Respect scale of the column in the Decimal type

[Rafael Mendonça França + Jean Boussier]

activerecord/lib/active_record/type/decimal.rb

@@ -14,7 +14,7 @@ module ActiveRecord
       private
 
       def cast_value(value)
-        case value
+        casted_value = case value
         when ::Float
           convert_float_to_big_decimal(value)
         when ::Numeric, ::String
@@ -26,6 +26,8 @@ module ActiveRecord
             cast_value(value.to_s)
           end
         end
+
+        scale ? casted_value.round(scale) : casted_value
       end
 
       def convert_float_to_big_decimal(value)

activerecord/test/cases/base_test.rb

@@ -946,6 +946,34 @@ class BasicsTest < ActiveRecord::TestCase
     assert_equal BigDecimal("1000234000567.95"), m1.big_bank_balance
   end
 
+  def test_numeric_fields_with_scale
+    m = NumericData.new(
+      :bank_balance => 1586.43122334,
+      :big_bank_balance => BigDecimal("234000567.952344"),
+      :world_population => 6000000000,
+      :my_house_population => 3
+    )
+    assert m.save
+
+    m1 = NumericData.find(m.id)
+    assert_not_nil m1
+
+    # As with migration_test.rb, we should make world_population >= 2**62
+    # to cover 64-bit platforms and test it is a Bignum, but the main thing
+    # is that it's an Integer.
+    assert_kind_of Integer, m1.world_population
+    assert_equal 6000000000, m1.world_population
+
+    assert_kind_of Fixnum, m1.my_house_population
+    assert_equal 3, m1.my_house_population
+
+    assert_kind_of BigDecimal, m1.bank_balance
+    assert_equal BigDecimal("1586.43"), m1.bank_balance
+
+    assert_kind_of BigDecimal, m1.big_bank_balance
+    assert_equal BigDecimal("234000567.95"), m1.big_bank_balance
+  end
+
   def test_auto_id
     auto = AutoId.new
     auto.save

activerecord/test/cases/type/decimal_test.rb

@@ -25,6 +25,11 @@ module ActiveRecord
         assert_equal BigDecimal("0.33"), type.cast(Rational(1, 3))
       end
 
+      def test_type_cast_decimal_from_rational_with_precision_and_scale
+        type = Decimal.new(precision: 4, scale: 2)
+        assert_equal BigDecimal("0.33"), type.cast(Rational(1, 3))
+      end
+
       def test_type_cast_decimal_from_rational_without_precision_defaults_to_18_36
         type = Decimal.new
         assert_equal BigDecimal("0.333333333333333333E0"), type.cast(Rational(1, 3))