just use the placeholder tag value if it is passed as a String

actionview/lib/action_view/helpers/tags/placeholderable.rb

@@ -6,6 +6,8 @@ def initialize(*)
           super
 
           if tag_value = @options[:placeholder]
+            placeholder = tag_value if tag_value.is_a?(String)
+
             object_name = @object_name.gsub(/\[(.*)_attributes\]\[\d+\]/, '.\1')
             method_and_value = tag_value.is_a?(TrueClass) ? @method_name : "#{@method_name}.#{tag_value}"
 
@@ -15,7 +17,7 @@ def initialize(*)
             end
 
             i18n_default ||= ""
-            placeholder = I18n.t("#{object_name}.#{method_and_value}", :default => i18n_default, :scope => "helpers.placeholder").presence
+            placeholder ||= I18n.t("#{object_name}.#{method_and_value}", :default => i18n_default, :scope => "helpers.placeholder").presence
 
             placeholder ||= if object && object.class.respond_to?(:human_attribute_name)
                           object.class.human_attribute_name(method_and_value)

actionview/test/template/form_helper_test.rb

@@ -344,15 +344,21 @@ def test_text_field_placeholder_with_human_attribute_name
     end
   end
 
+  def test_text_field_placeholder_with_string_value
+    with_locale :placeholder do
+      assert_dom_equal('<input id="post_cost" name="post[cost]" placeholder="HOW MUCH?" type="text" />', text_field(:post, :cost, placeholder: "HOW MUCH?"))
+    end
+  end
+
   def test_text_field_placeholder_with_human_attribute_name_and_value
     with_locale :placeholder do
-      assert_dom_equal('<input id="post_cost" name="post[cost]" placeholder="Pounds" type="text" />', text_field(:post, :cost, placeholder: "uk"))
+      assert_dom_equal('<input id="post_cost" name="post[cost]" placeholder="Pounds" type="text" />', text_field(:post, :cost, placeholder: :uk))
     end
   end
 
   def test_text_field_placeholder_with_locales_and_value
     with_locale :placeholder do
-      assert_dom_equal('<input id="post_written_on" name="post[written_on]" placeholder="Escrito en" type="text" value="2004-06-15" />', text_field(:post, :written_on, placeholder: "spanish"))
+      assert_dom_equal('<input id="post_written_on" name="post[written_on]" placeholder="Escrito en" type="text" value="2004-06-15" />', text_field(:post, :written_on, placeholder: :spanish))
     end
   end
 
@@ -783,11 +789,20 @@ def test_text_area_placeholder_with_human_attribute_name
     end
   end
 
+  def test_text_area_placeholder_with_string_value
+    with_locale :placeholder do
+      assert_dom_equal(
+        %{<textarea id="post_cost" name="post[cost]" placeholder="HOW MUCH?">\n</textarea>},
+        text_area(:post, :cost, placeholder: "HOW MUCH?")
+      )
+    end
+  end
+
   def test_text_area_placeholder_with_human_attribute_name_and_value
     with_locale :placeholder do
       assert_dom_equal(
         %{<textarea id="post_cost" name="post[cost]" placeholder="Pounds">\n</textarea>},
-        text_area(:post, :cost, placeholder: "uk")
+        text_area(:post, :cost, placeholder: :uk)
       )
     end
   end
@@ -796,7 +811,7 @@ def test_text_area_placeholder_with_locales_and_value
     with_locale :placeholder do
       assert_dom_equal(
         %{<textarea id="post_written_on" name="post[written_on]" placeholder="Escrito en">\n2004-06-15</textarea>},
-        text_area(:post, :written_on, placeholder: "spanish")
+        text_area(:post, :written_on, placeholder: :spanish)
       )
     end
   end