Allow the use of %{attribute} or %{model} in i18n translations.

Fix a bug where shoulda was raising an exception, when a translation
in en.yml was modified to include %{attribute} or %{model}

NEWS.md

@@ -1,5 +1,7 @@
 # HEAD
 
+* Fixes the issue where using %{attribute} or %{model} in I18n translations
+raised exceptions
 * Support datetime columns in `validate_uniqueness_of.scoped_to`
 * Add `allow_nil` option to the `validate_uniqueness_of` matcher
 

lib/shoulda/matchers/active_model/ensure_length_of_matcher.rb

@@ -104,6 +104,7 @@ module Shoulda # :nodoc:
           if Symbol === @short_message
             @short_message = default_error_message(@short_message,
                                                    :model_name => @subject.class.to_s.underscore,
+                                                   :instance => @subject,
                                                    :attribute => @attribute,
                                                    :count => @options[:minimum])
           end
@@ -111,6 +112,7 @@ module Shoulda # :nodoc:
           if Symbol === @long_message
             @long_message = default_error_message(@long_message,
                                                   :model_name => @subject.class.to_s.underscore,
+                                                  :instance => @subject,
                                                   :attribute => @attribute,
                                                   :count => @options[:maximum])
           end

lib/shoulda/matchers/active_model/helpers.rb

@@ -26,7 +26,7 @@ module Shoulda # :nodoc:
           instance = options.delete(:instance)
 
           if instance && instance.errors.respond_to?(:generate_message)
-            instance.errors.generate_message(attribute.to_sym, key, {})
+            instance.errors.generate_message(attribute.to_sym, key, options)
           else
             default_translation = [ :"activerecord.errors.models.#{model_name}.#{key}",
                                     :"activerecord.errors.messages.#{key}",

spec/shoulda/matchers/active_model/ensure_length_of_matcher_spec.rb

@@ -105,6 +105,52 @@ describe Shoulda::Matchers::ActiveModel::EnsureLengthOfMatcher do
     end
   end
 
+  context 'using translations' do
+    after { I18n.backend.reload! }
+
+    context "a too_long translation containing %{attribute}, %{model}" do
+      before do
+        stub_translation(
+          "activerecord.errors.messages.too_long",
+          "The %{attribute} of your %{model} is too long (maximum is %{count} characters)")
+      end
+
+      it "does not raise an exception" do
+        expect {
+          validating_length(:maximum => 4).should ensure_length_of(:attr).is_at_most(4)
+        }.to_not raise_exception(I18n::MissingInterpolationArgument)
+      end
+    end
+
+    context "a too_short translation containing %{attribute}, %{model}" do
+      before do
+        stub_translation(
+          "activerecord.errors.messages.too_short",
+          "The %{attribute} of your %{model} is too short (minimum is %{count} characters)")
+      end
+
+      it "does not raise an exception" do
+        expect {
+          validating_length(:minimum => 4).should ensure_length_of(:attr).is_at_least(4)
+        }.to_not raise_exception(I18n::MissingInterpolationArgument)
+      end
+    end
+
+    context "a wrong_length translation containing %{attribute}, %{model}" do
+      before do
+        stub_translation(
+          "activerecord.errors.messages.wrong_length",
+          "The %{attribute} of your %{model} is the wrong length (should be %{count} characters)")
+      end
+
+      it "does not raise an exception" do
+        expect {
+          validating_length(:is => 4).should ensure_length_of(:attr).is_equal_to(4)
+        }.to_not raise_exception(I18n::MissingInterpolationArgument)
+      end
+    end
+  end
+
   def validating_length(options = {})
     define_model(:example, :attr => :string) do
       validates_length_of :attr, options

spec/shoulda/matchers/active_model/validate_presence_of_matcher_spec.rb

@@ -82,6 +82,22 @@ describe Shoulda::Matchers::ActiveModel::ValidatePresenceOfMatcher do
     end
   end
 
+  context "an i18n translation containing %{attribute} and %{model}" do
+    before do
+      stub_translation(
+        "activerecord.errors.messages.blank",
+        "Please enter a %{attribute} for your %{model}")
+    end
+
+    after { I18n.backend.reload! }
+
+    it "does not raise an exception" do
+      expect {
+        validating_presence.should validate_presence_of(:attr)
+      }.to_not raise_exception
+    end
+  end
+
   if active_model_3_2?
     context 'a strictly required attribute' do
       it 'accepts when the :strict options match' do

spec/support/i18n_faker.rb

@@ -0,0 +1,10 @@
+module I18nFaker
+  def stub_translation(key, message)
+    yml =  key.split('.').reverse.inject(message) { |a, n| { n => a } }
+    I18n.backend.store_translations(:en, yml)
+  end
+end
+
+RSpec.configure do |config|
+  config.include I18nFaker
+end