Do not silently fail to generate a cache_version

When an `updated_at` column exists on the model, but is not available on the instance (likely due to a select), we should raise an error rather than silently not generating a cache_version. Without this behavior it's likely that cache entries will not be able to be invalidated and this will happen without notice. 

This behavior was reported and described by @lsylvester in https://github.com/rails/rails/pull/34197#issuecomment-429668759.

1 files changed, 8 insertions, 0 deletions

diff --git a/activerecord/test/cases/cache_key_test.rb b/activerecord/test/cases/cache_key_test.rb
index 535511d1cb..3a06b1c795 100644
--- a/activerecord/test/cases/cache_key_test.rb
+++ b/activerecord/test/cases/cache_key_test.rb
@@ -119,5 +119,13 @@ module ActiveRecord
         record_from_db.cache_version
       end
     end
+
+    test "updated_at on class but not on instance raises an error" do
+      record = CacheMeWithVersion.create
+      record_from_db = CacheMeWithVersion.where(id: record.id).select(:id).first
+      assert_raises(ActiveModel::MissingAttributeError) do
+        record_from_db.cache_version
+      end
+    end
   end
 end