[.NET Framework Projects] IDE is confused about the last file to compile

[majocha]

Current master

It builds and runs OK. The false error is only in the IDE.

Repro:

Create a solution with two or more console app projects.

[vasily-kirichenko]

.net core? this is expected

[majocha]

Not dotnet core, .Net Framework 4.6.1
I've noticed this in Gjallarhorn WPF sample projects at first.

[dsyme]

@KevinRansom @cartermp Something is quite busted on master, I think it is to do with cases where source files in projects get interpreted as if they are single file projects

[majocha]

@KevinRansom I think I have some idea what's going on.

https://github.com/Microsoft/visualfsharp/blob/6c6de72d154a550732dd1ce818f64ad75fee843c/vsintegration/src/FSharp.Editor/LanguageService/LanguageService.fs#L414-L417

This event with ProjectAdded args fires during solution load, and it can fire well before SetupProjectFile or SyncProject had a chance to run for a given project. Execution goes here https://github.com/Microsoft/visualfsharp/blob/6c6de72d154a550732dd1ce818f64ad75fee843c/vsintegration/src/FSharp.Editor/LanguageService/LanguageService.fs#L163-L170
and, I guess, things break because InvalidateConfiguration is being called for a project that is not set up?

Commenting out this line
https://github.com/Microsoft/visualfsharp/blob/6c6de72d154a550732dd1ce818f64ad75fee843c/vsintegration/src/FSharp.Editor/LanguageService/LanguageService.fs#L416

fixes this issue and the other one (#3545) but I'm not sure what it breaks in return. I don't fully understand why it is needed.

[dsyme]

and, I guess, things break because InvalidateConfiguration is being called for a project that is not set up?

Yes, that sounds like the problem

AFAIK the line is only needed for new-style .NET SDK project files (where a Roslyn project already exists). SetupProjectFile is needed for old-style project files. We need to somehow do the right thing here for old-style projects

[KevinRansom]

Hmmm looks like I broke something. On it.

[cartermp]

cc @Pilchie for FYI

[dsyme]

Fixed by #3603 - thanks for resolving this @KevinRansom