experimental backend/cache implementation

lib/i18n/backend/cache.rb

@@ -0,0 +1,54 @@
+# This module allows you to easily cache all responses from the backend - thus
+# speeding up the I18n aspects of your application quite a bit.
+#
+# To enable caching you can simply include the Cache module to the Simple
+# backend - or whatever other backend you are using:
+#
+#  I18n::Backend::Simple.send(:include, I18n::Backend::Cache)
+#
+# You will also need to set a cache store implementation that you want to use:
+#
+#  I18n.cache_store = ActiveSupport::Cache.lookup_store(:memory_store)
+#
+# You can use any cache implementation you want that provides the same API as
+# the ActiveSupport::Cache API. 
+module I18n
+  class << self
+    @@cache_store = nil
+
+    def cache_store
+      @@cache_store
+    end
+
+    def cache_store=(store)
+      @@cache_store = store
+    end
+
+    def perform_caching?
+      !cache_store.nil?
+    end
+  end
+
+  module Backend
+    module Cache
+      def translate(*args)
+        I18n.perform_caching? ? fetch(*args) { super } : super
+      end
+
+      protected
+
+        def fetch(*args, &block)
+          result = I18n.cache_store.fetch(cache_key(*args), &block)
+          raise result if result.is_a?(Exception)
+          result
+        rescue MissingTranslationData => exception
+          I18n.cache_store.write(cache_key(*args), exception)
+          raise exception
+        end
+
+        def cache_key(*args)
+          args.hash
+        end
+    end
+  end
+end

test/backend/cache/cache_test.rb

@@ -0,0 +1,35 @@
+require File.expand_path(File.dirname(__FILE__) + '/../../test_helper')
+require 'i18n/backend/cache'
+require 'activesupport'
+
+class I18nCacheBackendTest < Test::Unit::TestCase
+  def setup
+    super
+    class << I18n.backend
+      include I18n::Backend::Cache
+    end
+    I18n.cache_store = ActiveSupport::Cache.lookup_store(:memory_store)
+  end
+
+  def teardown
+    I18n.cache_store = nil
+  end
+
+  define_method :"test translate hits the backend and caches the response" do
+    I18n.backend.expects(:lookup).returns('Foo')
+    assert_equal 'Foo', I18n.t(:foo)
+
+    I18n.backend.expects(:lookup).never
+    assert_equal 'Foo', I18n.t(:foo)
+
+    I18n.backend.expects(:lookup).returns('Bar')
+    assert_equal 'Bar', I18n.t(:bar)
+  end
+
+  define_method :"test still raises MissingTranslationData but also caches it" do
+    I18n.backend.expects(:lookup).returns(nil)
+    assert_raises(I18n::MissingTranslationData) { I18n.t(:missing, :raise => true) }
+    I18n.backend.expects(:lookup).never
+    assert_raises(I18n::MissingTranslationData) { I18n.t(:missing, :raise => true) }
+  end
+end