Get rid of the code poking around RSpec internals

Our previous code was prone to out-of-sync worlds:

    with_isolated_config do
      RSpec::Core::ExampleGroup.describe('a view') { it { } }
      RSpec.configuration.world.example_groups # => []
    end

Author: pirj

spec/rspec/rails/example/controller_example_group_spec.rb

@@ -31,18 +31,16 @@ def group_for(klass)
         # before #738 implicit subject definition for controllers caused
         # external methods to take precedence over our let definitions
 
-        with_isolated_config do |config|
-          mod = Module.new do
-            def my_helper
-              "other_value"
-            end
+        mod = Module.new do
+          def my_helper
+            "other_value"
           end
-          config.include mod
-          group.class_exec do
-            let(:my_helper) { "my_value" }
-          end
-          expect(group.new.my_helper).to eq "my_value"
         end
+        config.include mod
+        group.class_exec do
+          let(:my_helper) { "my_value" }
+        end
+        expect(group.new.my_helper).to eq "my_value"
       end
     end
 
@@ -109,10 +107,8 @@ def my_helper
 
       context "when infer_base_class_for_anonymous_controllers is true" do
         around(:example) do |ex|
-          with_isolated_config do |config|
-            config.infer_base_class_for_anonymous_controllers = true
-            ex.run
-          end
+          RSpec.configuration.infer_base_class_for_anonymous_controllers = true
+          ex.run
         end
 
         it "infers the anonymous controller class" do
@@ -129,10 +125,8 @@ def my_helper
 
       context "when infer_base_class_for_anonymous_controllers is false" do
         around(:example) do |ex|
-          with_isolated_config do |config|
-            config.infer_base_class_for_anonymous_controllers = false
-            ex.run
-          end
+          RSpec.configuration.infer_base_class_for_anonymous_controllers = false
+          ex.run
         end
 
         it "sets the anonymous controller class to ApplicationController" do

spec/rspec/rails/example/view_example_group_spec.rb

@@ -249,21 +249,19 @@ def _view; end # Stub method
 
       # Regression test from rspec/rspec-rails#833
       it 'is accessible to configuration-level hooks', pending: pending_only_on_ruby_22_rails_52 do
-        with_isolated_config do
-          run_count = 0
-          RSpec.configuration.before(:each, type: :view) do
-            # `view` is provided from the view example type, and serves to
-            # demonstrate this hook is run in the correct context.
-            allow(view).to receive(:render) { :value }
-            run_count += 1
-          end
-          group = RSpec::Core::ExampleGroup.describe 'a view', type: :view do
-            specify { expect(view.render).to eq(:value) }
-          end
-          group.run(failure_reporter)
-          expect(failure_reporter.exceptions).to eq []
-          expect(run_count).to eq 1
+        run_count = 0
+        RSpec.configuration.before(:each, type: :view) do
+          # `view` is provided from the view example type, and serves to
+          # demonstrate this hook is run in the correct context.
+          allow(view).to receive(:render) { :value }
+          run_count += 1
+        end
+        group = RSpec::Core::ExampleGroup.describe 'a view', type: :view do
+          specify { expect(view.render).to eq(:value) }
         end
+        group.run(failure_reporter)
+        expect(failure_reporter.exceptions).to eq []
+        expect(run_count).to eq 1
       end
     end
 

spec/spec_helper.rb

@@ -15,6 +15,7 @@ class Application < ::Rails::Application
 I18n.enforce_available_locales = true
 
 require 'rspec/support/spec'
+require 'rspec/core/sandbox'
 require 'rspec/rails'
 require 'ammeter/init'
 
@@ -51,10 +52,18 @@ def self.run_all(reporter = nil)
   config.warnings = true
   config.raise_on_warning = true
 
+  # Execute a provided block with RSpec global objects (configuration,
+  # world, current example) reset. This is used to test specs with RSpec.
   config.around(:example) do |example|
-    real_world = RSpec.world
-    RSpec.instance_variable_set(:@world, RSpec::Core::World.new)
-    example.run
-    RSpec.instance_variable_set(:@world, real_world)
+    RSpec::Core::Sandbox.sandboxed do |sandbox_config|
+      # If there is an example-within-an-example, we want to make sure the inner
+      # example does not get a reference to the outer example (the real spec) if
+      # it calls something like `pending`.
+      sandbox_config.before(:context) { RSpec.current_example = nil }
+      RSpec::Rails.initialize_configuration(sandbox_config)
+      example.run
+    end
   end
+
+  config.include RSpec::Rails::FeatureCheck
 end

spec/support/helpers.rb

@@ -27,10 +27,6 @@ def define_group_in(path, group_definition)
     end
   end
 
-  around(:example) do |ex|
-    with_isolated_config(&ex)
-  end
-
   it "adds does not add `:type` metadata on inclusion" do
     mixin = self.mixin
     group = RSpec.describe { include mixin }