leah blogs

(This blog post will go to ruby-talk as soon as Gmail fixes its SMTP.)

Hello,

During a discussion on IRC, I started to wonder if Ruby’s install scripts are state of the art, what could be done better and how.

Ruby’s mkmf.rb and Aoki’s setup.rb probably have their roots in the oldest pieces of Ruby source still in use. While setup.rb had some changes in the latter time, mkmf.rb more or less stayed the same.

I have looked into how other languages install source and compile extensions, and the library I liked best so far is Python’s distutils. I’m not very familiar with Python, but I like the general approach and the essence of API. Basically, you create a file, setup.py, like this:

from distutils.core import setup

setup (name = "Distutils",
       version = "0.1.1",
       description = "Python Module Distribution Utilities",
       author = "Greg Ward",
       author_email = "gward@python.net",
       url = "http://www.python.org/sigs/distutils-sig/",

       packages = ['distutils', 'distutils.command'])

In Ruby, this would maybe look like that:

require 'package'

setup {
  name "Distutils"
  version "0.1.1"
  description "Python Module Distribution Utilities"
  author "Greg Ward"
  author_email "gward@python.net"
  url "http://www.python.org/sigs/distutils-sig/"

  packages ['distutils', 'distutils/command']
}

Given this file, we can simply run:

python setup.py install

and the files will get installed where they belong to. distutils can also handle different prefixes, installing into home directories, and complex cases like putting scripts to /usr/bin, but libraries to /opt/local and whatever.

Python’s distutils also handles compiling extensions:

name = 'DateTime.mxDateTime.mxDateTime'
src = 'mxDateTime/mxDateTime.c'
setup (
  ...
  ext_modules =
    [(name,
     { 'sources': [src]
       'include_dirs': ['mxDateTime'] }
    )]
)

Here, something like this would be possible in Ruby (I’m not yet sure about exact semantics of the Python version):

setup {
  # ...
  extension("DateTime/mxDateTime/mxDateTime") {
    sources "mxDateTime/mxDateTime.c"
    include_dirs "mxDateTime"
  }
}

Of course, more complex build descriptions can be represented too:

extension("foolib") {
  sources "foo.c", "bar.c"
  if have_library("foo", "fooble")
    define "HAVE_FOO_H"
    cflags << `foo-config --cflags`
    ldflags << `foo-config --libs`
  else
    fail "foolib is needed"
  end
}

Whether this will generate a Makefile (like mkmf.rb), a Rakefile or compile directly (like distutils) is still an open question.

To allow for an easy conversion of setup.rb usage, Package will provide convenience methods that will make it behave like setup.rb with respect to the directory structure.

Package doesn’t try to conquer the world, however, it aims to be just a tool that would be useful if it was standard and everyone could build on due to it’s policy-neutrality

What advantages will Package have over setup.rb and mkmf.rb, as they are now?

• simple, clean and consistent working
• unified library to handle both extensions and libraries
• lightweight approach (if included in the standard library)
• easy adaption
• more flexible directory layout: especially small projects profit from this, as setup.rb’s directory layout is quite bulky by default and not very customizable
• easier packaging by third-party packagers due to simple but flexible and standardized invocation

What do we need to get a wide adoption of Package?

• inclusion in the standard library so it doesn’t need to be shipped with every package (as setup.rb unfortunately is).
• backing from the community to make use of Package.
• acceptance from packaging projects like RPA, RubyGems and distributions like Debian, FreeBSD and PLD.

Coding of Package has not started yet (the name is also not set into stone yet, so if you have better ideas, please tell me) because it would be pointless without a strong feedback from the community. I expect to get a first version done rather quickly, possibly borrowing code from setup.rb and mkmf.rb, but Package will not depend on these both. If anyone is interested in helping development, please mail me; helpful hands are always of use. Also, there will be need for testers on all and even the most weird platforms.

But now, I’ll ask you: Are you satisfied with the way installing Ruby extensions and libraries works? Do you think there is a place for Package? Do you have further improvements or can provide alternative ideas?

NP: Neil Young—My My, Hey Hey (Out Of The Blue)