Cannot open any project in FSharp.sln anymore

[abelbraaksma]

After a fresh update to latest in main and a git clean -xdf, running build.cmd in the root (no errors), trying to open FSharp.sln in Visual Studio 2019 16.7.4 (latest RTM), none of the projects load.

The output window for "solution" shows this log:

D:\Projects\OpenSource\FSharp\src\fsharp\FSharp.Compiler.Server.Shared\FSharp.Compiler.Server.Shared.fsproj : error  : The project file cannot be opened. Unable to locate the .NET Core SDK. Check that it is installed and that the version specified in global.json (if any) matches the installed version.
D:\Projects\OpenSource\FSharp\src\fsharp\fsc\fsc.fsproj : error  : The project file cannot be opened. Unable to locate the .NET Core SDK. Check that it is installed and that the version specified in global.json (if any) matches the installed version.
D:\Projects\OpenSource\FSharp\src\fsharp\FSharp.Compiler.Interactive.Settings\FSharp.Compiler.Interactive.Settings.fsproj : error  : The project file cannot be opened. Unable to locate the .NET Core SDK. Check that it is installed and that the version specified in global.json (if any) matches the installed version.
D:\Projects\OpenSource\FSharp\src\fsharp\fsi\fsi.fsproj : error  : The project file cannot be opened. Unable to locate the .NET Core SDK. Check that it is installed and that the version specified in global.json (if any) matches the installed version.
D:\Projects\OpenSource\FSharp\src\fsharp\fsiAnyCpu\fsiAnyCpu.fsproj : error  : The project file cannot be opened. Unable to locate the .NET Core SDK. Check that it is installed and that the version specified in global.json (if any) matches the installed version.
D:\Projects\OpenSource\FSharp\tests\FSharp.Test.Utilities\FSharp.Test.Utilities.fsproj : error  : The project file cannot be opened. Unable to locate the .NET Core SDK. Check that it is installed and that the version specified in global.json (if any) matches the installed version.
D:\Projects\OpenSource\FSharp\tests\fsharp\FSharpSuite.Tests.fsproj : error  : The project file cannot be opened. Unable to locate the .NET Core SDK. Check that it is installed and that the version specified in global.json (if any) matches the installed version.
D:\Projects\OpenSource\FSharp\tests\FSharp.Compiler.UnitTests\FSharp.Compiler.UnitTests.fsproj : error  : The project file cannot be opened. Unable to locate the .NET Core SDK. Check that it is installed and that the version specified in global.json (if any) matches the installed version.
D:\Projects\OpenSource\FSharp\tests\FSharp.Core.UnitTests\FSharp.Core.UnitTests.fsproj : error  : The project file cannot be opened. Unable to locate the .NET Core SDK. Check that it is installed and that the version specified in global.json (if any) matches the installed version.
D:\Projects\OpenSource\FSharp\src\fsharp\FSharp.Compiler.Private\FSharp.Compiler.Private.fsproj : error  : The project file cannot be opened. Unable to locate the .NET Core SDK. Check that it is installed and that the version specified in global.json (if any) matches the installed version.
D:\Projects\OpenSource\FSharp\src\fsharp\FSharp.Build\FSharp.Build.fsproj : error  : The project file cannot be opened. Unable to locate the .NET Core SDK. Check that it is installed and that the version specified in global.json (if any) matches the installed version.
D:\Projects\OpenSource\FSharp\src\fsharp\FSharp.Core\FSharp.Core.fsproj : error  : The project file cannot be opened. Unable to locate the .NET Core SDK. Check that it is installed and that the version specified in global.json (if any) matches the installed version.
D:\Projects\OpenSource\FSharp\tests\FSharp.Build.UnitTests\FSharp.Build.UnitTests.fsproj : error  : The project file cannot be opened. Unable to locate the .NET Core SDK. Check that it is installed and that the version specified in global.json (if any) matches the installed version.
D:\Projects\OpenSource\FSharp\src\fsharp\Microsoft.FSharp.Compiler\Microsoft.FSharp.Compiler.csproj : error  : The project file cannot be opened. Unable to locate the .NET Core SDK. Check that it is installed and that the version specified in global.json (if any) matches the installed version.
D:\Projects\OpenSource\FSharp\src\fsharp\FSharp.DependencyManager.Nuget\FSharp.DependencyManager.Nuget.fsproj : error  : The project file cannot be opened. Unable to locate the .NET Core SDK. Check that it is installed and that the version specified in global.json (if any) matches the installed version.
D:\Projects\OpenSource\FSharp\src\fsharp\FSharp.Compiler.Private.Scripting\FSharp.Compiler.Private.Scripting.fsproj : error  : The project file cannot be opened. Unable to locate the .NET Core SDK. Check that it is installed and that the version specified in global.json (if any) matches the installed version.
D:\Projects\OpenSource\FSharp\tests\FSharp.Compiler.Private.Scripting.UnitTests\FSharp.Compiler.Private.Scripting.UnitTests.fsproj : error  : The project file cannot be opened. Unable to locate the .NET Core SDK. Check that it is installed and that the version specified in global.json (if any) matches the installed version.
D:\Projects\OpenSource\FSharp\src\fsharp\Microsoft.DotNet.DependencyManager\Microsoft.DotNet.DependencyManager.fsproj : error  : The project file cannot be opened. Unable to locate the .NET Core SDK. Check that it is installed and that the version specified in global.json (if any) matches the installed version.
D:\Projects\OpenSource\FSharp\tests\FSharp.Compiler.ComponentTests\FSharp.Compiler.ComponentTests.fsproj : error  : The project file cannot be opened. Unable to locate the .NET Core SDK. Check that it is installed and that the version specified in global.json (if any) matches the installed version.
D:\Projects\OpenSource\FSharp\tests\fsharpqa\testenv\src\PEVerify\PEVerify.csproj : error  : The project file cannot be opened. Unable to locate the .NET Core SDK. Check that it is installed and that the version specified in global.json (if any) matches the installed version.
D:\Projects\OpenSource\FSharp\tests\FSharp.Compiler.Service.Tests\FSharp.Compiler.Service.Tests.fsproj : error  : The project file cannot be opened. Unable to locate the .NET Core SDK. Check that it is installed and that the version specified in global.json (if any) matches the installed version.
D:\Projects\OpenSource\FSharp\src\fsharp\FSharp.Compiler.Service\FSharp.Compiler.Service.fsproj : error  : The project file cannot be opened. Unable to locate the .NET Core SDK. Check that it is installed and that the version specified in global.json (if any) matches the installed version.

Note that I do have latest VS RTM and latest VS Preview installed. Loading the prj in Preview works, but compiling fails with dozens of these lines:

C:\Program Files\dotnet\sdk\5.0.100-rc.1.20452.10\Sdks\Microsoft.NET.Sdk\targets\Microsoft.NET.Sdk.DefaultItems.targets(349,5): error NETSDK1141: Unable to resolve the .NET SDK version as specified in the global.json located at D:\Projects\OpenSource\FSharp\global.json.

[abelbraaksma]

Ok, looking at the history of global.json this doesn't appear to be something new. The causes:

• After you install a new version by clicking "Update" in the VS installer, older SDK's are uninstalled (see Updating VS 2019 from 16.3.x to 16.4.0 uninstall existing .NET Core SDK 3.0.100 sdk#4015)
• global.json cannot be configured to use the locally installed sdk in the .dotnet directory, which is used when running build.cmd. An issue addressing this has been open since 2017: Add path to global.json SDK version lock sdk#8254
• Apparently we cannot simply stick to a "major" version, see discussion in Allow more SDK versions #10130

Meanwhile, the version was

• upgraded to 401 (4884738#diff-274660eb4b1b1d963a330b471e10f41c),
• then downgraded to 302 (back off sdk version #10051),
• then upgraded again to 401 (Go back to an SDK that is actually installed on machines #10076)
• then downgraded again to 302 (eef171f#diff-274660eb4b1b1d963a330b471e10f41c), which was two weeks ago.
• the latest attempt was to use a more general version, which was canceled (Allow more SDK versions #10130)

If I didn't know any better I'd say there's an editor war going on ;).

It's rather painful that this blocks using the VisualFSharp.sln and the FSharp.sln and others out-of-the box, and as @auduchinok mentioned, disallows building with dotnet build. I'll try with DOTNET_MSBUILD_SDK_RESOLVER_SDKS_DIR, as mentioned here, see if that helps and whether I can set it just before launching VS so as not to disrupt other projects.

PS: this also goes against the instructions in the CONTRIBUTORS.md, which suggests installing latest VS is the recommended way to open the solutions.

[abelbraaksma]

At least for Visual Studio, the following appears to work as a workaround for the time being (or, just re-install the SDK after you update VS):

set DOTNET_MSBUILD_SDK_RESOLVER_CLI_DIR=D:\Projects\OpenSource\FSharp\.dotnet

Or, more generally (assuming you have run build.cmd at least once):

1. Open a command prompt (no need to be an admin prompt or dev prompt) and go to the root dir of the repo
2. Set the environment variable: set DOTNET_MSBUILD_SDK_RESOLVER_CLI_DIR=%CD%\.dotnet
3. Start Visual Studio from that command prompt: start VisualFSharp.sln (this will open Preview if you have it)

Now it should work as it used to, Visual Studio will use the SDK from the environment variable. We could perhaps add a launch.bat that does this automatically so that we don't have to worry about the DotNet SDK's anymore.

For kicks, here's a way to create a Windows shortcut that sets this environment variable and launches VS:

1. Use an existing shortcut or create a new one, go to prop

2. In the target field, assuming 2019 Preview, type (adjust paths accordingly, use ^" to escape a quote, don't forget the final quote, more info here):

   C:\Windows\System32\cmd.exe /c "SET DOTNET_MSBUILD_SDK_RESOLVER_CLI_DIR=D:\Projects\OpenSource\FSharp\.dotnet && start /D ^"C:\Program Files (x86)\Microsoft Visual Studio\2019\Preview\Common7\IDE^" devenv.exe"
   

3. Save and click to start VS, you should see a short flash cmd window and then VS starting (select "start minimized" to get rid of that). The "recent files" on top of the shortcut in the taskbar won't work anymore with this approach, though.

EDIT: apparently that doesn't work, though I don't know why, the env vars are visible in Process Explorer. Back to good ol' batch files, this works:

set DOTNET_MSBUILD_SDK_RESOLVER_CLI_DIR=D:\Projects\OpenSource\FSharp\.dotnet
start %1

Call it like launch fsharp.sln.

[cartermp]

Closing this out since I can open all the solutions in our repo with VS currently