Add a deprecation cycle for `NullColumn` from `column_for_attribute`

This is public API, and `simple_form` depends on the `nil` return value.
We need to go through a deprecation cycle to return a null object. If
people want hash access, they can access the hash.

1 files changed, 4 insertions, 18 deletions

diff --git a/activerecord/test/cases/reflection_test.rb b/activerecord/test/cases/reflection_test.rb
index c6e73f78cc..acbd065649 100644
--- a/activerecord/test/cases/reflection_test.rb
+++ b/activerecord/test/cases/reflection_test.rb
@@ -80,24 +80,10 @@ class ReflectionTest < ActiveRecord::TestCase
     assert_equal :integer, @first.column_for_attribute("id").type
   end
 
-  def test_non_existent_columns_return_null_object
-    column = @first.column_for_attribute("attribute_that_doesnt_exist")
-    assert_instance_of ActiveRecord::ConnectionAdapters::NullColumn, column
-    assert_equal "attribute_that_doesnt_exist", column.name
-    assert_equal nil, column.sql_type
-    assert_equal nil, column.type
-    assert_not column.number?
-    assert_not column.text?
-    assert_not column.binary?
-  end
-
-  def test_non_existent_columns_are_identity_types
-    column = @first.column_for_attribute("attribute_that_doesnt_exist")
-    object = Object.new
-
-    assert_equal object, column.type_cast_from_database(object)
-    assert_equal object, column.type_cast_from_user(object)
-    assert_equal object, column.type_cast_for_database(object)
+  def test_non_existent_columns_return_nil
+    assert_deprecated do
+      assert_nil @first.column_for_attribute("attribute_that_doesnt_exist")
+    end
   end
 
   def test_reflection_klass_for_nested_class_name