Unicorn Error – There is an extends inheritance loop, or a container extending a nonexistant container name

The problem:

I faced the following issue when trying to set up Unicorn on an existing Sitecore instance. There’s no information about that on Unicorn documentation and the error isn’t clear.

The solution:

After a while, I’ve figured out that the problem was in another .config file which was set up by someone in the past to Serialize items from Forms Extensions module.

 The only tip here is the final word: “Feature.FormsExtension”.

Looking for it, I’ve found a suspicious file named Feature.FormsExtensions.Serialization.config under App_Config\Include\Feature\FormsExtensions.

Inspecting this file, we can see that the configuration name is “Feature.FormsExtension”, the same name pointed by the error.

Perhaps, you are facing the same issue but for another .config file, so check the last word at the error message, like “….Unresolved containers probably at fault: Feature.FormsExtensions”.

With this name, perform a search under App_Config looking for this name.

Here you can apply 2 solutions:

1. If this .config file doesn’t make sense for you or it’s useless in your project (make sure that), just remove or disable this .config file;
2. If this .config file is important, you will need to manually fix the error. The problem occurs because the .config file is trying to extend a Configuration placed in another .config file that doesn’t exist. In my case, this is the “Helix.Feature”. You can simply remove this extension by removing the extends=“Helix.Feature” parameter from tag because this configuration doesn’t exist anymore. But be careful, if this is important and you cannot remove it, you will need to fix those configurations because something is missing and is breaking the Unicorn. You can understand a little more on: https://kamsar.net/index.php/2017/02/Unicorn-4-Part-III-Configuration-Enhancements/

Hope it helps you!