Make sure annotate_rendered_view_with_filenames is configured

Action View is setup to copy the configuration from the application after
initialization is finished, using `ActiveSupport.on_load(:action_view)`
to make sure it only happens when `ActionView::Base` is loaded.

We need to add our on_load hook after that, so we're also putting it in
an after_initialize. Typically apps load all Rails railties before
requiring gems with Bundler, so our after_initialize should always run
after the one from Action View.

lib/better_html/railtie.rb

@@ -6,10 +6,13 @@ module BetterHtml
   class Railtie < Rails::Railtie
     initializer "better_html.better_erb.initialization" do
       BetterHtml::BetterErb.prepend!
+    end
 
+    config.after_initialize do
       ActiveSupport.on_load(:action_view) do
         BetterHtml.config.annotate_rendered_view_with_filenames = ActionView::Base.annotate_rendered_view_with_filenames
       end
     end
   end
 end
+

test/better_html/railtie_test.rb

@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+# setup dummy app
+ENV["RAILS_ENV"] ||= "test"
+require_relative "../dummy/config/environment"
+# load railtie
+require "test_helper"
+
+module BetterHtml
+  class RailtieTest < ActiveSupport::TestCase
+    test "configuration is copied from ActionView" do
+      _ = ActionView::Base
+      assert BetterHtml.config.annotate_rendered_view_with_filenames
+    end
+  end
+end