Fall back to english on MissingInterpolationError

config/initializers/locale.rb

@@ -14,3 +14,5 @@ AVAILABLE_LANGUAGE_CODES.each do |c|
     I18n.fallbacks[c.to_sym] = [c.to_sym, DEFAULT_LANGUAGE.to_sym, :en]
   end
 end
+require 'i18n_interpolation_fallbacks'
+I18n::Backend::Simple.send(:include, I18n::Backend::InterpolationFallbacks)

lib/i18n_interpolation_fallbacks.rb

+module I18n
+  module Backend
+    module InterpolationFallbacks
+
+      def translate(locale, key, options = {})
+        return super if options[:fallback]
+        default = extract_string_or_lambda_default!(options) if options[:default]
+
+        options[:fallback] = true
+        I18n.fallbacks[locale].each do |fallback|
+          begin
+            result = super(fallback, key, options)
+            return result unless result.nil?
+          rescue I18n::MissingInterpolationArgument
+          end
+        end
+        options.delete(:fallback)
+
+        return super(locale, nil, options.merge(:default => default)) if default
+        raise(I18n::MissingInterpolationError.new(locale, key, options))
+      end
+    end
+  end
+end

spec/misc_spec.rb

@@ -62,4 +62,19 @@ describe 'making sure the spec runner works' do
     end
   end
 
+  describe I18n do
+    include ActionView::Helpers::TranslationHelper
+    it 'MissingInterpolationError in a non-english locale is not fatal' do
+      I18n.locale = 'it'
+      I18n.backend.should_receive(:lookup).ordered.
+        with(:it, 'bob', nil, :hey => "what", :fallback => true).
+        and_return("%{not_present} failure")
+      I18n.backend.should_receive(:lookup).ordered.
+        with(:en, 'bob', nil, :hey => "what", :fallback => true).
+        and_return("English translation")
+      translation = translate('bob', :hey => "what")
+      translation.should == "English translation"
+    end
+  end
+
 end