Support multiple chains that start with the same message

- forward ported from rspec-1
- Closes #9.

lib/rspec/mocks/methods.rb

@@ -37,9 +37,14 @@ def unstub(sym)
       def stub_chain(*chain)
         methods = chain.join('.').split('.')
         if methods.length > 1
-          next_in_chain = Object.new
-          stub(methods.shift) { next_in_chain }
-          next_in_chain.stub_chain(*methods)
+          if matching_stub = __mock_proxy.__send__(:find_matching_method_stub, methods[0].to_sym)
+            methods.shift
+            matching_stub.__send__(:invoke, [], nil).stub_chain(*methods)
+          else
+            next_in_chain = Object.new
+            stub(methods.shift) { next_in_chain }
+            next_in_chain.stub_chain(*methods)
+          end
         else
           stub(methods.shift)
         end

spec/rspec/mocks/stub_chain_spec.rb

@@ -34,6 +34,14 @@ module Mocks
         @subject.stub_chain("msg1.msg2.msg3").and_return(:return_value)
         @subject.msg1.msg2.msg3.should equal(:return_value)
       end
+
+      it "returns expected value from two chains with shared messages at the beginning" do
+        @subject.stub_chain(:msg1, :msg2, :msg3, :msg4).and_return(:first)
+        @subject.stub_chain(:msg1, :msg2, :msg3, :msg5).and_return(:second)
+
+        @subject.msg1.msg2.msg3.msg4.should equal(:first)
+        @subject.msg1.msg2.msg3.msg5.should equal(:second)
+      end
     end
   end
 end