Cannot use locally built F# compiler within VS

When building F# project using custom build F# compiler with custom keywords from Visual Studio error happens

FSC error FS2020: The assembly 'C:\d\github\dotnet\fsharp\artifacts/bin/fsc/Debug/net7.0/fsc.dll' is listed on the command line. Assemblies should be referenced using a command line flag such as '-r'. [C:\d\github\funsharp\ісх\ВеселШарп.Бібліотека.fsproj]

Even if build in VS does not works, what working

• Build using dotnet build
• Colorization within VS. New keywords correctly highlighted.

Repro steps

1. Clone F# repo to C:\d\github\dotnet\fsharp
2. Add aliases to existing F# keywords, For example add let => leet
3. Create project which use these custom keywords.
4. Add following properties in the Directory.Build.props of the F# project

<PropertyGroup>
  <FSharpRoot>C:\d\github\dotnet\fsharp\</FSharpRoot>
  <DotnetFscCompilerPath>$(FSharpRoot)artifacts/bin/fsc/Debug/net7.0/fsc.dll</DotnetFscCompilerPath>
  <Fsc_DotNET_DotnetFscCompilerPath>$(FSharpRoot)artifacts/bin/fsc/Debug/net7.0/fsc.dll</Fsc_DotNET_DotnetFscCompilerPath>
   <!-- these experiments and probably do not affect anything -->
  <FSharpPreferNetFrameworkTools>false</FSharpPreferNetFrameworkTools>
  <FSharpCompilerPath>$(FSharpRoot)artifacts/bin/fsc/Debug/net7.0/</FSharpCompilerPath>
</PropertyGroup>

1. Open VisualFSharp.sln
2. Run VisualFSharpDebug project
3. Open F# project with custom keywords.
4. Build project in the VS

In case if this is needed.

• Custom F# compiler https://github.com/kant2002/fsharp
• Test F# solution which used custom keywords https://github.com/kant2002/funsharp/tree/головна-фшарп

** Investigation ** From what I see DotnetFscCompilerPath passed to the Fsc task. And then FSC task produces

C:\d\github\dotnet\fsharp\artifacts\bin\fsc\Debug\net7.0\fsc.exe C:\d\github\dotnet\fsharp\artifacts/bin/fsc/Debug/net7.0/fsc.dll -o:obj\Debug\net7.0\ВеселШарп.Бібліотека.dll
-g
...
skipped
...

My understanding that proper call should be

dotnet.exe C:\d\github\dotnet\fsharp\artifacts/bin/fsc/Debug/net7.0/fsc.dll -o:obj\Debug\net7.0\ВеселШарп.Бібліотека.dll
-g
...
skipped
...

binlog.zip

[KevinRansom]

@kant2002 – okay I believe I have a much better 1 property solution. https://github.com/dotnet/fsharp/pull/14422

Once the PR is merged you will be able to do this:

  <PropertyGroup>
    <FSharpCompilerPath>C:\kevinransom\fsharp\artifacts\bin\fsc\Debug\net7.0\fsc.exe</FSharpCompilerPath>
  <PropertyGroup>

[vzarytovskii]

The following works for me in both VS and CLI:

<PropertyGroup>
  <DisableAutoSetFscCompilerPath>false</DisableAutoSetFscCompilerPath>
  <DotnetFscCompilerPath>$(MSBuildThisFileDirectory)../../../artifacts/bin/fsc/Debug/net7.0/fsc.dll</DotnetFscCompilerPath>
  <FSharpPreferNetFrameworkTools>False</FSharpPreferNetFrameworkTools>
  <FSharpPrefer64BitTools>True</FSharpPrefer64BitTools>
</PropertyGroup>

It may fail to work if shipped runtime in VS is a lower version than the compiler tfm.