From: james@...
Date: 2015-11-02T23:13:31+00:00
Subject: [ruby-core:71301] [Ruby trunk - Feature #9696] More Flexible	Refinement Syntax

Issue #9696 has been updated by James Adam.


It *might* be possible to support both monkey-patching and refinements with a combination of modules, using prepend and refine:

~~~
class Target
end

# actual code
module Behaviour
  def new_method
    'facets-supplied behaviour'
  end
end
~~~

In 'facets/refinements.rb' you could define the following:

~~~
# refinement support
module Refinement
  refine Target do
    include Behaviour
  end
end
~~~

And then use it as follows:

~~~
require 'facets/refinements'
using Refinement
Target.new.new_method # => 'facets-supplied behaviour'
~~~

To use the same code via monkey-patching, use `prepend`; in 'facets/monkey-patch.rb':

~~~
# monkey-patch support
Target.send(:prepend, Behaviour)
~~~

And then to use it:

~~~
require 'facets/monkey-patch'
Target.new.new_method # => 'facets-supplied behaviour
~~~

Using `prepend` allows the module method definitions to take precedence over methods defined in the original class.

There's one significant problem doing this, which is that when you include a module via `refine`, methods in that module cannot call other methods within that module. I believe this is a simple artefact of the lexical scope of those method definitions, but it probably does make it impractical to use this technique for very sophisticated changes.

----------------------------------------
Feature #9696: More Flexible Refinement Syntax
https://bugs.ruby-lang.org/issues/9696#change-54673

* Author: Thomas Sawyer
* Status: Rejected
* Priority: Normal
* Assignee: 
----------------------------------------
I am the maintainer of Ruby Facets, the core extensions library. For the next release of Facets I have long planned to provide support for Refinements. Unfortunately, after working with the code to determine what would be necessary to support them, I've come to the conclusion that it's just not reasonable to do so. The problem lies in the fact that Facets must still be backward compatible with it's "monkey-patch" usage. In fact, that usage is sometimes preferable b/c you can require once and don't have to write `using Foo` in every file that a core extension might be needed. But, b/c of the syntax that refinements use, to support both patching and refining I would have to maintain TWO COPIES of every extension, which simply isn't practical.

For example, the normal definition of a String#foo:

~~~
class String
  def foo
    ...
  end
end
~~~

And the refinement:

~~~
module Facets
  refine String do
    def foo
      ...
    end
  end
end
~~~

There does not appear to be any reasonable way to have the definition defined once and still be able to be use it in either manner. (Also, I want to point out that refinements do not lend themselves to cherry picking specific methods per-file either.)

So, unless someone has a clever approach that I have not thought of, I wonder if it would not be a good idea to reconsider the syntax of refinements. Would it be possible to simplify the definition to use `class` instead of `refine`, e.g.

~~~
module Facets
  class String
    def foo
      ...
    end
  end
end
~~~

And then allow `using Facets` which would refine any common class is the scope. And further, allowing also `using Facets::String` and even `using Facets::String::foo` to cherry pick refinements? In addition, a way to "apply" a module as if it were evaluated in the scope. This would then allow the same code to be used either as a refinement or as an extension.

Alternatively, maybe refinements should just be a require --if they will forever remain at the file-level. Then no special syntax would be needed at all. Simply defining them in a separate file, e.g.

~~~
# string/foo.rb
class String
  def foo
    ...
  end
end
~~~

And then "using" them by file name instead would do the trick.

~~~
using 'string/foo'
~~~





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