ActiveSupport::CurrentAttributes provides a thread-isolated attributes singleton (#29180)

* Add ActiveSupport::CurrentAttributes to provide a thread-isolated attributes singleton

* Need to require first

* Move stubs into test namespace.

Thus they won't conflict with other Current and Person stubs.

* End of the line for you, whitespace!

* Support super in attribute methods.

Define instance level accessors in an included module such that
`super` in an overriden accessor works, akin to Active Model.

* Spare users the manual require.

Follow the example of concerns, autoload in the top level Active Support file.

* Add bidelegation support

* Rename #expose to #set. Simpler, clearer

* Automatically reset every instance.

Skips the need for users to actively embed something that resets
their CurrentAttributes instances.

* Fix test name; add tangible name value when blank.

* Try to ensure we run after a request as well.

* Delegate all missing methods to the instance

This allows regular `delegate` to serve, so we don't need bidelegate.

* Properly test resetting after execution cycle.

Also remove the stale puts debugging.

* Update documentation to match new autoreset

1 files changed, 88 insertions, 0 deletions

diff --git a/railties/test/application/current_attributes_integration_test.rb b/railties/test/application/current_attributes_integration_test.rb
new file mode 100644
index 0000000000..eea2a791a2
--- /dev/null
+++ b/railties/test/application/current_attributes_integration_test.rb
@@ -0,0 +1,88 @@
+require "isolation/abstract_unit"
+require "rack/test"
+
+class CurrentAttributesIntegrationTest < ActiveSupport::TestCase
+  include ActiveSupport::Testing::Isolation
+  include Rack::Test::Methods
+
+  setup do
+    build_app
+
+    app_file "app/services/current.rb", <<-RUBY
+      class Current < ActiveSupport::CurrentAttributes
+        attribute :customer
+
+        resets { Time.zone = "UTC" }
+
+        def customer=(customer)
+          super
+          Time.zone = customer.try(:time_zone)
+        end
+      end
+    RUBY
+
+    app_file "app/models/customer.rb", <<-RUBY
+      class Customer < Struct.new(:name)
+        def time_zone
+          "Copenhagen"
+        end
+      end
+    RUBY
+
+    app_file "config/routes.rb", <<-RUBY
+      Rails.application.routes.draw do
+        get "/customers/:action", controller: :customers
+      end
+    RUBY
+
+    app_file "app/controllers/customers_controller.rb", <<-RUBY
+      class CustomersController < ApplicationController
+        def set_current_customer
+          Current.customer = Customer.new("david")
+          render :index
+        end
+
+        def set_no_customer
+          render :index
+        end
+      end
+    RUBY
+
+    app_file "app/views/customers/index.html.erb", <<-RUBY
+      <%= Current.customer.try(:name) || 'noone' %>,<%= Time.zone.name %>
+    RUBY
+
+    app_file "app/executor_intercept.rb", <<-RUBY
+      check_state = -> { puts [ Current.customer.try(:name) || "noone", Time.zone.name ].join(",") }
+
+      check_state.call
+
+      Rails.application.executor.wrap do
+        Current.customer = Customer.new("david")
+        check_state.call
+      end
+
+      check_state.call
+    RUBY
+
+    require "#{app_path}/config/environment"
+  end
+
+  teardown :teardown_app
+
+  test "current customer is assigned and cleared" do
+    get "/customers/set_current_customer"
+    assert_equal 200, last_response.status
+    assert_match(/david,Copenhagen/, last_response.body)
+
+    get "/customers/set_no_customer"
+    assert_equal 200, last_response.status
+    assert_match(/noone,UTC/, last_response.body)
+  end
+
+  test "resets after execution" do
+    Dir.chdir(app_path) do
+      assert_equal "noone,UTC\ndavid,Copenhagen\nnoone,UTC\n", `bin/rails runner app/executor_intercept.rb`
+    end
+  end
+end