<NME> gembag.rb
<BEF> #!/usr/bin/env ruby

# target for now
rubymajor = RUBY_VERSION.split(".")[0..1].join(".")
target = "#{Dir.pwd}/vendor/bundle/#{RUBY_ENGINE}/#{rubymajor}/"
ENV["GEM_HOME"] = target
ENV["GEM_PATH"] = ""

require "rubygems/specification"
require "rubygems/commands/install_command"

def install_gem(name, requirement, target)
  puts "Fetching and installing gem: #{name} (#{requirement})"

  installer = Gem::Commands::InstallCommand.new
  installer.options[:generate_rdoc] = false
  installer.options[:generate_ri] = false
  installer.options[:version] = requirement
  installer.options[:args] = [name]
  installer.options[:install_dir] = target
 
  # ruby 2.0.0 / rubygems 2.x; disable documentation generation
  installer.options[:document] = []
  begin
    installer.execute
  rescue Gem::SystemExitException => e
    if e.exit_code != 0
      puts "Installation of #{name} failed"
      raise
    end
  end
end # def install_gem

gemspec = ARGV.shift || "logstash-kafka.gemspec"

spec = Gem::Specification.load(gemspec)
deps = [spec.runtime_dependencies].flatten

deps.each do |dep|
  # TODO(sissel): Hack for now
  next if "#{dep}" == "addressable (~> 2.2.6)" 

  begin
    # Check if the gem is available
    # 'gem' returns 'true' if it loaded it, false if already loaded,
    # and raises a Gem::LoadError exception on failure.
    # Skip downloading/installing it if it's already here.
    gem(dep.name, dep.requirement)

    # If we get here, we have the gem.
    puts "Gem found matching: #{dep}"
  rescue Gem::LoadError => e
    # Not installed, continue.
    message = e.to_s

    # Sometimes we failed to load because gembag installs too
    # many things. Like 'shoulda' fails to load because two
    # conflicting versions of 'mocha' were installed.
    # Fundamentally, gembag should build a dependency graph and
    case message
      when /Unable to activate/
        puts "Gem found, but funky: #{dep} (#{e})"
      else
        puts "Gem not found: #{dep} (#{e})"
        install_gem(dep.name, dep.requirement, target)
    end # case message
  end # begin / rescue Gem::LoadError
end # deps.each
      else
        puts "Unexpected error: #{e}"
        exit 1
    end # case message
  end # begin / rescue Gem::LoadError
end # deps.each




<MSG> - only install if it's "Could not find"
- abort on any other error

<DFF> @@ -60,9 +60,12 @@ deps.each do |dep|
     case message
       when /Unable to activate/
         puts "Gem found, but funky: #{dep} (#{e})"
-      else
-        puts "Gem not found: #{dep} (#{e})"
+      when /Could not find/
+        puts "Gem not found: #{dep}"
         install_gem(dep.name, dep.requirement, target)
+      else
+        puts "Unexpected error: #{e}"
+        exit 1
     end # case message
   end # begin / rescue Gem::LoadError
 end # deps.each

- only install if it's "Could not find" - abort on any other error