Fixes #20799

When `#perform_later` is called the locale isn't stored on the
queue, which results in a locale reset when the job is performed.

An example of the problem:

    I18n.locale = 'de'
    HelloJob.perform_now # german message, correct

but

    I18n.locale = 'de'
    HelloJob.perform_later # english message, incorrect

This PR attaches the current I18n.locale to every job during the
serialization process. It is then restored during deserialization
and used to perform the job with the correct locale.

It falls back to the default locale if no serialized locale is
found in order to provide backward compatibility with previously
stored jobs. It is not necessary to clear the queue for the update.

activejob/CHANGELOG.md

+*   Include I18n.locale into job serialization/deserialization and use it around
+    `perform`.
+
+    Fixes #20799.
+
+    *Johannes Opper*
+
 *   Allow `DelayedJob`, `Sidekiq`, `qu`, and `que` to report the job id back to
     `ActiveJob::Base` as `provider_job_id`.
 

activejob/lib/active_job/base.rb

@@ -5,6 +5,7 @@
 require 'active_job/execution'
 require 'active_job/callbacks'
 require 'active_job/logging'
+require 'active_job/translation'
 
 module ActiveJob #:nodoc:
   # = Active Job
@@ -60,6 +61,7 @@ class Base
     include Execution
     include Callbacks
     include Logging
+    include Translation
 
     ActiveSupport.run_load_hooks(:active_job, self)
   end

activejob/lib/active_job/core.rb

@@ -20,6 +20,9 @@ module Core
 
       # ID optionally provided by adapter
       attr_accessor :provider_job_id
+
+      # I18n.locale to be used during the job.
+      attr_accessor :locale
     end
 
     # These methods will be included into any Active Job object, adding
@@ -68,7 +71,8 @@ def serialize
         'job_class'  => self.class.name,
         'job_id'     => job_id,
         'queue_name' => queue_name,
-        'arguments'  => serialize_arguments(arguments)
+        'arguments'  => serialize_arguments(arguments),
+        'locale'     => I18n.locale
       }
     end
 
@@ -96,6 +100,7 @@ def deserialize(job_data)
       self.job_id               = job_data['job_id']
       self.queue_name           = job_data['queue_name']
       self.serialized_arguments = job_data['arguments']
+      self.locale               = job_data['locale'] || I18n.locale
     end
 
     private

activejob/lib/active_job/translation.rb

+module ActiveJob
+  module Translation #:nodoc:
+    extend ActiveSupport::Concern
+
+    included do
+      around_perform do |job, block, _|
+        I18n.with_locale(job.locale, &block)
+      end
+    end
+  end
+end

activejob/test/cases/job_serialization_test.rb

@@ -12,4 +12,20 @@ class JobSerializationTest < ActiveSupport::TestCase
     GidJob.perform_later @person
     assert_equal "Person with ID: 5", JobBuffer.last_value
   end
+
+  test 'serialize includes current locale' do
+    assert_equal :en, HelloJob.new.serialize['locale']
+  end
+
+  test 'deserialize sets locale' do
+    job = HelloJob.new
+    job.deserialize 'locale' => :es
+    assert_equal :es, job.locale
+  end
+
+  test 'deserialize sets default locale' do
+    job = HelloJob.new
+    job.deserialize({})
+    assert_equal :en, job.locale
+  end
 end

activejob/test/cases/translation_test.rb

+require 'helper'
+require 'jobs/translated_hello_job'
+
+class TranslationTest < ActiveSupport::TestCase
+  setup do
+    JobBuffer.clear
+    I18n.available_locales = [:en, :de]
+    @job = TranslatedHelloJob.new('Johannes')
+  end
+
+  teardown do
+    I18n.available_locales = [:en]
+  end
+
+  test 'it performs the job in the given locale' do
+    @job.locale = :de
+    @job.perform_now
+    assert_equal "Johannes says Guten Tag", JobBuffer.last_value
+  end
+end

activejob/test/integration/queuing_test.rb

@@ -68,4 +68,21 @@ class QueuingTest < ActiveSupport::TestCase
     refute delayed_test_job.provider_job_id.nil?,
       'Provider job id should by set for delayed jobs by provider'
   end
+
+  test 'current locale is kept while running perform_later' do
+    skip if adapter_is?(:inline)
+
+    begin
+      I18n.available_locales = [:en, :de]
+      I18n.locale = :de
+
+      TestJob.perform_later @id
+      wait_for_jobs_to_finish_for(5.seconds)
+      assert job_executed
+      assert_equal 'de', job_output
+    ensure
+      I18n.available_locales = [:en]
+      I18n.locale = :en
+    end
+  end
 end

activejob/test/jobs/translated_hello_job.rb

+require_relative '../support/job_buffer'
+
+class TranslatedHelloJob < ActiveJob::Base
+  def perform(greeter = "David")
+    translations = { en: 'Hello', de: 'Guten Tag' }
+    hello        = translations[I18n.locale]
+
+    JobBuffer.add("#{greeter} says #{hello}")
+  end
+end

activejob/test/support/integration/dummy_app_template.rb

@@ -8,13 +8,17 @@
 JobsManager.current_manager.setup
 CODE
 
+initializer 'i18n.rb', <<-CODE
+I18n.available_locales = [:en, :de]
+CODE
+
 file 'app/jobs/test_job.rb', <<-CODE
 class TestJob < ActiveJob::Base
   queue_as :integration_tests
 
   def perform(x)
     File.open(Rails.root.join("tmp/\#{x}"), "w+") do |f|
-      f.write x
+      f.write I18n.locale
     end
   end
 end

activejob/test/support/integration/test_case_helpers.rb

@@ -45,4 +45,8 @@ def wait_for_jobs_to_finish_for(seconds=60)
     def job_executed
       Dummy::Application.root.join("tmp/#{@id}").exist?
     end
+
+    def job_output
+      File.read Dummy::Application.root.join("tmp/#{@id}")
+    end
 end

guides/source/active_job_basics.md

@@ -280,6 +280,19 @@ UserMailer.welcome(@user).deliver_later
 ```
 
 
+Internationalization
+--------------------
+
+Each job uses the `I18n.locale` set when the job was created. Useful if you send
+emails asynchronously:
+
+```ruby
+I18n.locale = :eo
+
+UserMailer.welcome(@user).deliver_later # Email will be localized to Esparanto.
+```
+
+
 GlobalID
 --------