Additionally trigger i18n configuration setup before any eager loading [#6353 state:resolved]

This handles the case where config.cache_classes is true and classes
are loaded before the I18n load path has had a chance to be populated.

Signed-off-by: Santiago Pastorino <santiago@wyeworks.com>

activesupport/lib/active_support/i18n_railtie.rb

@@ -24,9 +24,8 @@ module I18n
       end
     end
 
-    # Set the i18n configuration only after initialization since a lot of
-    # configuration is still usually done in application initializers.
-    config.after_initialize do |app|
+    # Proc to set up i18n configuration
+    init_load_path = Proc.new do |app|
       fallbacks = app.config.i18n.delete(:fallbacks)
 
       app.config.i18n.each do |setting, value|
@@ -46,6 +45,14 @@ module I18n
       reloader.execute_if_updated
     end
 
+    # Set the i18n configuration only after initialization since a lot of
+    # configuration is still usually done in application initializers.
+    config.after_initialize(&init_load_path)
+
+    # Trigger i18n config before any eager loading has happened
+    # so it's ready if any classes require it when eager loaded
+    config.before_eager_load(&init_load_path)
+
   protected
 
     def self.include_fallbacks_module

railties/test/application/initializers/i18n_test.rb

@@ -63,6 +63,36 @@ module ApplicationTests
       assert I18n.load_path.include?("#{app_path}/config/another_locale.yml")
     end
 
+    test "load_path is populated before eager loaded models" do
+      add_to_config <<-RUBY
+        config.cache_classes = true
+      RUBY
+
+      app_file "config/locales/en.yml", <<-YAML
+en:
+  foo: "1"
+      YAML
+
+      app_file 'app/models/foo.rb', <<-RUBY
+        class Foo < ActiveRecord::Base
+          @foo = I18n.t(:foo)
+        end
+      RUBY
+
+      app_file 'config/routes.rb', <<-RUBY
+        AppTemplate::Application.routes.draw do
+          match '/i18n',   :to => lambda { |env| [200, {}, [Foo.instance_variable_get('@foo')]] }
+        end
+      RUBY
+
+      require 'rack/test'
+      extend Rack::Test::Methods
+      load_app
+
+      get "/i18n"
+      assert_equal "1", last_response.body
+    end
+
     test "locales are reloaded if they change between requests" do
       add_to_config <<-RUBY
         config.cache_classes = false