add Cell::Translation. fixes #319. many thanks to @johnlane for fixin…

…g all this.

CHANGES.md

@@ -1,6 +1,7 @@
 ## 4.0.3
 
 * `Cell::Partial` now does _append_ the global partial path to its `view_paths` instead of using `unshift` and thereby removing possible custom paths.
+* Adding `Cell::Translation` which allows using the `#t` helper. Thanks to @johnlane.
 
 ## 4.0.2
 

lib/cell/translation.rb

@@ -0,0 +1,19 @@
+# NOTE: this will soon be moved to cells-rails.
+module Cell::Translation
+  def self.included(includer)
+    super
+    includer.inheritable_attr :translation_path
+  end
+
+  def initialize(*)
+    super
+    @virtual_path = translation_path
+  end
+
+private
+  # If you override this to change this path, please report it on the trailblazer/chat gitter channel,
+  # so we can find out best practices.
+  def translation_path
+    self.class.translation_path or controller_path.gsub("/", ".")
+  end
+end

test/rails/translation_test.rb

@@ -0,0 +1,45 @@
+require "test_helper"
+require "cells/translation"
+
+class TranslationTest < MiniTest::Spec
+  class I18nCell < Cell::ViewModel
+    include ActionView::Helpers::TranslationHelper
+    include Translation
+
+    def greet_relative
+      t(".greeting") # gets appended to translation_test.i18n.
+    end
+
+    def greet_absolute
+      t("translation_test.i18n.greeting")
+    end
+  end
+
+  I18n.backend = I18n::Backend::KeyValue.new({})
+  I18n.backend.store_translations(:en,
+                                  { "translation_test.i18n.greeting" => "Translated!",
+                                    "cell.friendly.greeting" => "Hello you!" },
+                                  escape: false)
+
+  # Translate text specified by an absolute path
+  it { I18nCell.new.greet_absolute.must_equal "Translated!" }
+
+  # Translate text specified by an relative path
+  it { I18nCell.new.greet_relative.must_equal "Translated!" }
+
+
+  describe "::translation_path" do
+      class ExplicitI18NCell < Cell::ViewModel
+      include ActionView::Helpers::TranslationHelper
+      include Translation
+
+      self.translation_path = "cell.friendly"
+
+      def show
+        t(".greeting")
+      end
+    end
+
+    it { ExplicitI18NCell.new.().must_equal "Hello you!" }
+  end
+end