[Docs] MSBuild task missing info on workaround regarding duplicate AssemblyVersionAttributes in WPF projects

[hymccord]

I ran into this problem today but there is already a workaround in place with the .NET Core 5.0.200 SDK.
Prereqs:

• SDK styled project using WPF
• Targeting net5.0-windows (I didn't test others)
• .NET Core 5.0.200 SDK (or lower to produce the error)

Minimal repro:
net5wpf_gitversionbug.zip
or make the repro yourself

dotnet new wpflib -f net5.0 -o wpfbug
cd wpfbug
dotnet new gitignore
dotnet new globaljson --sdk-version 5.0.200
dotnet add wpfbug.csproj package gitversion.msbuild
git init && git add -A && git commit -m Init
# You'll need to add a usercontrol to the project (via visual studio) so it'll do a two-compile pass
dotnet build

You should get a few errors regarding duplicate attributes. WPF temporary projects don't properly import package reference props and targets. This leads to the temporary project making it's own AssemblyInfo.cs file it thinks it hasn't been generated yet.
In actuality, a second one is then generated and CSC picks up both during the CoreCompile target of the temp assembly... leading to this!

 C:\Users\Hank\source\repos\wpfbug\obj\Debug\net5.0-windows\wpfbug_r4a111wm_wpftmp.AssemblyInfo.cs(15,12): error CS0579: Duplicate 'System.Reflection.AssemblyFileVersionAttribute' attribute [C:\Users\Hank\source\repos\wpfbug\wpfbug_r4a111wm_wpftmp.csproj]
C:\Users\Hank\source\repos\wpfbug\obj\Debug\net5.0-windows\wpfbug_r4a111wm_wpftmp.AssemblyInfo.cs(16,12): error CS0579: Duplicate 'System.Reflection.AssemblyInformationalVersionAttribute' attribute [C:\Users\Hank\source\repos\wpfbug\wpfbug_r4a111wm_wpftmp.csproj]
C:\Users\Hank\source\repos\wpfbug\obj\Debug\net5.0-windows\wpfbug_r4a111wm_wpftmp.AssemblyInfo.cs(19,12): error CS0579: Duplicate 'System.Reflection.AssemblyVersionAttribute' attribute [C:\Users\Hank\source\repos\wpfbug\wpfbug_r4a111wm_wpftmp.csproj]

If you specify a new property (IncludePackageReferencesDuringMarkupCompliation) that was put in in the 5.0.200 release, you can build successfully.
dotnet build -p:IncludePackageReferencesDuringMarkupCompilation=true

I hope this seems appropriate to file an issue here.

Is the best place to put this info in ~docs/input/docs/usage/msbuild.md? If so, I can contribute and submit a PR to help guide people if they run into this error as that flag is not well documented.
If it's of no concern to gitversion, I can close the issue 😄

It should go away with .NET6 as the flag will be enabled by default.

Thanks!

[stale]

This issue has been automatically marked as stale because it has not had recent activity. After 30 days from now, it will be closed if no further activity occurs. Thank you for your contributions.

[MindaugasLaganeckas]

@inkahootz : the issue is relevant. It is a bit disappointing, that no one from the project would look into it.

[asbjornu]

Sorry for not responding until now. I think @inkahootz' proposal of adding information to the documentation is a good one and would accept a PR for that.

[asbjornu]

However, please see #2841 that already added some related information. A PR expanding on that should take the existing information into account.

[hymccord]

I will investigate the interaction between the GenerateAssemblyXAttribute flags and the IncludePackageReferencesDuringMarkupCompliation flag and submit a PR if appropriate.

I do feel there is some room for documentation since net5.0 is still the current release, so there will probably be a PR.

[hymccord]

@asbjornu LMK if I need to trim off the last commit and open a separate issue for that.

I did my best to verify that the change works back to .NET Core 3.1 with resource URI's showing the correct version.

Thanks for reopening the issue by the way! Just glad we can get it fixed 👍