`ActiveRecord::Base#becomes` should retain the errors of the original object.

This commit contains a simple failing test that demonstrates the behaviour we expect, and a fix. When using `becomes` to transform the type of an object, it should retain any error information that was present on the original instance.

2 files changed, 9 insertions, 0 deletions

diff --git a/activerecord/lib/active_record/persistence.rb b/activerecord/lib/active_record/persistence.rb
index 5e65e46a7d..f047a1d9fa 100644
--- a/activerecord/lib/active_record/persistence.rb
+++ b/activerecord/lib/active_record/persistence.rb
@@ -114,6 +114,7 @@ module ActiveRecord
       became.instance_variable_set("@attributes_cache", @attributes_cache)
       became.instance_variable_set("@new_record", new_record?)
       became.instance_variable_set("@destroyed", destroyed?)
+      became.instance_variable_set("@errors", errors)
       became.type = klass.name unless self.class.descends_from_active_record?
       became
     end
diff --git a/activerecord/test/cases/base_test.rb b/activerecord/test/cases/base_test.rb
index fdb656fe13..997c9e7e9d 100644
--- a/activerecord/test/cases/base_test.rb
+++ b/activerecord/test/cases/base_test.rb
@@ -1761,6 +1761,14 @@ class BasicsTest < ActiveRecord::TestCase
     assert_equal "The First Topic", topics(:first).becomes(Reply).title
   end
 
+  def test_becomes_includes_errors
+    company = Company.new(:name => nil)
+    assert !company.valid?
+    original_errors = company.errors
+    client = company.becomes(Client)
+    assert_equal original_errors, client.errors
+  end
+
   def test_silence_sets_log_level_to_error_in_block
     original_logger = ActiveRecord::Base.logger
     log = StringIO.new