Fsharp: Go To Definition fails if containing file is referenced with forward slash

[chadunit]

__UPDATE: Issue with forward slashes, not junctions.__

See https://github.com/Microsoft/visualfsharp/issues/4016#issuecomment-348663946.

Go To Definition fails for a symbol if the containing file is in a directory that is linked via NTFS junction or symbolic link.

Go To Definition fails for a symbol if the containing file is in a directory that is referenced with forward slashes in the .fsproj file.

In a .NET Standard F# project, this fails with error "Cannot navigate to the symbol under the caret."

In a .NET Framework F# project, this works.

In a .NET Standard C# project, this works.

Repro steps

In Visual Studio, create a __Class Library (.NET Standard)__ F# project.

Create a .fs file in a subdir.

Create a junction to the subdir. (e.g. in Powershell run: New-Item myjunction -ItemType Junction -Value origsubdir)

Edit your .fsproj and manually reference the file using a forward slash.

In your main Library.fs, reference something from that file and then try to F12 to it. Results in error: "Cannot navigate to the symbol under the caret."

(Note that intellisense/compilation are working; just F12 fails.)

Related information

Visual Studio Community 2017 Preview
Version 15.5.0 Preview 4.0
Visual F# Tools (Experimental) 15.4.1.17112401 (from feed: https://dotnet.myget.org/F/fsharp-preview/vsix)
dotnet 2.1.1-preview-007165

[chadunit]

Update:

This is not an issue with junctions. It is an issue with forward slash path separators in the project file. (In trying to create a minimal repro I had hand-edited the fsproj and used forward slashes without realizing that could be the issue.) However it is still true that only .NET Standard F# fails with forward slashes; I verified with hand-edited F# "classic" and C# projects that they worked with forward slashes.

The navigation failure essentially stems from here:

https://github.com/Microsoft/visualfsharp/blob/afb8b75ae9523f69d20b7f853c0c8d939ddd089d/src/fsharp/NameResolution.fs#L1463

The equality fails because one side has forward slashes and the other backslashes.

The root cause seems to be here:

https://github.com/Microsoft/visualfsharp/blob/afb8b75ae9523f69d20b7f853c0c8d939ddd089d/vsintegration/src/FSharp.Editor/LanguageService/LanguageService.fs#L229-L233

The sources coming in retain the forward slashes verbatim from the project file.

Would the following fix for the above nested function be suitable? Using Path.GetFullPath (which uses winapi GetFullPathNameW) to convert to a canonical form with backslashes.

let fullPath p =
    if Path.IsPathRooted(p) then p
    else Path.Combine(Path.GetDirectoryName(path), p)
    |> Path.GetFullPathSafe

[cartermp]

@chadunit I think that's a good thing to try. @KevinRansom for FYI as he implemented this.

[piaste]

Oh woah, thanks a lot for figuring this out! I'd been using forward slashes to avoid any potential issues with the Linux build server, and I had just assumed F12 was still buggy.

[uncleyo]

This is still the problem with latest versions of VS 2017 and 2019 Preview.
In addition to "Go To Definition", it reversely affects "Find All References".

And dotnet new ... F# template for ASP.NET Core inserts forward slash in fsproj.

I'd gladly try to create a PR, but given the fix is already suggested, that feels like stealing credit 🙂