Deprecate non-opt-in Marshal monkey-patch.

Changelog.md

@@ -5,6 +5,7 @@ Deprecations:
 
 * Deprecate `RSpec::Mocks::TestDouble.extend_onto`. (Myron Marston)
 * Deprecate `RSpec::Mocks::ConstantStubber`. (Jon Rowe)
+* Deprecate `Marshal.dump` monkey-patch without opt-in. (Xavier Shay)
 
 ### 2.99.0.beta2 / 2014-02-17
 [full changelog](http://github.com/rspec/rspec-mocks/compare/v2.99.0.beta1...v2.99.0.beta2)

lib/rspec/mocks/configuration.rb

@@ -6,6 +6,7 @@ class Configuration
       def initialize
         @yield_receiver_to_any_instance_implementation_blocks = false
         @should_warn_about_any_instance_blocks = true
+        @marshal_patched = false
       end
 
       def yield_receiver_to_any_instance_implementation_blocks?
@@ -62,6 +63,14 @@ def syntax
         syntaxes << :expect if Syntax.expect_enabled?
         syntaxes
       end
+
+      def patch_marshal_to_support_partial_doubles=(val)
+        @marshal_patched = val
+      end
+
+      def marshal_patched?
+        @marshal_patched
+      end
     end
 
     def self.configuration

lib/rspec/mocks/extensions/marshal.rb

@@ -6,6 +6,21 @@ def dump_with_mocks(object, *rest)
       if ::RSpec::Mocks.space.nil? || !::RSpec::Mocks.space.registered?(object) || NilClass === object
         dump_without_mocks(object, *rest)
       else
+        unless ::RSpec::Mocks.configuration.marshal_patched?
+          RSpec.warn_deprecation(<<-EOS.gsub(/^\s+\|/, ''))
+            |Using Marshal.dump on stubbed objects relies on a monkey-patch
+            |that is being made opt-in in RSpec 3. To silence this warning
+            |please explicitly enable it:
+            |
+            |RSpec.configure do |rspec|
+            |  rspec.mock_with :rspec do |mocks|
+            |    mocks.patch_marshal_to_support_partial_doubles = true
+            |  end
+            |end
+            |
+            |Called from #{RSpec::CallerFilter.first_non_rspec_line}."
+          EOS
+        end
         dump_without_mocks(object.dup, *rest)
       end
     end

spec/rspec/mocks/extensions/marshal_spec.rb

@@ -31,13 +31,21 @@ def without_space
     end
 
     context 'when rspec-mocks has been fully initialized' do
+      include_context 'with isolated configuration'
+
       it 'duplicates objects with stubbed or mocked implementations before serialization' do
+        RSpec::Mocks.configuration.patch_marshal_to_support_partial_doubles = true
         obj = double(:foo => "bar")
 
         serialized = Marshal.dump(obj)
         expect(Marshal.load(serialized)).to be_an(obj.class)
       end
 
+      it 'provides a deprecation warning' do
+        expect_warn_deprecation_with_call_site('marshal_spec.rb', __LINE__ + 1)
+        Marshal.dump double(:foo => "bar")
+      end
+
       it 'does not duplicate other objects before serialization' do
         obj = UndupableObject.new
 

spec/rspec/mocks/serialization_spec.rb

@@ -3,6 +3,7 @@
 module RSpec
   module Mocks
     describe "Serialization of mocked objects" do
+      include_context 'with isolated configuration'
 
       class SerializableObject < Struct.new(:foo, :bar); end
 
@@ -82,6 +83,7 @@ def set_stub
       end
 
       it 'marshals the same with and without stubbing' do
+        RSpec::Mocks.configuration.patch_marshal_to_support_partial_doubles = true
         expect { set_stub }.to_not change { Marshal.dump(serializable_object) }
       end
     end