pure ruby scoped configuration files

configuration.rb provides a mechanism for configuring ruby programs with ruby configuration files. a configuration.rb file, for example ‘config/app.rb’, can be written simply as

Configuration.for('app') {
  key 'value'
  foo 'bar'
  port 42
}

and loaded via the normal ruby require/load mechanism

Kernel.load 'config/app.rb'

or with a slightly augmented loading mechnanism which simply searches an extra set of paths in addition to the standard ones

Configuration.path = %w( config configuration )

Configuration.load 'app'

configurations are completely open

Configuration.for('app') {
  object_id 'very open'
}

support arbitrarily nested values

Configuration.for('app') {
  a { b { c { d 42 } } }
}

c = Configuration.for 'app'

p c.a.b.c.d #=> 42

allow POLS scoped lookup of vars

Configuration.for('config') {
  outer 'bar'

  inner {
    value 42
  }
}

c = Configuration.for 'config'

p c.outer       #=> 'bar'
p c.inner.value #=> 42
p c.inner.outer #=> 'bar'

allow default values

default = Configuration.for( 'default' ) {
  a 1
  b 2
}

c = Configuration.for( 'config', default ) {
 a 10
}

p c.a     #=> 10
p c.b     #=> 2

and not a whole lot else - configuration.rb is s very small library consisting of one file and < 150 loc

~ > cat samples/a.rb

  #
  # basic usage is quite, simple, load the config and use it's values.  the
  # config syntax is fairly obvious, i think, but note that it *is* ruby and any
  # ruby can be included.  also note that each config is named, allowing
  # multiple configs to be places in one file
  #
    require 'configuration'

    c = Configuration.load 'a'

    p c.a + c.b - c.c

~ > ruby samples/a.rb

  42

~ > cat samples/b.rb

  #
  # configuration.rb supports a very natural nesting syntax.  note how values
  # are scoped in a POLS fashion
  #
    require 'configuration'

    c = Configuration.for 'b'

    p c.www.url
    p c.db.url
    p c.mail.url

~ > ruby samples/b.rb

  "http://codeforpeople.com:80"
  "db://codeforpeople.com:5342"
  "mail://gmail.com:25"

~ > cat samples/c.rb

  #
  # configuration.rb let's you keep code very dry.
  #

    require 'configuration'

    Configuration.load 'c'

    p Configuration.for('development').db
    p Configuration.for('production').db
    p Configuration.for('testing').db

~ > ruby samples/c.rb

  "db/development"
  "db/production"
  "db/testing"

~ > cat samples/d.rb

  #
  # configuration.rb makes use of an external blank slate dsl, this means that
  # you Configuration objects do, in fact, have all built-in ruby methods such
  # as #inspect, etc, *unless* you configure over the top of them.  the effect
  # is a configuration object that behaves like a nice ruby object, but which
  # allows *any* key to be configured
  #
    require 'configuration'

    c = Configuration.for 'd'

    p c.object_id
    p c.inspect
    p c.p

~ > ruby samples/d.rb

  config/d.rb:2:in `object_id': wrong number of arguments (1 for 0) (ArgumentError)
    from config/d.rb:2
    from ./lib/configuration.rb:159:in `instance_eval'
    from ./lib/configuration.rb:159:in `call'
    from ./lib/configuration.rb:159:in `method_missing'
    from ./lib/configuration.rb:105:in `evaluate'
    from ./lib/configuration.rb:68:in `initialize'
    from ./lib/configuration.rb:29:in `new'
    from ./lib/configuration.rb:29:in `for'
    from config/d.rb:1
    from ./lib/configuration.rb:53:in `load'
    from ./lib/configuration.rb:53:in `load'
    from ./lib/configuration.rb:31:in `for'
    from samples/d.rb:10

~ > cat samples/e.rb

  #
  # configuration.rb uses a totally clean slate dsl for the block.  if you need
  # to access base Object methods you can do this
  #

    require 'configuration'

    c = Configuration.for 'e'

    p c.foo
    p c.bar
    p c.foobar

~ > ruby samples/e.rb

  42
  "forty-two"
  42.0

~ > cat samples/f.rb

  #
  # configuration.rb let's you inherit values from another configuration.
  # Like this, you keep your code very dry.
  #

    require 'configuration'

    Configuration.load 'f'

    p c.a
    p c.b

~ > ruby samples/f.rb

  10
  2

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