Require the 'pp' gem by default, per MRI.

Author: nirvdrum

spec/ruby/core/kernel/pp_spec.rb

@@ -0,0 +1,9 @@
+require_relative '../../spec_helper'
+
+describe "Kernel#pp" do
+  it "lazily loads the 'pp' library and delegates the call to that library" do
+    # Run in child process to ensure 'pp' hasn't been loaded yet.
+    output = ruby_exe("pp [1, 2, 3]")
+    output.should == "[1, 2, 3]\n"
+  end
+end

src/main/ruby/core/kernel.rb

@@ -589,6 +589,11 @@ def printf(*args)
   end
   module_function :printf
 
+  private def pp(*args)
+    require 'pp'
+    pp(*args)
+  end
+
   alias_method :trust, :untaint
   alias_method :untrust, :taint
   alias_method :untrusted?, :tainted?