1 files changed, 46 insertions, 14 deletions
diff --git a/activesupport/lib/active_support/number_helper/number_to_rounded_converter.rb b/activesupport/lib/active_support/number_helper/number_to_rounded_converter.rb
index ab430bbc7a..c45f6cdcfa 100644
--- a/activesupport/lib/active_support/number_helper/number_to_rounded_converter.rb
+++ b/activesupport/lib/active_support/number_helper/number_to_rounded_converter.rb
@@ -1,45 +1,69 @@
 module ActiveSupport
   module NumberHelper
     class NumberToRoundedConverter < NumberConverter # :nodoc:
-      self.namespace        = :precision
-      self.need_valid_float = true
+      self.namespace      = :precision
+      self.validate_float = true
 
       def convert
-        @number = Float(@number)
-
         precision = options.delete :precision
         significant = options.delete :significant
 
+        case number
+        when Float, String
+          @number = BigDecimal(number.to_s)
+        when Rational
+          if significant
+            @number = BigDecimal(number, digit_count(number.to_i) + precision)
+          else
+            @number = BigDecimal(number, precision)
+          end
+        else
+          @number = number.to_d
+        end
+
         if significant && precision > 0
           digits, rounded_number = digits_and_rounded_number(precision)
           precision -= digits
           precision = 0 if precision < 0 # don't let it be negative
         else
-          rounded_number = BigDecimal.new(@number.to_s).round(precision).to_f
+          rounded_number = number.round(precision)
+          rounded_number = rounded_number.to_i if precision == 0
           rounded_number = rounded_number.abs if rounded_number.zero? # prevent showing negative zeros
         end
 
-        delimited_number = NumberToDelimitedConverter.convert("%01.#{precision}f" % rounded_number, options)
+        formatted_string =
+          if BigDecimal === rounded_number && rounded_number.finite?
+            s = rounded_number.to_s('F') + '0'*precision
+            a, b = s.split('.', 2)
+            a + '.' + b[0, precision]
+          else
+            "%01.#{precision}f" % rounded_number
+          end
+
+        delimited_number = NumberToDelimitedConverter.convert(formatted_string, options)
         format_number(delimited_number)
       end
 
       private
 
         def digits_and_rounded_number(precision)
-          return [1,0] if @number.zero?
-          digits = digit_count(@number)
-          multiplier = 10 ** (digits - precision)
-          rounded_number = calculate_rounded_number(multiplier)
-          digits = digit_count(rounded_number) # After rounding, the number of digits may have changed
-          [digits, rounded_number]
+          if zero?
+            [1, 0]
+          else
+            digits = digit_count(number)
+            multiplier = 10 ** (digits - precision)
+            rounded_number = calculate_rounded_number(multiplier)
+            digits = digit_count(rounded_number) # After rounding, the number of digits may have changed
+            [digits, rounded_number]
+          end
         end
 
         def calculate_rounded_number(multiplier)
-          (BigDecimal.new(@number.to_s) / BigDecimal.new(multiplier.to_f.to_s)).round.to_f * multiplier
+          (number / BigDecimal.new(multiplier.to_f.to_s)).round * multiplier
         end
 
         def digit_count(number)
-          (Math.log10(number.abs) + 1).floor
+          (Math.log10(absolute_number(number)) + 1).floor
         end
 
         def strip_insignificant_zeros
@@ -54,6 +78,14 @@ module ActiveSupport
             number
           end
         end
+
+        def absolute_number(number)
+          number.respond_to?(:abs) ? number.abs : number.to_d.abs
+        end
+
+        def zero?
+          number.respond_to?(:zero?) ? number.zero? : number.to_d.zero?
+        end
     end
   end
 end