Merge pull request #696 from KinWang-2013/fix/exists-method-nil-key

[FIX] Raise ArgumentError on nil key in exists?

lib/i18n.rb

@@ -265,7 +265,8 @@ def interpolation_keys(key, **options)
     def exists?(key, _locale = nil, locale: _locale, **options)
       locale ||= config.locale
       raise Disabled.new('exists?') if locale == false
-      raise I18n::ArgumentError if key.is_a?(String) && key.empty?
+      raise I18n::ArgumentError if (key.is_a?(String) && key.empty?) || key.nil?
+
       config.backend.exists?(locale, key, options)
     end
 

test/i18n_test.rb

@@ -315,6 +315,10 @@ def setup
     assert_raises(I18n::ArgumentError) { I18n.interpolation_keys(["bad-argument"]) }
   end
 
+  test "exists? given nil raises I18n::ArgumentError" do
+    assert_raises(I18n::ArgumentError) { I18n.exists?(nil) }
+  end
+
   test "exists? given an existing key will return true" do
     assert_equal true, I18n.exists?(:currency)
   end