[ruby-core:62467] [ruby-trunk - Feature #9781] Feature Proposal: Method#super_method

Issue #9781 has been updated by Josh Cheek.


I've only ever needed to do this in codebases like Rails, where there's an insane amount of inheritance. However, Rails also relies heavily on method_missing, which `super_method` would completely miss.

Anyway, I'd like this method to exist also.

Here's my crack at implementing it:

```
class Method
  def super_method
    receiver.singleton_class
            .ancestors
            .drop_while { |ancestor| ancestor != owner }
            .drop(1)
            .first
            .instance_method(name)
            .bind(receiver)
  rescue NameError
    raise NameError, "No super method `#{name}' for class `#{owner}'"
  end
end


class BigFoo
  def bar
  end
end

class Foo < Class.new(Class.new(Class.new(BigFoo)))
  def bar
  end
end

module MixinFoo 
  def bar
  end
end

Foo.new               # => #<Foo:0x007fc123148728>
   .extend(MixinFoo)  # => #<Foo:0x007fc123148728>
   .method(:bar)      # => #<Method: Foo(MixinFoo)#bar>
   .super_method      # => #<Method: Foo(Foo)#bar>
   .super_method      # => #<Method: Foo(BigFoo)#bar>
```

----------------------------------------
Feature #9781: Feature Proposal: Method#super_method
https://bugs.ruby-lang.org/issues/9781#change-46623

* Author: Richard Schneeman
* Status: Open
* Priority: Normal
* Assignee: 
* Category: core
* Target version: 
----------------------------------------

When `super` is called in a method the Ruby VM knows how to find the next ancestor that has that method and call it. It is difficult to do this manually, so I propose we expose this information in Method#super_location.

Ruby Method class (http://www.ruby-doc.org/core-2.1.1/Method.html) is returned by calling Object.method and passing in a method name (http://www.ruby-doc.org/core-2.1.1/Object.html#method-i-method). This is useful for debugging:

```ruby
# /tmp/code.rb
class Foo
  def bar
  end
end

puts Foo.new.method(:bar).source_location
# => ["/tmp/code.rb", 3]
```

The Object#method allows a ruby developer to easily track the source location of the method and makes debugging very easy. However if the code is being invoked by a call to `super` it is difficult to track down:

```ruby
# /tmp/code.rb

class BigFoo
  def bar
  end
end

class Foo < BigFoo
  def bar
    super
  end
end
```

In this code sample it is easy to find the method definition inside of Foo but it is very difficult in large projects to find what code exactly `super` is calling. This simple example is easy, but it can be hard when there are many ancestors. Currently if I wanted to find this we can inspect ancestors

```ruby
Foo.ancestors[1..-1].map do |ancestor|
  next unless ancestor.method_defined?(:bar)
  ancestor.instance_method(:bar)
end.compact.first.source_location
```

To make this process simpler I am proposing a method on the Method class that would return the result of `super`


It could be called like this:

```ruby
Foo.new.method(:bar).super_method
```

I believe adding Method#super_method, or exposing this same information somewhere else, could greatly help developers to debug large systems easily.




-- 
https://bugs.ruby-lang.org/