Support jruby external dependencies.

* Add tests that run only if 'jruby' is installed.
* Note that if your formula has :jruby deps, it should likely
  "depend_on 'jruby'" as well.

Library/Homebrew/formula.rb

@@ -475,7 +475,7 @@ private
 
     def depends_on name
       @deps ||= []
-      @external_deps ||= {:python => [], :ruby => [], :perl => []}
+      @external_deps ||= {:python => [], :perl => [], :ruby => [], :jruby => []}
 
       case name
       when String
@@ -483,7 +483,7 @@ private
       when Hash
         key, value = name.shift
         case value
-        when :python, :ruby, :perl
+        when :python, :perl, :ruby, :jruby
           @external_deps[value] << key
           return
         when :optional, :recommended

Library/Homebrew/formula_installer.rb

@@ -43,6 +43,13 @@ Homebrew does not provide formulae for Ruby dependencies, rubygems does:
     gem install #{dep}
     EOS
   end
+  def jrberr dep; <<-EOS
+Unsatisfied dependency "#{dep}"
+Homebrew does not provide formulae for JRuby dependencies, rubygems does:
+
+    jruby -S gem install #{dep}
+    EOS
+  end
 
   def check_external_deps f
     return unless f.external_deps
@@ -56,6 +63,9 @@ Homebrew does not provide formulae for Ruby dependencies, rubygems does:
     f.external_deps[:ruby].each do |dep|
       raise rberr(dep) unless quiet_system "/usr/bin/env", "ruby", "-rubygems", "-e", "require '#{dep}'"
     end
+    f.external_deps[:jruby].each do |dep|
+      raise rberr(dep) unless quiet_system "/usr/bin/env", "jruby", "-rubygems", "-e", "require '#{dep}'"
+    end
   end
 
   def check_formula_deps f

Library/Homebrew/test/test_external_deps.rb

@@ -27,6 +27,10 @@ class DontActuallyInstall < FormulaInstaller
   def rberr dep
     "Ruby module install message."
   end
+
+  def jrberr dep
+    "JRuby module install message."
+  end
 end
 
 
@@ -79,6 +83,22 @@ class GoodRubyBall <TestBall
   end
 end
 
+class BadJRubyBall <TestBall
+  depends_on "notapackage" => :jruby
+
+  def initialize name=nil
+    super "uses_jruby_ball"
+  end
+end
+
+class GoodJRubyBall <TestBall
+  depends_on "date" => :jruby
+
+  def initialize name=nil
+    super "uses_jruby_ball"
+  end
+end
+
 
 class ExternalDepsTests < Test::Unit::TestCase
   def check_deps_fail f
@@ -117,4 +137,13 @@ class ExternalDepsTests < Test::Unit::TestCase
   def test_good_ruby_deps
     check_deps_pass GoodRubyBall
   end
+
+  # Only run these next two tests if jruby is installed.
+  def test_bad_jruby_deps
+    check_deps_fail BadJRubyBall unless `/usr/bin/which jruby`.chomp.empty?
+  end
+
+  def test_good_jruby_deps
+    check_deps_pass GoodJRubyBall unless `/usr/bin/which jruby`.chomp.empty?
+  end
 end