Add currently_executing_a_context_hook? to ExampleGroup

This is useful because at the moment the only way to determine if an
example is currently executing a context hook is to look at it's inspect
string. Here, we add a simple boolean flag which is triggered in before
and after context hook execution.

This is needed by rspec/rspec-rails#1501.

lib/rspec/core/example_group.rb

@@ -414,6 +414,8 @@ def self.set_it_up(description, *args, &example_group_block)
         )
         ExampleGroups.assign_const(self)
 
+        @currently_executing_a_context_hook = false
+
         hooks.register_globals(self, RSpec.configuration.hooks)
         RSpec.configuration.configure_group(self)
       end
@@ -486,15 +488,24 @@ def self.store_before_context_ivars(example_group_instance)
         end
       end
 
+      # Returns true if a `before(:context)` or `after(:context)`
+      # hook is currently executing.
+      def self.currently_executing_a_context_hook?
+        @currently_executing_a_context_hook
+      end
+
       # @private
       def self.run_before_context_hooks(example_group_instance)
         set_ivars(example_group_instance, superclass_before_context_ivars)
 
+        @currently_executing_a_context_hook = true
+
         ContextHookMemoized::Before.isolate_for_context_hook(example_group_instance) do
           hooks.run(:before, :context, example_group_instance)
         end
       ensure
         store_before_context_ivars(example_group_instance)
+        @currently_executing_a_context_hook = false
       end
 
       if RUBY_VERSION.to_f >= 1.9
@@ -525,11 +536,14 @@ def self.superclass_before_context_ivars
       def self.run_after_context_hooks(example_group_instance)
         set_ivars(example_group_instance, before_context_ivars)
 
+        @currently_executing_a_context_hook = true
+
         ContextHookMemoized::After.isolate_for_context_hook(example_group_instance) do
           hooks.run(:after, :context, example_group_instance)
         end
       ensure
         before_context_ivars.clear
+        @currently_executing_a_context_hook = false
       end
 
       # Runs all the examples in this group.

spec/rspec/core/example_group_spec.rb

@@ -713,6 +713,51 @@ def define_and_run_group(define_outer_example = false)
           group.run
           expect(order).to eq([:example, :after_example, :example, :after_example])
         end
+
+        describe "#currently_executing_a_context_hook?" do
+          it "sets currently_executing_a_context_hook? to false initially" do
+            group = RSpec.describe
+            expect(group.currently_executing_a_context_hook?).to be false
+          end
+
+          it "sets currently_executing_a_context_hook? during before(:context) execution" do
+            group = RSpec.describe
+            hook_result = nil
+            group.before(:context) { hook_result = group.currently_executing_a_context_hook? }
+            group.example("") {}
+            group.run
+            expect(hook_result).to be true
+          end
+
+          it "does not set currently_executing_a_context_hook? outside of before(:context) execution" do
+            group = RSpec.describe
+            hook_result = nil
+
+            group.before(:context) { hook_result = group.currently_executing_a_context_hook? }
+            group.before(:each) { hook_result = group.currently_executing_a_context_hook? }
+            group.example("") {}
+            group.run
+            expect(hook_result).to be false
+          end
+
+          it "sets currently_executing_a_context_hook? during after(:context) execution" do
+            group = RSpec.describe
+            hook_result = nil
+
+            group.after(:context) { hook_result = group.currently_executing_a_context_hook? }
+            group.example("") {}
+            group.run
+            expect(hook_result).to be true
+          end
+
+          it "unsets currently_executing_a_context_hook? after an after(:context) hook is done" do
+            group = RSpec.describe
+            group.after(:context) { }
+            group.example("") {}
+            group.run
+            expect(group.currently_executing_a_context_hook?).to be false
+          end
+        end
       end
 
       it "runs the before alls in order" do