Use round(scale) in ActiveModel NumericalityValidator

activemodel/lib/active_model/validations/numericality.rb

@@ -71,6 +71,8 @@ def parse_as_number(raw_value, precision, scale, option = nil)
           raw_value if raw_value.is_a?(Range)
         elsif raw_value.is_a?(Float)
           parse_float(raw_value, precision, scale)
+        elsif raw_value.is_a?(BigDecimal)
+          round(raw_value, scale)
         elsif raw_value.is_a?(Numeric)
           raw_value
         elsif is_integer?(raw_value)
@@ -81,7 +83,11 @@ def parse_as_number(raw_value, precision, scale, option = nil)
       end
 
       def parse_float(raw_value, precision, scale)
-        (scale ? raw_value.truncate(scale) : raw_value).to_d(precision)
+        round(raw_value, scale).to_d(precision)
+      end
+
+      def round(raw_value, scale)
+        scale ? raw_value.round(scale) : raw_value
       end
 
       def is_number?(raw_value, precision, scale)

activerecord/test/cases/validations/numericality_validation_test.rb

@@ -103,6 +103,21 @@ def test_virtual_attribute_with_scale
     assert_not_predicate subject, :valid?
   end
 
+  def test_virtual_attribute_with_precision_and_scale
+    model_class.attribute(:virtual_decimal_number, :decimal, precision: 4, scale: 2)
+    model_class.validates_numericality_of(
+      :virtual_decimal_number, less_than_or_equal_to: 99.99
+    )
+
+    subject = model_class.new(virtual_decimal_number: 99.994)
+    assert_equal 99.99.to_d(4), subject.virtual_decimal_number
+    assert_predicate subject, :valid?
+
+    subject = model_class.new(virtual_decimal_number: 99.999)
+    assert_equal 100.00.to_d(4), subject.virtual_decimal_number
+    assert_not_predicate subject, :valid?
+  end
+
   def test_aliased_attribute
     model_class.validates_numericality_of(:new_bank_balance, greater_or_equal_than: 0)
 

activerecord/test/cases/validations_test.rb

@@ -187,9 +187,17 @@ def self.model_name
       validates_numericality_of :wibble, greater_than_or_equal_to: BigDecimal("97.18")
     end
 
-    assert_not_predicate klass.new(wibble: "97.179"), :valid?
-    assert_not_predicate klass.new(wibble: 97.179), :valid?
-    assert_not_predicate klass.new(wibble: BigDecimal("97.179")), :valid?
+    ["97.179", 97.179, BigDecimal("97.179")].each do |raw_value|
+      subject = klass.new(wibble: raw_value)
+      assert_equal 97.18.to_d(4), subject.wibble
+      assert_predicate subject, :valid?
+    end
+
+    ["97.174", 97.174, BigDecimal("97.174")].each do |raw_value|
+      subject = klass.new(wibble: raw_value)
+      assert_equal 97.17.to_d(4), subject.wibble
+      assert_not_predicate subject, :valid?
+    end
   end
 
   def test_numericality_validator_wont_be_affected_by_custom_getter