Ionide-vscode-fsharp: FSAC error message. Must add a reference to assembly 'netstandard'

[IvanAntipov]

Describe the bug
Unexpected FSAC error

To Reproduce

1. Add Python.Runtime.NETStandard package to Paket
2. Create Repro\test.fsx file with content

#load @"../.paket\load\net472\Python.Runtime.NETStandard.fsx"
#r "netstandard"

open System
open Python.Runtime

let gil = Py.GIL()

1. See error
   FSAC Message
   >> The type 'Object' is required here and is unavailable. You must add a reference to assembly 'netstandard, Version=2.0.0.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51'.F# Compiler(1108)

Expected behaviour
No error

Screenshots

Environment (please complete the following information):

• OS: Windows 10
• Ionide version: 4.0.6
• VSCode version: 1.38.0
• dotnet SDK version: .NET Core SDK (3.0.100-preview9-014004)
• mono / .Net Framework version: F# Interactive version 10.5.0.0 for F# 4.6

Additional context

There is no error during script execution, FSAC error only

Knows Workaround

Add

#r "facades/netstandard"

This fix FSAC, but break interactive

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[JanWosnitza]

Can confirm. Also happens to me only with newly released version 4.1.0.

For me version 4.0.6 still works. (select "Install another version...")

If it's a different bug, I can open a new issue :)

[baronfel]

This is probably to do with how we resolve 'project options' and references for scripts. Right now this does not handle .net core scenarios well at all, and work needs to be done in FSAutoComplete/dotnet-proj-info to provide a more complete set of those references.

In the meantime there should be a workaround: provide a path to a known-good netstandard.dll.

There are a few places this can be found:

• if you're running on .net core, you can find netstandard.dll in <dotnet sdk root>/shared/Microsoft.NETCore.App/<dotnet sdk version>/netstandard.dll
• if you're not, you can try adding a package reference to the Netstandard.Library package and adding a reference to the netstandard.dll found in <nuget cache root>/packages/netstandard.library/2.0.3/build/netstandard2.0/ref/netstandard.dll

Either one of those should correct your experience, and in fact a lot of the work we have to do is in automatically locating those and adding the correct ones for you.

[nhirschey]

I added #r @"C:\Program Files\dotnet\shared\Microsoft.NETCore.App\2.2.7\netstandard.dll" at the top of my script. I still see lots of issues like "type string is not defined" when defining a record.

FYI, I know lots of work here and I appreciate it all.

To clarify further: I'm on ionide 4.1, using netcore fsac. It worked before upgrading (I'd spent much of Monday figuring out how to get my setup working again after a prior update changed things).

[CaptnCodr]

It's not only .fsx I upgraded today to Ionide 4.1.0 and my .fs files are full of errors, too.
Build with dotnet build: everything's fine. But the linter is saying I have to add 'netstandard' to my references.

[alfert]

I have the same issue as @CapnCodr, interestingly only in one .fs file of my project.

[alfert]

A workaround for a regular project if working with paket: add NETStandard.Library to the references in paket.references. It is like the linter said, but I did not grasp what to do until a few minutes ago ...

[KingKnecht]

Adding the paket NETStandard.Library doesn't solve the problem for me.

[Krzysztof-Cieslak]

We're tracking problems with .fsx files in #1220