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, 11 insertions, 6 deletions

diff --git a/activerecord/lib/active_record/integration.rb b/activerecord/lib/active_record/integration.rb
index 43f6afbb42..db7200bceb 100644
--- a/activerecord/lib/active_record/integration.rb
+++ b/activerecord/lib/active_record/integration.rb
@@ -97,13 +97,18 @@ module ActiveRecord
     # +false+ (which it is by default until Rails 6.0).
     def cache_version
       return unless cache_versioning
-      return unless has_attribute?("updated_at")
 
-      timestamp = updated_at_before_type_cast
-      if can_use_fast_cache_version?(timestamp)
-        raw_timestamp_to_cache_version(timestamp)
-      elsif timestamp = updated_at
-        timestamp.utc.to_s(cache_timestamp_format)
+      if has_attribute?("updated_at")
+        timestamp = updated_at_before_type_cast
+        if can_use_fast_cache_version?(timestamp)
+          raw_timestamp_to_cache_version(timestamp)
+        elsif timestamp = updated_at
+          timestamp.utc.to_s(cache_timestamp_format)
+        end
+      else
+        if self.class.has_attribute?("updated_at")
+          raise ActiveModel::MissingAttributeError, "missing attribute: updated_at"
+        end
       end
     end