Resolving Optimizely CMS error "InvalidOperationException: The view 'Bootstrapper' was not found."

Bootstrapper errors are not very common during development in Optimizely CMS but they do occur on special occasions.

Typically they are caused by shifting between branches during devlopment, or when some bad harge happend and the compile directory wasn't properly cleansed after that merge.

Possible solution

If the above seems like you try to clean your directories using 

dotnet clean

The error message

Error header

An unhandled exception occurred while processing the request.
InvalidOperationException: The view 'Bootstrapper' was not found. The following locations were searched:
CmsUIViews/Views/DefaultShellModule/Bootstrapper.cshtml
/CmsDefault/CmsUIViews/Views/DefaultShellModule/Bootstrapper.cshtml
CmsUIViews/Views/Shared/Bootstrapper.cshtml
/CmsDefault/CmsUIViews/Views/Shared/Bootstrapper.cshtml
CmsUIViews/Pages/Shared/Bootstrapper.cshtml
/CmsDefault/CmsUIViews/Pages/Shared/Bootstrapper.cshtml
CmsUIViews/Util
/CmsDefault/CmsUIViews/Uti

Error Stack

InvalidOperationException: The view 'Bootstrapper' was not found. The following locations were searched: CmsUIViews/Views/DefaultShellModule/Bootstrapper.cshtml /CmsDefault/CmsUIViews/Views/DefaultShellModule/Bootstrapper.cshtml CmsUIViews/Views/Shared/Bootstrapper.cshtml /CmsDefault/CmsUIViews/Views/Shared/Bootstrapper.cshtml CmsUIViews/Pages/Shared/Bootstrapper.cshtml /CmsDefault/CmsUIViews/Pages/Shared/Bootstrapper.cshtml CmsUIViews/Util /CmsDefault/CmsUIViews/Util
Microsoft.AspNetCore.Mvc.ViewEngines.ViewEngineResult.EnsureSuccessful(IEnumerable originalLocations)
Microsoft.AspNetCore.Mvc.ViewFeatures.ViewResultExecutor.ExecuteAsync(ActionContext context, ViewResult result)
Microsoft.AspNetCore.Mvc.ViewResult.ExecuteResultAsync(ActionContext context)
Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.g__Awaited|30_0<TFilter, TFilterAsync>(ResourceInvoker invoker, Task lastTask, State next, Scope scope, object state, bool isCompleted)
Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow(ResultExecutedContextSealed context)
Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.ResultNext<TFilter, TFilterAsync>(ref State next, ref Scope scope, ref object state, ref bool isCompleted)
Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.InvokeResultFilters()
Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.g__Awaited|25_0(ResourceInvoker invoker, Task lastTask, State next, Scope scope, object state, bool isCompleted)
Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow(ResourceExecutedContextSealed context)
Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Next(ref State next, ref Scope scope, ref object state, ref bool isCompleted)
Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.InvokeFilterPipelineAsync()
Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.g__Awaited|17_0(ResourceInvoker invoker, Task task, IDisposable scope)
Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.g__Awaited|17_0(ResourceInvoker invoker, Task task, IDisposable scope)
Microsoft.AspNetCore.Routing.EndpointMiddleware.g__AwaitRequestTask|6_0(Endpoint endpoint, Task requestTask, ILogger logger)
Microsoft.AspNetCore.Authorization.Policy.AuthorizationMiddlewareResultHandler.HandleAsync(RequestDelegate next, HttpContext context, AuthorizationPolicy policy, PolicyAuthorizationResult authorizeResult)
Microsoft.AspNetCore.Authorization.AuthorizationMiddleware.Invoke(HttpContext context)
Microsoft.AspNetCore.Authentication.AuthenticationMiddleware.Invoke(HttpContext context)
Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)