cask: add the choices option to pkg stanza

installer command accepts -applyChoiceChangesXML option to change
customize options on the GUI installer from the commandline.
(`man installer` for more detailed information)

The introduced option `choice` enables the choice changes to be supplied
via pkg stanza without tricks in preflight code.

Library/Homebrew/cask/lib/hbc/artifact/pkg.rb

@@ -2,6 +2,8 @@ require "hbc/artifact/base"
 
 require "hbc/utils/hash_validator"
 
+require "vendor/plist/plist"
+
 module Hbc
   module Artifact
     class Pkg < Base
@@ -16,7 +18,7 @@ module Hbc
         @pkg_install_opts = pkg_description.shift
         begin
           if @pkg_install_opts.respond_to?(:keys)
-            @pkg_install_opts.extend(HashValidator).assert_valid_keys(:allow_untrusted)
+            @pkg_install_opts.extend(HashValidator).assert_valid_keys(:allow_untrusted, :choices)
           elsif @pkg_install_opts
             raise
           end
@@ -52,8 +54,21 @@ module Hbc
         ]
         args << "-verboseR" if Hbc.verbose
         args << "-allowUntrusted" if pkg_install_opts :allow_untrusted
+        if pkg_install_opts :choices
+          args << "-applyChoiceChangesXML"
+          args << choices_xml
+        end
         @command.run!("/usr/sbin/installer", sudo: true, args: args, print_stdout: true)
       end
+
+      def choices_xml
+        path = @cask.staged_path.join("Choices.xml")
+        unless File.exist? path
+          choices = pkg_install_opts :choices
+          IO.write path, Plist::Emit.dump(choices)
+        end
+        path
+      end
     end
   end
 end

Library/Homebrew/cask/test/cask/artifact/pkg_test.rb

@@ -30,4 +30,41 @@ describe Hbc::Artifact::Pkg do
       end
     end
   end
+
+  describe "choices" do
+    before do
+      @cask = Hbc.load("with-choices")
+      shutup do
+        TestHelper.install_without_artifacts(@cask)
+      end
+    end
+
+    it "passes the choice changes xml to the system installer" do
+      pkg = Hbc::Artifact::Pkg.new(@cask,
+                                   command: Hbc::FakeSystemCommand)
+
+      Hbc::FakeSystemCommand.expects_command(["/usr/bin/sudo", "-E", "--", "/usr/sbin/installer", "-pkg", @cask.staged_path.join("MyFancyPkg", "Fancy.pkg"), "-target", "/", "-applyChoiceChangesXML", @cask.staged_path.join("Choices.xml")])
+
+      shutup do
+        pkg.install_phase
+      end
+
+      IO.read(@cask.staged_path.join("Choices.xml")).must_equal <<-EOS.undent
+        <?xml version="1.0" encoding="UTF-8"?>
+        <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+        <plist version="1.0">
+        <array>
+        	<dict>
+        		<key>attributeSetting</key>
+        		<integer>1</integer>
+        		<key>choiceAttribute</key>
+        		<string>selected</string>
+        		<key>choiceIdentifier</key>
+        		<string>choice1</string>
+        	</dict>
+        </array>
+        </plist>
+      EOS
+    end
+  end
 end

Library/Homebrew/cask/test/support/Casks/with-choices.rb

+test_cask 'with-choices' do
+  version '1.2.3'
+  sha256 '8c62a2b791cf5f0da6066a0a4b6e85f62949cd60975da062df44adf887f4370b'
+
+  url "file://#{TEST_FIXTURE_DIR}/cask/MyFancyPkg.zip"
+  homepage 'http://example.com/fancy-pkg'
+
+  pkg 'MyFancyPkg/Fancy.pkg',
+      choices: [
+                 {
+                   'choiceIdentifier' => 'choice1',
+                   'choiceAttribute'  => 'selected',
+                   'attributeSetting' => 1,
+                 },
+               ]
+end