Add deprecation message

README.md

@@ -280,8 +280,13 @@ end
 | `host_locales` | Sets `I18n.locale` based on `request.host`. Useful for apps accepting requests from more than one domain. See below for more details | `{}` |
 | `locale_param_key` | The param key used to set the locale to the newly generated routes | `:locale` |
 | `locale_segment_proc` | The locale segment of the url will by default be `locale.to_s.downcase`. You can supply your own mechanism via a Proc that takes `locale` as an argument, e.g. `->(locale) { locale.to_s.upcase }` | `false` |
-| `i18n_use_controller_path` | Use the exact controller path `account/foo` for looking up translations instead of nested keys `account.foo` | `false` |
+| `i18n_use_slash_separator` | Use the exact controller path `account/foo` for looking up translations instead of nested keys `account.foo` | `false` |
 
+#### Deprecated options
+
+- `i18n_use_slash_separator` is deprecated and will be forced to `true` in the next major release of Route Translator. This only
+  affects application with nested routes. Please set this option to `true` to remove the deprecation message and ensure
+  to convert nested routes like `people.products` to the new `people/products`.
 
 ### Host-based Locale
 

lib/route_translator.rb

@@ -21,7 +21,7 @@ module RouteTranslator
     host_locales:                        {},
     locale_param_key:                    :locale,
     locale_segment_proc:                 false,
-    i18n_use_controller_path:            false
+    i18n_use_slash_separator:            false
   }.freeze
 
   Configuration = Struct.new(*DEFAULT_CONFIGURATION.keys)
@@ -35,6 +35,18 @@ def resolve_host_locale_config_conflicts
       @config.generate_unnamed_unlocalized_routes = false
       @config.hide_locale                         = true
     end
+
+    def check_deprecations
+      return if @config.i18n_use_slash_separator
+
+      ActiveSupport::Deprecation.warn <<~MSG
+        `i18n_use_slash_separator` set to `false` is deprecated and will be
+        removed in the next major release of Route Translator to match
+        Rails' ActiveRecord nested model syntax.
+
+        More information at https://github.com/enriclluelles/route_translator/pull/285
+      MSG
+    end
   end
 
   module_function
@@ -49,6 +61,7 @@ def config
     yield @config if block_given?
 
     resolve_host_locale_config_conflicts if @config.host_locales.present?
+    check_deprecations
 
     @config
   end

lib/route_translator/route.rb

@@ -16,7 +16,7 @@ def initialize(route_set, path, name, options_constraints, options, mapping)
     def scope
       @scope ||=
         if mapping.defaults[:controller]
-          if RouteTranslator.config.i18n_use_controller_path
+          if RouteTranslator.config.i18n_use_slash_separator
             %i[routes controllers].push mapping.defaults[:controller]
           else
             %i[routes controllers].concat mapping.defaults[:controller].split('/').map(&:to_sym)

test/integration/i18n_slash_separator_test.rb

@@ -0,0 +1,33 @@
+# frozen_string_literal: true
+
+require 'test_helper'
+
+class I18nSlashSeparatorTest < ActionDispatch::IntegrationTest
+  include RouteTranslator::ConfigurationHelper
+
+  def teardown
+    teardown_config
+  end
+
+  def test_deprecation_when_default
+    assert_deprecated('i18n_use_slash_separator') do
+      RouteTranslator.config
+    end
+  end
+
+  def test_deprecation_when_false
+    config_i18n_use_slash_separator false
+
+    assert_deprecated('i18n_use_slash_separator') do
+      RouteTranslator.config
+    end
+  end
+
+  def test_no_deprecation_when_true
+    config_i18n_use_slash_separator true
+
+    assert_not_deprecated do
+      RouteTranslator.config
+    end
+  end
+end

test/routing_test.rb

@@ -159,7 +159,7 @@ def test_namespaced_resources
   end
 
   def test_controller_namespaced_resources
-    config_i18n_use_controller_path(true)
+    config_i18n_use_slash_separator(true)
     I18n.default_locale = :es
 
     draw_routes do