Setting DOTNET_HOST_PATH is not a good move :)

[dsyme]

ProjInfo sets DOTNET_HOST_PATH to an invalid value (the name of the currently executing program) when being run inside a .NET tool (e.g. fsdocs.exe rather than dotnet.exe) here

proj-info/src/Ionide.ProjInfo/Library.fs

Line 168 in 6a6bdf3

match System.Environment.GetEnvironmentVariable "DOTNET_HOST_PATH" with

This is because the default logic for dotnetPath assumes the current process is dotnet.exe but for a tool host like fsdocs.exe it isn't run by dotnet.exe, e.g.

proj-info/src/Ionide.ProjInfo/Utils.fs

Line 39 in 6a6bdf3

System

In any case, the setting of DOTNET_HOST_PATH should be strongly protected by a try/finally? If used at all?

(Setting DOTNET_HOST_PATH to an invalid value confuses the heck out of FSharp.Compiler.Service.dll )

[baronfel]

I think DOTNET_HOST_PATH was required for some msbuild targets/props/shenanigans, so we should require it in some way, but I agree with you that the last-chance fallback of the app name isn't suitable for cases where the caller is in an AppHost and not the dotnet host. I think we can remove that last-chance and raise an exception in the init function if that's the case. That will require callers to set at least one of the valid detection variables, though, which ideally would be represented as an input to the function somehow...

[baronfel]

One hurdle here is that the .NET SDK doesn't forward any of the environment variables we look for on to local or global tools, like it does for other commands. It might be good to advocate for that feature, because as it stands, tools have no consistent way to detect the dotnet installation that's running them.

[baronfel]

Talking with some of the SDK team, the DOTNET_ROOT variable is only set if the install location isn't one of the well-known ones. So we should do probing if there's no DOTNET_ROOT.

[baronfel]

The final algorithm should look something like:

• DOTNET_HOST_PATH
• DOTNET_ROOT/DOTNET_ROOT(x86)
• probe PATH
• probe default install locations per-OS
• fail hard if none found

[baronfel]

@dsyme this was released in 0.55.1

[baronfel]

@dsyme ok, 0.55.2 has a more sane strategy that doesn't touch DOTNET_HOST_PATH