where allow methods/instance_vars on TypeNode to optionally takes an AnnotationType, and only returns methods/ivars with that annotation? This is already currently possible for methods, but would be still not be possible with ivars due to #7504 , would be for sure be cleaner.

[HertzDevil]

If #7648 (comment) works for types, do we still need this feature for instance / class variables and defs, or are there similar workarounds for them?

[Blacksmoke16]

@HertzDevil You can basically use the same workaround but with @type.methods. Only thing this feature would allow for is like getting an Array(Def) of all methods that have a given annotation irrespective of a specific type. However I'm not sure of how that would be useful/why you would need that.

[kalinon]

I also realized today that the workaround im used to using (Object.all_subclasses) misses any modules with annotations as well. (unless im missing a way to list modules)