From: Vladimir Sizikov <vsizikov@...>
Date: 2008-07-28T05:30:05+09:00
Subject: [ruby-core:18002] Re: RUBY_ENGINE?

Hi,

On Sat, Jul 26, 2008 at 5:09 AM, Tanaka Akira <akr@fsij.org> wrote:
> I think
>
>  begin
>    require "zlib"
>  rescue LoadError
>    raise "no zlib"
>  end
>
> or
>
>  require "zlib"
>
> is much better becuase it works well with other engines if
> it provide zlib.

I agree, that in this case there is need for RUBY_ENGINE, but there
are other use cases when RUBY_ENGINE is much more preferable way. We
get constant flow of questions from users on how to detect the current
implementation.

One of the typical cases is Rails database config. JRuby uses
different drivers and slightly different configuration options, so
having a standard way to detect JRuby would be great. The same most
probably will be true for IronRuby, etc.
And sometimes users need to use different gems for different
implementations for various reasons. Begin-rescue is not the
best/performant way to do that.

Here's the example of rails database configuration:

if defined? JRUBY_VERSION
  gem 'activerecord-jdbc-adapter'
  require 'jdbc_adapter'
  adapter = 'jdbcmysql'
else
  adapter = 'mysql'
end

Add a couple more implementations with custom ways to detect them and
you have a mess.

Thanks,
  --Vladimir