RazorViewEngine cannot find partial view when running in production

[sebastianbk]

Ever since upgrading from ASP.NET Core 1.1 to 2.0 I have been running into a bunch of weird issues that I can only reproduce in production and not on my local dev environment. This latest issue is related to RazorViewEngine and, when using it to render a partial view, it complains that it cannot find the view.

This problem only occurs when running in production. When I am running the exact same code locally on IIS Express (with Visual Studio 2017 v15.3), it works as intended.

Please see the application logs and the stack trace, which I pulled from my Azure App Service log stream.

The exception is being thrown in a class I made inspired by this blog post. When I was running ASP.NET Core 1.1, this worked well in production. So I am really confused about why this is happening, especially when considering I can't reproduce it locally.

I checked up on the docs on Razor view compilation and tried setting MvcRazorCompileOnPublish to false. This fixed the issue but it is not really a fix I am happy with. How come partial views aren't included in the implicit precompiling when publishing?

2017-08-23 07:34:48.114 +00:00 [Debug] Microsoft.AspNetCore.Mvc.Razor.RazorViewEngine: View lookup cache hit for view 'Models/_InputRow' in controller '(null)'.
2017-08-23 07:34:48.114 +00:00 [Information] Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker: Executed action Sensomind.Web.Controllers.ModelsController.GetMoreInputs (Sensomind.Web) in 22.2466ms
2017-08-23 07:34:48.160 +00:00 [Error] Microsoft.AspNetCore.Diagnostics.ExceptionHandlerMiddleware: An unhandled exception has occurred: Value cannot be null.
Parameter name: Models/_InputRow does not match any available view.
System.ArgumentNullException: Value cannot be null.
Parameter name: Models/_InputRow does not match any available view.
   at Sensomind.Web.Helpers.ViewRenderService.<RenderToStringAsync>d__6.MoveNext() in d:\a\1\s\src\Sensomind.Web\Helpers\ViewRenderService.cs:line 51
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Sensomind.Web.Controllers.ModelsController.<GetMoreInputs>d__25.MoveNext() in d:\a\1\s\src\Sensomind.Web\Controllers\ModelsController.cs:line 534
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.<InvokeActionMethodAsync>d__12.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.GetResult()
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.<InvokeNextActionFilterAsync>d__10.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.Rethrow(ActionExecutedContext context)
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.<InvokeInnerFilterAsync>d__14.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.GetResult()
   at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.<InvokeNextResourceFilter>d__22.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.Rethrow(ResourceExecutedContext context)
   at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.<InvokeFilterPipelineAsync>d__17.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.GetResult()
   at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.<InvokeAsync>d__15.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.GetResult()
   at Microsoft.AspNetCore.Builder.RouterMiddleware.<Invoke>d__4.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Sensomind.Web.Startup.<>c.<<Configure>b__13_0>d.MoveNext() in d:\a\1\s\src\Sensomind.Web\Startup.cs:line 219
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at WebMarkupMin.AspNetCore2.WebMarkupMinMiddleware.<Invoke>d__5.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.GetResult()
   at Microsoft.AspNetCore.Builder.Extensions.MapMiddleware.<Invoke>d__3.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.GetResult()
   at Microsoft.AspNetCore.Session.SessionMiddleware.<Invoke>d__9.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at Microsoft.AspNetCore.Session.SessionMiddleware.<Invoke>d__9.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.GetResult()
   at Microsoft.AspNetCore.Authentication.AuthenticationMiddleware.<Invoke>d__6.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.GetResult()
   at Microsoft.AspNetCore.Diagnostics.ExceptionHandlerMiddleware.<Invoke>d__6.MoveNext()

[pranavkm]

@sebastianbk this is a variant of aspnet/Mvc#6672. Essentially the PhysicalFIleProvider does some additional work with path resolution which we don't currently do as part of precompiled views (or EmbeddedFileProvider). I detailed your problem here: aspnet/Mvc#6672 (comment)

For the time being, here's my recommended workaround:

• Modify RenderToStringAsync to use GetView in addition to FindView to resolve views. This is essentially what Mvc does when you do return View(). See https://github.com/aspnet/Mvc/blob/dev/src/Microsoft.AspNetCore.Mvc.ViewFeatures/Internal/ViewResultExecutor.cs#L79-L84 for the pattern to use. I'm planning on updating our sample for views -> string today to show the right pattern (Update RenderViewToString to use GetView \ FindView fallback Entropy#260).

• Pass in a path to RenderToStringAsync. So you have RenderVIewToString("/Views/Models/_InputRow.cshtml").

If you'd like to keep your implementation of IViewRenderService as is, you could register a IViewLocationExpander that injects a search location without the controller: /Views/{0}.cshtml,

[Eilon]

Closing because this is covered by aspnet/Mvc#6672.

[alexsorokoletov]

And I thought I'm going nuts... Thank you for opening and tracking this issue.