Fix transfer_nested_constants option of stub_const.

My changes in deec990 caused it to blow up in the face of inherited constants.

Changelog.md

@@ -1,3 +1,11 @@
+### dev
+[full changelog](http://github.com/rspec/rspec-mocks/compare/v2.11.2...master)
+
+Bug fixes
+
+* Fix `:transfer_nested_constants` option of `stub_const` so that it
+  doesn't blow up when there are inherited constants. (Myron Marston)
+
 ### 2.11.2 / 2012-08-11
 [full changelog](http://github.com/rspec/rspec-mocks/compare/v2.11.1...v2.11.2)
 

lib/rspec/mocks/stub_const.rb

@@ -10,17 +10,22 @@ module RecursiveConstMethods
       # we need to conditionally define methods to ignore the top-level/inherited
       # constants.
       #
-      # Given `class A; end`:
+      # Given:
+      #   class A; B = 1; end
+      #   class C < A; end
       #
       # On 1.8:
-      #   - A.const_get("Hash") # => ::Hash
-      #   - A.const_defined?("Hash") # => false
-      #   - Neither method accepts the extra `inherit` argument
+      #   - C.const_get("Hash") # => ::Hash
+      #   - C.const_defined?("Hash") # => false
+      #   - C.constants # => ["A"]
+      #   - None of these methods accept the extra `inherit` argument
       # On 1.9:
-      #   - A.const_get("Hash") # => ::Hash
-      #   - A.const_defined?("Hash") # => true
-      #   - A.const_get("Hash", false) # => raises NameError
-      #   - A.const_defined?("Hash", false) # => false
+      #   - C.const_get("Hash") # => ::Hash
+      #   - C.const_defined?("Hash") # => true
+      #   - C.const_get("Hash", false) # => raises NameError
+      #   - C.const_defined?("Hash", false) # => false
+      #   - C.constants # => [:A]
+      #   - C.constants(false) #=> []
       if Module.method(:const_defined?).arity == 1
         def const_defined_on?(mod, const_name)
           mod.const_defined?(const_name)
@@ -33,6 +38,10 @@ def get_const_defined_on(mod, const_name)
 
           raise NameError, "uninitialized constant #{mod.name}::#{const_name}"
         end
+
+        def constants_defined_on(mod)
+          mod.constants.select { |c| const_defined_on?(mod, c) }
+        end
       else
         def const_defined_on?(mod, const_name)
           mod.const_defined?(const_name, false)
@@ -41,6 +50,10 @@ def const_defined_on?(mod, const_name)
         def get_const_defined_on(mod, const_name)
           mod.const_get(const_name, false)
         end
+
+        def constants_defined_on(mod)
+          mod.constants(false)
+        end
       end
 
       def recursive_const_get(const_name)
@@ -217,10 +230,10 @@ def verify_constants_to_transfer!
 
           if @transfer_nested_constants.is_a?(Array)
             @transfer_nested_constants = @transfer_nested_constants.map(&:to_s) if RUBY_VERSION == '1.8.7'
-            undefined_constants = @transfer_nested_constants - @original_value.constants
+            undefined_constants = @transfer_nested_constants - constants_defined_on(@original_value)
 
             if undefined_constants.any?
-              available_constants = @original_value.constants - @transfer_nested_constants
+              available_constants = constants_defined_on(@original_value) - @transfer_nested_constants
               raise ArgumentError,
                 "Cannot transfer nested constant(s) #{undefined_constants.join(' and ')} " +
                 "for #{@full_constant_name} since they are not defined. Did you mean " +
@@ -229,7 +242,7 @@ def verify_constants_to_transfer!
 
             @transfer_nested_constants
           else
-            @original_value.constants
+            constants_defined_on(@original_value)
           end
         end
       end

spec/rspec/mocks/stub_const_spec.rb

@@ -12,6 +12,10 @@ class NestedEvenMore
   end
 end
 
+class TestSubClass < TestClass
+  P = :p
+end
+
 module RSpec
   module Mocks
     describe "Constant Stubbing" do
@@ -121,6 +125,24 @@ def change_const_value_to(value)
             stub::Nested.should be(tc_nested)
           end
 
+          it 'does not transfer nested constants that are inherited from a superclass' do
+            stub = Module.new
+            stub_const("TestSubClass", stub, :transfer_nested_constants => true)
+            stub::P.should eq(:p)
+            defined?(stub::M).should be_false
+            defined?(stub::N).should be_false
+          end
+
+          it 'raises an error when asked to transfer a nested inherited constant' do
+            original_tsc = TestSubClass
+
+            expect {
+              stub_const("TestSubClass", Module.new, :transfer_nested_constants => [:M])
+            }.to raise_error(ArgumentError)
+
+            TestSubClass.should be(original_tsc)
+          end
+
           it 'allows nested constants to be selectively transferred to a stub module' do
             stub = Module.new
             stub_const("TestClass", stub, :transfer_nested_constants => [:M, :N])