Fixed number_with_precision rounding error [#6182 state:resolved]

actionpack/lib/action_view/helpers/number_helper.rb

@@ -270,12 +270,13 @@ def number_with_precision(number, options = {})
             digits, rounded_number = 1, 0
           else
             digits = (Math.log10(number.abs) + 1).floor
-            rounded_number = BigDecimal.new((number / 10 ** (digits - precision)).to_s).round.to_f * 10 ** (digits - precision)
+            rounded_number = (BigDecimal.new(number.to_s) / 10 ** (digits - precision)).round.to_f * 10 ** (digits - precision)
+            digits = (Math.log10(rounded_number.abs) + 1).floor # After rounding, the number of digits may have changed
           end
           precision -= digits
           precision = precision > 0 ? precision : 0  #don't let it be negative
         else
-          rounded_number = BigDecimal.new((number * (10 ** precision)).to_s).round.to_f / 10 ** precision
+          rounded_number = BigDecimal.new(number.to_s).round(precision).to_f
         end
         formatted_number = number_with_delimiter("%01.#{precision}f" % rounded_number, options)
         if strip_insignificant_zeros

actionpack/test/template/number_helper_test.rb

@@ -100,6 +100,11 @@ def test_number_with_precision
     assert_equal("0", number_with_precision(0, :precision => 0))
     assert_equal("0.00100", number_with_precision(0.001, :precision => 5))
     assert_equal("0.001", number_with_precision(0.00111, :precision => 3))
+    assert_equal("10.00", number_with_precision(9.995, :precision => 2))
+    assert_equal("11.00", number_with_precision(10.995, :precision => 2))
+    assert_equal("10.0", number_with_precision(9.995, :precision => 3, :significant => true))
+    assert_equal("9.99", number_with_precision(9.994, :precision => 3, :significant => true))
+    assert_equal("11.0", number_with_precision(10.995, :precision => 3, :significant => true))
   end
 
   def test_number_with_precision_with_custom_delimiter_and_separator