bolero-app template using Bolero.dll (0.15.18) throws could not load Elmish 3.1.0.0 dll exception

I ran the getting started commands with the latest .NET Core SDK installed (3.1.402) on Windows 10:

dotnet new -i Bolero.Templates
dotnet new bolero-app -o MyApp
cd MyApp
dotnet run -p src/MyApp.Server

When I navigate to http://localhost:5000 I get this error in the console window:

PS C:\Users\AdamDavidson\source\repos\MyApp> dotnet run -p src/MyApp.Server
info: Microsoft.AspNetCore.DataProtection.KeyManagement.XmlKeyManager[0]
      User profile is available. Using 'C:\Users\AdamDavidson\AppData\Local\ASP.NET\DataProtection-Keys' as key repository and Windows DPAPI to encrypt keys at rest.
Hosting environment: Development
Content root path: C:\Users\AdamDavidson\source\repos\MyApp\src\MyApp.Server
Now listening on: https://localhost:5001
Now listening on: http://localhost:5000
Application started. Press Ctrl+C to shut down.
info: Microsoft.AspNetCore.Hosting.Diagnostics[1]
      Request starting HTTP/1.1 GET http://localhost:5000/
info: Microsoft.AspNetCore.Routing.EndpointMiddleware[0]
      Executing endpoint '/_Host'
info: Microsoft.AspNetCore.Mvc.RazorPages.Infrastructure.PageActionInvoker[3]
      Route matched with {page = "/_Host"}. Executing page /_Host
info: Microsoft.AspNetCore.Mvc.RazorPages.Infrastructure.PageActionInvoker[103]
      Executing an implicit handler method - ModelState is Valid
info: Microsoft.AspNetCore.Mvc.RazorPages.Infrastructure.PageActionInvoker[104]
      Executed an implicit handler method, returned result Microsoft.AspNetCore.Mvc.RazorPages.PageResult.
info: Microsoft.AspNetCore.Mvc.RazorPages.Infrastructure.PageActionInvoker[4]
      Executed page /_Host in 21.9843ms
info: Microsoft.AspNetCore.Routing.EndpointMiddleware[1]
      Executed endpoint '/_Host'
fail: Microsoft.AspNetCore.Server.Kestrel[13]
      Connection id "0HM2Q8PGCGTVF", Request id "0HM2Q8PGCGTVF:00000001": An unhandled exception was thrown by the application.
System.IO.FileLoadException: Could not load file or assembly 'Elmish, Version=3.1.0.0, Culture=neutral, PublicKeyToken=null'. The located assembly's manifest definition does not match the assembly reference. (0x80131040)
File name: 'Elmish, Version=3.1.0.0, Culture=neutral, PublicKeyToken=null'
   at MyApp.Server.Pages__Host.<ExecuteAsync>b__8_1()
   at System.Runtime.CompilerServices.AsyncMethodBuilderCore.Start[TStateMachine](TStateMachine& stateMachine)
   at MyApp.Server.Pages__Host.<ExecuteAsync>b__8_1()
   at Microsoft.AspNetCore.Razor.Runtime.TagHelpers.TagHelperExecutionContext.SetOutputContentAsync()
   at MyApp.Server.Pages__Host.ExecuteAsync()
   at Microsoft.AspNetCore.Mvc.Razor.RazorView.RenderPageCoreAsync(IRazorPage page, ViewContext context)
   at Microsoft.AspNetCore.Mvc.Razor.RazorView.RenderPageAsync(IRazorPage page, ViewContext context, Boolean invokeViewStarts)
   at Microsoft.AspNetCore.Mvc.Razor.RazorView.RenderAsync(ViewContext context)
   at Microsoft.AspNetCore.Mvc.ViewFeatures.ViewExecutor.ExecuteAsync(ViewContext viewContext, String contentType, Nullable`1 statusCode)
   at Microsoft.AspNetCore.Mvc.ViewFeatures.ViewExecutor.ExecuteAsync(ViewContext viewContext, String contentType, Nullable`1 statusCode)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeNextResultFilterAsync>g__Awaited|29_0[TFilter,TFilterAsync](ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow(ResultExecutedContextSealed context)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.ResultNext[TFilter,TFilterAsync](State& next, Scope& scope, Object& state, Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.InvokeResultFilters()
--- End of stack trace from previous location where exception was thrown ---
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeNextResourceFilter>g__Awaited|24_0(ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow(ResourceExecutedContextSealed context)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.InvokeFilterPipelineAsync()
--- End of stack trace from previous location where exception was thrown ---
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeAsync>g__Logged|17_1(ResourceInvoker invoker)
   at Microsoft.AspNetCore.Routing.EndpointMiddleware.<Invoke>g__AwaitRequestTask|6_0(Endpoint endpoint, Task requestTask, ILogger logger)
   at Microsoft.AspNetCore.Builder.Extensions.MapWhenMiddleware.Invoke(HttpContext context)
   at Microsoft.AspNetCore.Authentication.AuthenticationMiddleware.Invoke(HttpContext context)
   at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.HttpProtocol.ProcessRequests[TContext](IHttpApplication`1 application)


info: Microsoft.AspNetCore.Hosting.Diagnostics[2]
      Request finished in 6011.3861ms 500

Here is the information from dotnet --info showing the platform, sdks, frameworks installed etc.:

PS C:\Users\AdamDavidson\source\repos\MyApp> dotnet --info
.NET Core SDK (reflecting any global.json):
 Version:   3.1.402
 Commit:    9b5de826fd

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.18363
 OS Platform: Windows
 RID:         win10-x64
 Base Path:   C:\Program Files\dotnet\sdk\3.1.402\

Host (useful for support):
  Version: 3.1.8
  Commit:  9c1330dedd

.NET Core SDKs installed:
  2.1.700 [C:\Program Files\dotnet\sdk]
  3.1.201 [C:\Program Files\dotnet\sdk]
  3.1.402 [C:\Program Files\dotnet\sdk]

.NET Core runtimes installed:
  Microsoft.AspNetCore.All 2.1.11 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.1.22 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.App 2.1.11 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.1.22 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 3.1.3 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 3.1.8 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 2.1.11 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.22 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 3.1.3 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 3.1.8 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.WindowsDesktop.App 3.1.3 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 3.1.8 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

To install additional .NET Core runtimes or SDKs:
  https://aka.ms/dotnet-download

Looking at Bolero.dll (0.15.18) in dotPeek show it has a dependency on Elmish 3.1.0.0 but the package only mentions Elmish 3.0.0.0 which might be why it’s not finding the dll that Bolero.dll expects. When I add Elmish 3.1.0.0 as a nuget package explictly I get a different error, so I’ve not yet found a workaround:

System.MissingMethodException: 'Method not found: 'Void Elmish.Program`4..ctor(Microsoft.FSharp.Core.FSharpFunc`2<!0,System.Tuple`2<!1,Microsoft.FSharp.Collections.FSharpList`1<Microsoft.FSharp.Core.FSharpFunc`2<Microsoft.FSharp.Core.FSharpFunc`2<!2,Microsoft.FSharp.Core.Unit>,Microsoft.FSharp.Core.Unit>>>>, Microsoft.FSharp.Core.FSharpFunc`2<!2,Microsoft.FSharp.Core.FSharpFunc`2<!1,System.Tuple`2<!1,Microsoft.FSharp.Collections.FSharpList`1<Microsoft.FSharp.Core.FSharpFunc`2<Microsoft.FSharp.Core.FSharpFunc`2<!2,Microsoft.FSharp.Core.Unit>,Microsoft.FSharp.Core.Unit>>>>>, Microsoft.FSharp.Core.FSharpFunc`2<!1,Microsoft.FSharp.Collections.FSharpList`1<Microsoft.FSharp.Core.FSharpFunc`2<Microsoft.FSharp.Core.FSharpFunc`2<!2,Microsoft.FSharp.Core.Unit>,Microsoft.FSharp.Core.Unit>>>, Microsoft.FSharp.Core.FSharpFunc`2<!1,Microsoft.FSharp.Core.FSharpFunc`2<Microsoft.FSharp.Core.FSharpFunc`2<!2,Microsoft.FSharp.Core.Unit>,!3>>, Microsoft.FSharp.Core.FSharpFunc`2<!1,Microsoft.FSharp.Core.FSharpFunc`2<Microsoft.FSharp.Core.FSharpFunc`2<!2,Microsoft.FSharp.Core.Unit>,Microsoft.FSharp.Core.Unit>>, Microsoft.FSharp.Core.FSharpFunc`2<System.Tuple`2<System.String,System.Exception>,Microsoft.FSharp.Core.Unit>)'.'

[Tarmil]

This is fixed in Bolero 0.15.23 / Bolero.HotReload 0.15.4. Thanks everyone for the report, investigation and PR!

[naartjie]

Cool @davedawkins, I’m glad that works on Windows too.

I had a go at a PR in #181, but not sure that’s all that’s needed to fix the dependency.

Also with hot reloading, not sure what is broken there. Maybe someone else reading this knows what’s up there.