Merge pull request #183 from alindeman/hide_const

Add support to temporarily remove constants

features/.nav

@@ -18,9 +18,10 @@
   - explicit.feature
   - general_matchers.feature
   - type_matchers.feature
-- stubbing_constants:
+- mutating_constants:
   - stub_defined_constant.feature
   - stub_undefined_constant.feature
+  - hiding_defined_constant.feature
 - outside_rspec:
   - configuration.feature
   - standalone.feature

features/stubbing_constants/README.md → features/mutating_constants/README.md

@@ -1,4 +1,6 @@
-## Stubbing Constants
+## Mutating Constants
+
+### Stubbing
 
 Support is provided for stubbing constants. Like with method stubs, the
 stubbed constants will be restored to their original state when an
@@ -60,3 +62,21 @@ CardDeck::SUITS # => [:Spades, :Diamonds, :Clubs, :Hearts]
 CardDeck::NUM_CARDS # => raises uninitialized constant error
 ```
 
+### Hiding
+
+Support is also provided for hiding constants. Hiding a constant temporarily
+removes it; it is restored to its original value after the test completes.
+
+```ruby
+FOO = 42
+hide_const("FOO")
+FOO => NameError: uninitialized constant FOO
+```
+
+Like stubbed constants, names must be fully qualified.
+
+Hiding constants that are already undefined has no effect.
+
+```ruby
+hide_const("NO_OP")
+```

features/mutating_constants/hiding_defined_constant.feature

@@ -0,0 +1,64 @@
+Feature: Hide Defined Constant
+
+  Use `hide_const` to remove a constant for the duration of a test.
+
+  Scenario: Hide top-level constant
+    Given a file named "hide_const_spec.rb" with:
+      """ruby
+      FOO = 7
+
+      describe "hiding FOO" do
+        it "can hide FOO" do
+          hide_const("FOO")
+          expect { FOO }.to raise_error(NameError)
+        end
+
+        it "restores the hidden constant when the example completes" do
+          FOO.should eq(7)
+        end
+      end
+      """
+    When I run `rspec hide_const_spec.rb`
+    Then the examples should all pass
+
+  Scenario: Hide nested constant
+    Given a file named "hide_const_spec.rb" with:
+      """ruby
+      module MyGem
+        class SomeClass
+          FOO = 7
+        end
+      end
+
+      module MyGem
+        describe SomeClass do
+          it "hides the nested constant when it is fully qualified" do
+            hide_const("MyGem::SomeClass::FOO")
+            expect { SomeClass::FOO }.to raise_error(NameError)
+          end
+
+          it "restores the hidden constant when the example completes" do
+            MyGem::SomeClass::FOO.should eq(7)
+          end
+        end
+      end
+      """
+    When I run `rspec hide_const_spec.rb`
+    Then the examples should all pass
+
+  Scenario: Hiding undefined constant
+    Given a file named "hide_const_spec.rb" with:
+      """
+      describe "hiding UNDEFINED_CONSTANT" do
+        it "has no effect" do
+          hide_const("UNDEFINED_CONSTANT")
+          expect { UNDEFINED_CONSTANT }.to raise_error(NameError)
+        end
+
+        it "is still undefined after the example completes" do
+          expect { UNDEFINED_CONSTANT }.to raise_error(NameError)
+        end
+      end
+      """
+    When I run `rspec hide_const_spec.rb`
+    Then the examples should all pass

lib/rspec/mocks/example_methods.rb

@@ -79,11 +79,27 @@ def allow_message_expectations_on_nil
       #   CardDeck::SUITS # => our suits array
       #   CardDeck::NUM_CARDS # => uninitialized constant error
       def stub_const(constant_name, value, options = {})
-        ConstantStubber.stub(constant_name, value, options)
+        ConstantMutator.stub(constant_name, value, options)
+      end
+
+      # Hides the named constant with the given value. The constant will be
+      # undefined for the duration of the test.
+      #
+      # Like method stubs, the constant will be restored to its original value
+      # when the example completes.
+      #
+      # @param constant_name [String] The fully qualified name of the constant.
+      #   The current constant scoping at the point of call is not considered.
+      #
+      # @example
+      #
+      #   hide_const("MyClass") # => MyClass is now an undefined constant
+      def hide_const(constant_name)
+        ConstantMutator.hide(constant_name)
       end
 
     private
-      
+
       def declare_double(declared_as, *args)
         args << {} unless Hash === args.last
         args.last[:__declared_as] = declared_as

lib/rspec/mocks/framework.rb

@@ -19,4 +19,4 @@
 require 'rspec/mocks/space'
 require 'rspec/mocks/serialization'
 require 'rspec/mocks/any_instance'
-require 'rspec/mocks/stub_const'
+require 'rspec/mocks/mutate_const'