From 748b21db8ff850378b20a69ccd4215c06abea03e Mon Sep 17 00:00:00 2001 From: David Heinemeier Hansson Date: Thu, 17 Dec 2015 14:28:19 +0100 Subject: Add thread_m/cattr_accessor/reader/writer suite of methods for declaring class and module variables that live per-thread --- activesupport/CHANGELOG.md | 49 ++++++++ .../lib/active_support/core_ext/module.rb | 1 + .../module/attribute_accessors_per_thread.rb | 140 +++++++++++++++++++++ .../lib/active_support/per_thread_registry.rb | 3 + .../module/attribute_accessor_per_thread_test.rb | 109 ++++++++++++++++ 5 files changed, 302 insertions(+) create mode 100644 activesupport/lib/active_support/core_ext/module/attribute_accessors_per_thread.rb create mode 100644 activesupport/test/core_ext/module/attribute_accessor_per_thread_test.rb diff --git a/activesupport/CHANGELOG.md b/activesupport/CHANGELOG.md index 07f7fae5d5..386ef821a7 100644 --- a/activesupport/CHANGELOG.md +++ b/activesupport/CHANGELOG.md @@ -1,3 +1,52 @@ +* Add thread_m/cattr_accessor/reader/writer suite of methods for declaring class and module variables that live per-thread. + This makes it easy to declare per-thread globals that are encapsulated. Note: This is a sharp edge. A wild proliferation + of globals is A Bad Thing. But like other sharp tools, when it's right, it's right. + + Here's an example of a simple event tracking system where the object being tracked needs not pass a creator that it + doesn't need itself along: + + module Current + thread_mattr_accessor :account + thread_mattr_accessor :user + + def self.reset() self.account = self.user = nil end + end + + class ApplicationController < ActiveController::Base + before_action :set_current + after_action { Current.reset } + + private + def set_current + Current.account = Account.find(params[:account_id]) + Current.person = Current.account.people.find(params[:person_id]) + end + end + + class MessagesController < ApplicationController + def create + @message = Message.create!(message_params) + end + end + + class Message < ApplicationRecord + has_many :events + after_create :track_created + + private + def track_created + events.create! origin: self, action: :create + end + end + + class Event < ApplicationRecord + belongs_to :creator, class_name: 'Person' + before_validation { self.creator ||= Current.person } + end + + *DHH* + + * Deprecated `Module#qualified_const_` in favour of the builtin Module#const_ methods. diff --git a/activesupport/lib/active_support/core_ext/module.rb b/activesupport/lib/active_support/core_ext/module.rb index b4efff8b24..ef038331c2 100644 --- a/activesupport/lib/active_support/core_ext/module.rb +++ b/activesupport/lib/active_support/core_ext/module.rb @@ -3,6 +3,7 @@ require 'active_support/core_ext/module/introspection' require 'active_support/core_ext/module/anonymous' require 'active_support/core_ext/module/reachable' require 'active_support/core_ext/module/attribute_accessors' +require 'active_support/core_ext/module/attribute_accessors_per_thread' require 'active_support/core_ext/module/attr_internal' require 'active_support/core_ext/module/concerning' require 'active_support/core_ext/module/delegation' diff --git a/activesupport/lib/active_support/core_ext/module/attribute_accessors_per_thread.rb b/activesupport/lib/active_support/core_ext/module/attribute_accessors_per_thread.rb new file mode 100644 index 0000000000..36fe52cea1 --- /dev/null +++ b/activesupport/lib/active_support/core_ext/module/attribute_accessors_per_thread.rb @@ -0,0 +1,140 @@ +require 'active_support/core_ext/array/extract_options' + +# Extends the module object with class/module and instance accessors for +# class/module attributes, just like the native attr* accessors for instance +# attributes, but does so on a per-thread basis. +# +# So the values are scoped within the Thread.current space under the class name +# of the module. +class Module + # Defines a per-thread class attribute and creates class and instance reader methods. + # The underlying per-thread class variable is set to +nil+, if it is not previously defined. + # + # module Current + # thread_mattr_reader :user + # end + # + # Current.user # => nil + # Thread.current[:attr_Current_user] = "DHH" + # Current.user # => "DHH" + # + # The attribute name must be a valid method name in Ruby. + # + # module Foo + # thread_mattr_reader :"1_Badname" + # end + # # => NameError: invalid attribute name: 1_Badname + # + # If you want to opt out the creation on the instance reader method, pass + # instance_reader: false or instance_accessor: false. + # + # class Current + # thread_mattr_reader :user, instance_reader: false + # end + # + # Current.new.user # => NoMethodError + def thread_mattr_reader(*syms) + options = syms.extract_options! + + syms.each do |sym| + raise NameError.new("invalid attribute name: #{sym}") unless sym =~ /^[_A-Za-z]\w*$/ + class_eval(<<-EOS, __FILE__, __LINE__ + 1) + def self.#{sym} + Thread.current[:"attr_#{name}_#{sym}"] + end + EOS + + unless options[:instance_reader] == false || options[:instance_accessor] == false + class_eval(<<-EOS, __FILE__, __LINE__ + 1) + def #{sym} + Thread.current[:"attr_#{self.class.name}_#{sym}"] + end + EOS + end + end + end + alias :thread_cattr_reader :thread_mattr_reader + + # Defines a per-thread class attribute and creates a class and instance writer methods to + # allow assignment to the attribute. + # + # module Current + # thread_mattr_writer :user + # end + # + # Current.user = "DHH" + # Thread.current[:attr_Current_user] # => "DHH" + # + # If you want to opt out the instance writer method, pass + # instance_writer: false or instance_accessor: false. + # + # class Current + # thread_mattr_writer :user, instance_writer: false + # end + # + # Current.new.user = "DHH" # => NoMethodError + def thread_mattr_writer(*syms) + options = syms.extract_options! + syms.each do |sym| + raise NameError.new("invalid attribute name: #{sym}") unless sym =~ /^[_A-Za-z]\w*$/ + class_eval(<<-EOS, __FILE__, __LINE__ + 1) + def self.#{sym}=(obj) + Thread.current[:"attr_#{name}_#{sym}"] = obj + end + EOS + + unless options[:instance_writer] == false || options[:instance_accessor] == false + class_eval(<<-EOS, __FILE__, __LINE__ + 1) + def #{sym}=(obj) + Thread.current[:"attr_#{self.class.name}_#{sym}"] = obj + end + EOS + end + end + end + alias :thread_cattr_writer :thread_mattr_writer + + # Defines both class and instance accessors for class attributes. + # + # class Current + # thread_mattr_accessor :user + # end + # + # Current.user = "DHH" + # Current.user # => "DHH" + # Current.new.user # => "DHH" + # + # If a subclass changes the value then that will not change the value for + # parent class. Similarly if parent class changes the value then that will not + # change the value of subclasses either. + # + # class Customer < Account + # end + # + # Customer.user = "CHH" + # Account.user # => "DHH" + # + # To opt out of the instance writer method, pass instance_writer: false. + # To opt out of the instance reader method, pass instance_reader: false. + # + # class Current + # thread_mattr_accessor :user, instance_writer: false, instance_reader: false + # end + # + # Current.new.user = "DHH" # => NoMethodError + # Current.new.user # => NoMethodError + # + # Or pass instance_accessor: false, to opt out both instance methods. + # + # class Current + # mattr_accessor :user, instance_accessor: false + # end + # + # Current.new.user = "DHH" # => NoMethodError + # Current.new.user # => NoMethodError + def thread_mattr_accessor(*syms, &blk) + thread_mattr_reader(*syms, &blk) + thread_mattr_writer(*syms, &blk) + end + alias :thread_cattr_accessor :thread_mattr_accessor +end diff --git a/activesupport/lib/active_support/per_thread_registry.rb b/activesupport/lib/active_support/per_thread_registry.rb index a909a65bb6..88e2b12cc7 100644 --- a/activesupport/lib/active_support/per_thread_registry.rb +++ b/activesupport/lib/active_support/per_thread_registry.rb @@ -1,6 +1,9 @@ require 'active_support/core_ext/module/delegation' module ActiveSupport + # NOTE: This approach has been deprecated for end-user code in favor of thread_mattr_accessor and friends. + # Please use that approach instead. + # # This module is used to encapsulate access to thread local variables. # # Instead of polluting the thread locals namespace: diff --git a/activesupport/test/core_ext/module/attribute_accessor_per_thread_test.rb b/activesupport/test/core_ext/module/attribute_accessor_per_thread_test.rb new file mode 100644 index 0000000000..b8d6c00ff7 --- /dev/null +++ b/activesupport/test/core_ext/module/attribute_accessor_per_thread_test.rb @@ -0,0 +1,109 @@ +require 'abstract_unit' +require 'active_support/core_ext/module/attribute_accessors_per_thread' + +class ModuleAttributeAccessorTest < ActiveSupport::TestCase + def setup + @class = Class.new do + thread_mattr_accessor :foo + thread_mattr_accessor :bar, instance_writer: false + thread_mattr_reader :shaq, instance_reader: false + thread_mattr_accessor :camp, instance_accessor: false + end + + @object = @class.new + end + + def test_should_use_mattr_default + Thread.new do + assert_nil @class.foo + assert_nil @object.foo + end.join + end + + def test_should_set_mattr_value + Thread.new do + @class.foo = :test + assert_equal :test, @class.foo + + @class.foo = :test2 + assert_equal :test2, @class.foo + end.join + end + + def test_should_not_create_instance_writer + Thread.new do + assert_respond_to @class, :foo + assert_respond_to @class, :foo= + assert_respond_to @object, :bar + assert !@object.respond_to?(:bar=) + end.join + end + + def test_should_not_create_instance_reader + Thread.new do + assert_respond_to @class, :shaq + assert !@object.respond_to?(:shaq) + end.join + end + + def test_should_not_create_instance_accessors + Thread.new do + assert_respond_to @class, :camp + assert !@object.respond_to?(:camp) + assert !@object.respond_to?(:camp=) + end.join + end + + def test_values_should_not_bleed_between_threads + threads = [] + threads << Thread.new do + @class.foo = 'things' + sleep 1 + assert_equal 'things', @class.foo + end + + threads << Thread.new do + @class.foo = 'other things' + sleep 1 + assert_equal 'other things', @class.foo + end + + threads << Thread.new do + @class.foo = 'really other things' + sleep 1 + assert_equal 'really other things', @class.foo + end + + threads.each { |t| t.join } + end + + def test_should_raise_name_error_if_attribute_name_is_invalid + exception = assert_raises NameError do + Class.new do + thread_cattr_reader "1nvalid" + end + end + assert_equal "invalid attribute name: 1nvalid", exception.message + + exception = assert_raises NameError do + Class.new do + thread_cattr_writer "1nvalid" + end + end + assert_equal "invalid attribute name: 1nvalid", exception.message + + exception = assert_raises NameError do + Class.new do + thread_mattr_reader "1valid_part" + end + end + assert_equal "invalid attribute name: 1valid_part", exception.message + + exception = assert_raises NameError do + Class.new do + thread_mattr_writer "2valid_part" + end + end + assert_equal "invalid attribute name: 2valid_part", exception.message + end +end -- cgit v1.2.3