Asp Forum - Ruby as a configuration language

jma

2/8/2007 3:51:00 PM

Hi

I'm writing an automated software building framework in Ruby. The software
compiles software packages from source code using human-written profiles. The
profiles should be extremely easy to read and write by humans (and easy to
parse by a program). I wish I could write the profiles in Ruby to avoid
creating yet another advanced configuration language. But... it seems that I
might not be able to do that. What I want is something like this:

# An example package description file. The actual building commands are
# written in a bash script.
name = "gcc"
version = "4.1.1"
title = " "GNU Compiler Collection"
description = "..."

archive {
localname = "#{name}-#{version}.tar.bz2"
originalname = "#{name}-#{version}.tar.gz"
baseurl "ftp://ftp.gnu.org...{version}/"
baseurl "ftp.mirror.site/gnu/gcc/#{version}/"
convert = "gz-bz2"
}

# Optional components
feature "gfortran" {
title = "Fortran compiler"
depend "gmp"
}

### END example

So my question is: is there a way to do this so that I would eval this package
description file and appropriate fields of internal objects would be filled
by the evaluated script?

Thanks in advance!

--
Tapio

8 Answers

Gavin Kistner

2/8/2007 4:33:00 PM

Tapio Kelloniemi wrote:
> I wish I could write the profiles in Ruby to avoid
> creating yet another advanced configuration language.

Some people will suggest YAML. That's certainly a reasonable way to
go. Don't create your own config language when a simple markup exists
that translates painlessly into Ruby data structures.

> # An example package description file. The actual building commands are
> # written in a bash script.
> name = "gcc"
> version = "4.1.1"
> title = " "GNU Compiler Collection"
> description = "..."
>
> archive {
> localname = "#{name}-#{version}.tar.bz2"
> originalname = "#{name}-#{version}.tar.gz"
> baseurl "ftp://ftp.gnu.org...{version}/"
> baseurl "ftp.mirror.site/gnu/gcc/#{version}/"
> convert = "gz-bz2"
> }
>
> # Optional components
> feature "gfortran" {
> title = "Fortran compiler"
> depend "gmp"
> }
>
> ### END example

If you want a true DSL, here's some untested code pointing you in the
right direction. I have no idea if you can have more than one archive,
or more than one feature, or more than one baseurl per Archive...but
you can do it.

class Archive
attr_accessor :localname, :originalname, :baseurl, :convert
end

class Feature
attr_accessor :title, :dependency
def depend( depends_on )
@dependency = depends_on
end
end

def archive( &block )
$archive = Archive.new
$archive.instance_eval( &block )
end

$features = []
def feature( &block )
f = Feature.new
$features << f
f.instance_eval( &block )
end

Simon Strandgaard

2/8/2007 4:35:00 PM

On 2/8/07, Tapio Kelloniemi <no@such.thing> wrote:
> I'm writing an automated software building framework in Ruby. The software
> compiles software packages from source code using human-written profiles. The
> profiles should be extremely easy to read and write by humans (and easy to
[snip]

There is a Ruby replacement of make, that can give you some
inspiration on how to do it. Perhaps rake can do all what you want?
http://rake.ruby...

--
Simon Strandgaard
http://opc...

Gavin Kistner

2/8/2007 4:40:00 PM

On Feb 8, 9:32 am, "Phrogz" <g...@refinery.com> wrote:
> Tapio Kelloniemi wrote:
> > archive {
> > localname = "#{name}-#{version}.tar.bz2"
> > originalname = "#{name}-#{version}.tar.gz"
> > baseurl "ftp://ftp.gnu.org...{version}/"
> > baseurl "ftp.mirror.site/gnu/gcc/#{version}/"
> > convert = "gz-bz2"
> > }
> class Archive
> attr_accessor :localname, :originalname, :baseurl, :convert
> end

Oops, I missed that baseurl was a method call there. Then you might
want something like:

class Archive
attr_accessor :localname, :originalname, :convert
def initialize
@baseurls = []
end
def baseurl( url )
@baseurls << url
end
end

Suraj Kurapati

2/8/2007 5:31:00 PM

Simon Strandgaard wrote:
> On 2/8/07, Tapio Kelloniemi <no@such.thing> wrote:
>> I'm writing an automated software building framework in Ruby. The software
>> compiles software packages from source code using human-written profiles. The
>> profiles should be extremely easy to read and write by humans (and easy to
> [snip]
>
> There is a Ruby replacement of make, that can give you some
> inspiration on how to do it. Perhaps rake can do all what you want?
> http://rake.ruby...

I agree. If you're going to build a DSL for your particular domain, I
suggest building it atop Rake. Stand on the shoulders of this jolly Red
giant.

--
Posted via http://www.ruby-....

Peter Booth

2/8/2007 5:56:00 PM

You should take a look at Capistrano - its pretty amazing what it does
out of the box, is base don Rake, and makes it easy to build, configure,
and deploy applications.

-----Original Message-----
From: Suraj Kurapati [mailto:snk@gna.org]
Sent: Thursday, February 08, 2007 12:31 PM
To: ruby-talk@ruby-lang.org
Subject: Re: Ruby as a configuration language

Simon Strandgaard wrote:
> On 2/8/07, Tapio Kelloniemi <no@such.thing> wrote:
>> I'm writing an automated software building framework in Ruby. The
>> software compiles software packages from source code using
>> human-written profiles. The profiles should be extremely easy to read

>> and write by humans (and easy to
> [snip]
>
> There is a Ruby replacement of make, that can give you some
> inspiration on how to do it. Perhaps rake can do all what you want?
> http://rake.ruby...

I agree. If you're going to build a DSL for your particular domain, I
suggest building it atop Rake. Stand on the shoulders of this jolly Red
giant.

--
Posted via http://www.ruby-....

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Brian Candler

2/8/2007 8:22:00 PM

On Fri, Feb 09, 2007 at 01:00:09AM +0900, Tapio Kelloniemi wrote:
> # An example package description file. The actual building commands are
> # written in a bash script.
> name = "gcc"
> version = "4.1.1"
> title = " "GNU Compiler Collection"
> description = "..."
>
> archive {
> localname = "#{name}-#{version}.tar.bz2"
> originalname = "#{name}-#{version}.tar.gz"
> baseurl "ftp://ftp.gnu.org...{version}/"
> baseurl "ftp.mirror.site/gnu/gcc/#{version}/"
> convert = "gz-bz2"
> }
>
> # Optional components
> feature "gfortran" {
> title = "Fortran compiler"
> depend "gmp"
> }
>
> ### END example

I did something a bit like this, using Rake, for building mail software. You
can download the source, which is basically just a bunch of package building
scripts, from http://linnet.ruby... (take the linnet-src package, or
check out from cvs)

You might be able to steal some ideas. It's not as abstracted as the way
you've described above, but I found in practice that the software packages I
was building didn't all fit into identical moulds.

jma

2/8/2007 9:54:00 PM

>I'm writing an automated software building framework in Ruby. The software
>compiles software packages from source code using human-written profiles. The
>profiles should be extremely easy to read and write by humans (and easy to
>parse by a program). I wish I could write the profiles in Ruby to avoid
>creating yet another advanced configuration language.

Thanks to all of you who responded. I thought that instance_eval would be the
solution, but I somehow overlooked it. Now I have to simulate scoping so that
code in archive and feature blocks may refer to things declared in the
top-level of the profile (which will not be real top-level, since the profile
scripts get inctance_evaled, to avoid pollution of Object). Overriding
method_missing probably solves this nicely.

Ruby is a great thing (although it lacks multiple dispatching and
multiple inheritance)!

--
Tapio

Joel VanderWerf

2/8/2007 10:31:00 PM

Tapio Kelloniemi wrote:
>> I'm writing an automated software building framework in Ruby. The software
>> compiles software packages from source code using human-written profiles. The
>> profiles should be extremely easy to read and write by humans (and easy to
>> parse by a program). I wish I could write the profiles in Ruby to avoid
>> creating yet another advanced configuration language.
>
> Thanks to all of you who responded. I thought that instance_eval would be the
> solution, but I somehow overlooked it. Now I have to simulate scoping so that
> code in archive and feature blocks may refer to things declared in the
> top-level of the profile (which will not be real top-level, since the profile
> scripts get inctance_evaled, to avoid pollution of Object). Overriding
> method_missing probably solves this nicely.
>
> Ruby is a great thing (although it lacks multiple dispatching and
> multiple inheritance)!

You could evaluate the whole config file inside of a scope (for example,
a module), and then pull objects out of this module as you need them.

There's one way to do this in:

http://redshift.sourceforge.n...

You can make methods like "archive" and "feature" available by
subclassing the Script module and defining them as module methods.

$ cat config-script.rb
name = "gcc"
version = "4.1.1"
title = "GNU Compiler Collection"
description = "..."

archive {
localname "#{name}-#{version}.tar.bz2"
#originalname "#{name}-#{version}.tar.gz"
#baseurl "ftp://ftp.gnu.org...{version}/"
#baseurl "ftp.mirror.site/gnu/gcc/#{version}/"
#convert "gz-bz2"
}

# Optional components
feature("gfortran") {
title "Fortran compiler"
#depend "gmp"
}

$ cat parser.rb
require 'script'

class Archive
def localname n; @localname = n; end
# etc.
end

class Feature
def initialize arg; @arg = arg; end
def title t; @title = t; end
# etc.
end

class ConfigScript < Script
def archive(&bl)
@archive = Archive.new
@archive.instance_eval(&bl)
end

def feature(arg, &bl)
@feature = Feature.new(arg)
@feature.instance_eval(&bl)
end

def inspect
super + [@archive, @feature].inspect
end
end

config_script = ConfigScript.load("config-script.rb")

p config_script

$ ruby parser.rb
#<ConfigScript:/home/vjoel/tmp/scr/config-script.rb>[#<Archive:0xb7cb5ff4
@localname="gcc-4.1.1.tar.bz2">, #<Feature:0xb7cb5f7c @arg="gfortran",
@title="Fortran compiler">]

This doesn't really try to solve your parsing questions. It's just an
example of how to eval the script inside a scope and not let that leak
out into the global scope.

It might be less work if you can accept a config file of the form:

$ cat config-script2.rb
NAME = "gcc"
VERSION = "4.1.1"
TITLE = "GNU Compiler Collection"
DESCRIPTION = "..."

ARCHIVE = {
:localname => "#{NAME}-#{VERSION}.tar.bz2"
}

module Features
GFORTRAN = {
:title => "Fortran compiler"
}
end

Then the parser is just:

$ cat parser2.rb
require 'script'

config_script = Script.load("config-script2.rb")

p config_script

p config_script::NAME

p config_script::ARCHIVE

config_script::Features.constants.each do |c|
p(c=>config_script::Features.const_get(c))
end

$ ruby parser2.rb
#<Script:/home/vjoel/tmp/scr/config-script2.rb>
"gcc"
{:localname=>"gcc-4.1.1.tar.bz2"}
{"GFORTRAN"=>{:title=>"Fortran compiler"}}

Anyway, I hope this suggests some of the possibilities for scoping your
DSL. There are lots of possibilities for sweetening up the syntax.

--
vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407

comp.lang.ruby

Ruby as a configuration language

jma

Gavin Kistner

Simon Strandgaard

Gavin Kistner

Suraj Kurapati

Peter Booth

Brian Candler

jma

Joel VanderWerf

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