Wie abbrechen ich Buildr anmutig?

Question

Ich betreiben Buildr in zwei verschiedenen Umgebungen (Windows XP und Linux) und deshalb habe ich lokale Java und Scala Installationen an verschiedenen Standorten. Ich habe die folgende Praxis zu überprüfen, dass die Umgebungsvariablen gesetzt sind:

require 'buildr/scala'
# Can I put these checks on a function ? How ?
ENV['JAVA_HOME'] ||= Buildr.settings.user['java_home']
if ENV['JAVA_HOME'].nil? then
  puts "Required environment variable JAVA_HOME was not set. Value can also be set in personal settings."
  Process.exit 1
end
puts 'JAVA_HOME = ' + ENV['JAVA_HOME']

ENV['SCALA_HOME'] ||= Buildr.settings.user['scala_home']
if ENV['SCALA_HOME'].nil? then
  puts "Required environment variable SCALA_HOME was not set. Value can also be set in personal settings."
  Process.exit 1
end
puts 'SCALA_HOME = ' + ENV['SCALA_HOME']

puts 'Scala version: ' + Scala.version

define "HelloWorld" do
  puts 'Hello World !'
end

Aber wie beende ich Buildr, so dass es mit dieser Art von Nachricht beendet:

Buildr aborted!
RuntimeError : Scala compiler crashed:
#<NullPointerException: unknown exception>
(See full trace by running task with --trace)

Soll ich eine Ausnahme aus (wenn ja, wie das in Ruby tun)?

Answer 1

Try fail:

if ENV['SCALA_HOME'].nil? then
  fail "Required environment variable SCALA_HOME was not set. Value can also be set in personal settings."
end

fail throws an exception in ruby. You might also see it called raise; they're equivalent. If you don't specify a type, the exception type will be RuntimeError as in your "compiler crashed" example.

Bonus answer: If you want to put these checks in a function (as your comment on the first one suggests), you can create a directory called tasks at the top level of your project, then put a file with a .rake extension in it. Define your functions there. Buildr will load all such files before evaluating your buildfile.

For example, you could have a file named tasks/helpers.rake with these contents:

def initialize_environment
  ENV['JAVA_HOME'] ||= Buildr.settings.user['java_home']
  unless ENV['JAVA_HOME']
    fail "Required environment variable JAVA_HOME was not set. Value can also be set in personal settings."
  end
  puts "JAVA_HOME = #{ENV['JAVA_HOME']}"
  # etc.
end

(Note: I changed a couple of other details — unless, string interpolation — to be more ruby-idomatic. The way you had it was fine, too, if you prefer that.)

Then at the top of your buildfile you could have this:

require 'buildr/scala'
initialize_environment
# etc.