add I18n support for `:placeholder` HTML option is passed to form fields

3 files changed, 40 insertions, 0 deletions

diff --git a/actionview/lib/action_view/helpers/tags/placeholderable.rb b/actionview/lib/action_view/helpers/tags/placeholderable.rb
new file mode 100644
index 0000000000..313aa725c9
--- /dev/null
+++ b/actionview/lib/action_view/helpers/tags/placeholderable.rb
@@ -0,0 +1,32 @@
+module ActionView
+  module Helpers
+    module Tags # :nodoc:
+      module Placeholderable # :nodoc:
+        def initialize(*)
+          super
+
+          if tag_value = @options[:placeholder]
+            object_name = @object_name.gsub(/\[(.*)_attributes\]\[\d+\]/, '.\1')
+            method_and_value = tag_value.is_a?(TrueClass) ? @method_name : "#{@method_name}.#{tag_value}"
+
+            if object.respond_to?(:to_model)
+              key = object.class.model_name.i18n_key
+              i18n_default = ["#{key}.#{method_and_value}".to_sym, ""]
+            end
+
+            i18n_default ||= ""
+            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)
+                        end
+
+            placeholder ||= @method_name.humanize
+
+            @options[:placeholder] = placeholder
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/actionview/lib/action_view/helpers/tags/text_area.rb b/actionview/lib/action_view/helpers/tags/text_area.rb
index 9ee83ee7c2..69038c1498 100644
--- a/actionview/lib/action_view/helpers/tags/text_area.rb
+++ b/actionview/lib/action_view/helpers/tags/text_area.rb
@@ -1,7 +1,11 @@
+require 'action_view/helpers/tags/placeholderable'
+
 module ActionView
   module Helpers
     module Tags # :nodoc:
       class TextArea < Base # :nodoc:
+        include Placeholderable
+
         def render
           options = @options.stringify_keys
           add_default_name_and_id(options)
diff --git a/actionview/lib/action_view/helpers/tags/text_field.rb b/actionview/lib/action_view/helpers/tags/text_field.rb
index e0b80d81c2..5c576a20ca 100644
--- a/actionview/lib/action_view/helpers/tags/text_field.rb
+++ b/actionview/lib/action_view/helpers/tags/text_field.rb
@@ -1,7 +1,11 @@
+require 'action_view/helpers/tags/placeholderable'
+
 module ActionView
   module Helpers
     module Tags # :nodoc:
       class TextField < Base # :nodoc:
+        include Placeholderable
+
         def render
           options = @options.stringify_keys
           options["size"] = options["maxlength"] unless options.key?("size")