Log a warning when methods are reset on a frozen object

Changelog.md

@@ -10,6 +10,9 @@ Breaking Changes for 3.0.0:
 
 Bug Fixes:
 
+* Instead of crashing when cleaning up stub methods on a frozen object, it now
+  issues a warning explaining that it's impossible to clean up the stubs. 
+  (Justin Coyne)
 * Fix regression in 3.0.0.beta1 that caused `double("string_name" => :value)`
   to stop working. (Xavier Shay)
 * Fix the way rspec-mocks and rspec-core interact so that if users

lib/rspec/mocks/method_double.rb

@@ -16,6 +16,7 @@ def initialize(object, method_name, proxy)
         @method_is_proxied = false
         @expectations = []
         @stubs = []
+        @show_frozen_warnings = []
       end
 
       def original_method
@@ -85,6 +86,15 @@ def restore_original_method
         restore_original_visibility
 
         @method_is_proxied = false
+      rescue RuntimeError => e
+        frozen = object_singleton_class.frozen?
+        if frozen && !@show_frozen_warnings.include?(@method_name)
+          RSpec.warn_with "Unable to remove stub method #{@method_name} because the object was frozen.",
+            :call_site => nil
+          @show_frozen_warnings << @method_name
+        elsif !frozen
+          raise e
+        end
       end
 
       # @private

spec/rspec/mocks/matchers/receive_spec.rb

@@ -216,6 +216,17 @@ def receiver.method_missing(*a); end # a poor man's stub...
           target.to receive(:foo).and_return(:baz)
           expect { reset object }.to change { object.foo }.from(:baz).to(:bar)
         end
+
+        context "on a frozen object" do
+          it "removes the method double" do
+            with_isolated_stderr do
+              target.to receive(:foo).and_return(:baz)
+              expect_warning_without_call_site(/Unable to remove stub method foo because the object was frozen./)
+              object.freeze
+              reset object
+            end
+          end
+        end
       end
 
       shared_examples_for "resets partial mocks of any instance cleanly" do