Deprecate the :prefix option of `number_to_human_size`

activesupport/lib/active_support/number_helper.rb

@@ -220,8 +220,6 @@ def number_to_rounded(number, options = {})
     # * <tt>:strip_insignificant_zeros</tt> - If +true+ removes
     #   insignificant zeros after the decimal separator (defaults to
     #   +true+)
-    # * <tt>:prefix</tt> - If +:si+ formats the number using the SI
-    #   prefix (defaults to :binary)
     #
     # ==== Examples
     #

activesupport/lib/active_support/number_helper/number_to_human_size_converter.rb

@@ -7,6 +7,10 @@ class NumberToHumanSizeConverter < NumberConverter #:nodoc:
       self.validate_float = true
 
       def convert
+        if opts.key?(:prefix)
+          ActiveSupport::Deprecation.warn('The :prefix option of `number_to_human_size` is deprecated and will be removed in Rails 5.1 with no replacement.')
+        end
+
         @number = Float(number)
 
         # for backwards compatibility with those that didn't add strip_insignificant_zeros to their locale files