Remove posix-spawn dependency.

posix-spawn relies on a C extension. This does work under JRuby, but it
won't work on Travis CI as they disallow JRuby C extensions, as they are
considered to not be a good practice.

Instead we are using either Process.spawn on Ruby 1.9, or the
childprocess gem on Ruby 1.8. childprocess uses native JVM APIs on
JRuby, and fork+exec on others.

lib/capybara/poltergeist.rb

@@ -11,6 +11,7 @@ module Capybara
     autoload :Client,          'capybara/poltergeist/client'
     autoload :Util,            'capybara/poltergeist/util'
     autoload :Inspector,       'capybara/poltergeist/inspector'
+    autoload :Spawn,           'capybara/poltergeist/spawn'
 
     require 'capybara/poltergeist/errors'
   end

lib/capybara/poltergeist/client.rb

@@ -1,5 +1,3 @@
-require 'posix/spawn'
-
 module Capybara::Poltergeist
   class Client
     PHANTOMJS_SCRIPT  = File.expand_path('../client/compiled/main.js', __FILE__)
@@ -18,12 +16,14 @@ module Capybara::Poltergeist
       @port      = port
       @inspector = inspector
       @path      = path || PHANTOMJS_NAME
-      at_exit { stop }
+
+      pid = Process.pid
+      at_exit { stop if Process.pid == pid }
     end
 
     def start
       check_phantomjs_version
-      @pid = POSIX::Spawn.spawn(command)
+      @pid = Spawn.spawn(*command)
     end
 
     def stop
@@ -55,7 +55,7 @@ module Capybara::Poltergeist
 
         parts << PHANTOMJS_SCRIPT
         parts << port
-        parts.join(" ")
+        parts
       end
     end
 

lib/capybara/poltergeist/inspector.rb

@@ -1,5 +1,3 @@
-require 'posix/spawn'
-
 module Capybara::Poltergeist
   class Inspector
     BROWSERS = %w(chromium chromium-browser google-chrome safari)
@@ -26,7 +24,7 @@ module Capybara::Poltergeist
 
     def open
       if browser
-        POSIX::Spawn.spawn("#{browser} #{url}")
+        Spawn.spawn(browser, url)
       else
         raise Error, "Could not find a browser executable to open #{url}. " \
                      "You can specify one manually using e.g. `:inspector => 'chromium'` " \

lib/capybara/poltergeist/spawn.rb

@@ -0,0 +1,17 @@
+require 'childprocess'
+
+module Capybara::Poltergeist
+  module Spawn
+    def self.spawn(*args)
+      args = args.map(&:to_s)
+
+      if RUBY_VERSION >= "1.9"
+        Process.spawn(*args)
+      else
+        process = ChildProcess.build(*args)
+        process.start
+        process.pid
+      end
+    end
+  end
+end

poltergeist.gemspec

@@ -16,7 +16,7 @@ Gem::Specification.new do |s|
 
   s.add_dependency "capybara",       "~> 1.0"
   s.add_dependency "json",           "~> 1.6"
-  s.add_dependency "posix-spawn",    "~> 0.3"
+  s.add_dependency "childprocess",   "~> 0.3"
   s.add_dependency "http_parser.rb", "~> 0.5.3"
   s.add_dependency "faye-websocket", "~> 0.4", ">= 0.4.2"
 

spec/unit/inspector_spec.rb

@@ -27,7 +27,7 @@ module Capybara::Poltergeist
 
     it 'can be opened' do
       subject.stub(:port => 1234, :browser => 'chromium')
-      POSIX::Spawn.should_receive(:spawn).with("chromium http://localhost:1234/")
+      Spawn.should_receive(:spawn).with("chromium", "http://localhost:1234/")
       subject.open
     end