Custom project types support is broken in slnx

[ernestasju]

Hi,

While I was playing with custom project types, I found this bug. I made a minimal repro: repro.zip.

P.S. You can ignore this rant.

Can Microsoft Business Central AL guys and MSBuild guys meet somehow? Please, it is getting ridiculous - AL side is reinvented the wheel and all multiple times already (ALOPS, NAVERTICAL, ALPACA, AL-GO, us, the list goes on) and we still don't have decent solution compilation like there is in dotnet - just a bunch of powershell scripts and still no package manager/repository after like 6+ years since the inception of AL.

This description was generated by AI.

.slnx vs .sln: Custom Project Type Build Behavior

Repro Steps

1. Place these files in the same folder:

   • A.sln
   • A.slnx
   • A.alproj
   • AL.Build.targets

2. Run the following commands from the folder:

   dotnet build A.sln
   dotnet build A.slnx
   

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Output

dotnet build A.sln

Good. It actually runs the al.exe.

Restore succeeded with 2 warning(s) in 0,0s
    C:\Users\ernes\Desktop\bad publish repro\Product\repro\A.alproj : warning NU1503: Skipping restore for project 'C:\Users\ernes\Desktop\bad publish repro\Product\repro\A.alproj'. The project file may be invalid or missing targets required for restore. C:\Program Files\dotnet\sdk\10.0.102\NuGet.targets(196,5): warning Unable to find a project to restore!
A failed with 2 error(s) (0,1s)
    EXEC : error AL1001: Source file 'C:\Users\ernes\Desktop\bad publish repro\Product\repro\app.json' could not be found
    C:\Users\ernes\Desktop\bad publish repro\Product\repro\AL.Build.targets(5,5): error MSB3073: The command "al.exe compile /project:"C:\Users\ernes\Desktop\bad publish repro\Product\repro" /out:"C:\Users\ernes\Desktop\bad publish repro\Product\repro\.output\A.app" /packagecachepath:"C:\Users\ernes\Desktop\bad publish repro\Product\repro\..\.alpackages"" exited with code 1.
Build failed with 2 error(s) and 2 warning(s) in 0,3s

dotnet build A.slnx

Bad. It fails to recognize project type.

A.slnx(2,4): error MSB4025:
  The project file could not be loaded. Microsoft.VisualStudio.SolutionPersistence.Model.SolutionException: ProjectType '' not found. (Parameter 'projectTypeName')
  ...
Build failed with 1 error(s) in 0,0s

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Summary

• .sln builds and runs the custom AL project, but fails due to missing app.json (expected for repro).
• .slnx fails with ProjectType '' not found, even with minimal or custom ProjectTypeDefinition attempts.
• This demonstrates a gap in .slnx support for custom project types (like .alproj) in the .NET SDK.