When the Namespace Dropdown in the Argo Rollouts Dashboard Disappeared

Introduction

In the Argo Rollouts dashboard, the NAMESPACE field had turned from a dropdown into a disabled input box. All I could see was the default namespace, and there was no way to switch somewhere else and look at other rollouts. I went through the source code, checked permissions, turned on debug logs, and after all that the culprit turned out to be a single rollout that had the wrong type in one resource field, which made the whole cluster-wide list fail to decode. Let me write down how I tracked it down.