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 #34197 (comment).

activerecord/lib/active_record/integration.rb

@@ -97,13 +97,18 @@ def cache_key(*timestamp_names)
     # +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
 

activerecord/test/cases/cache_key_test.rb

@@ -119,5 +119,13 @@ class CacheMeWithVersion < ActiveRecord::Base
         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