Fixed: WPF workaround for importing extensions does not always work

[ivan-danilov]

The issue happens when BaseIntermediateOutputPath is overridden, thus
MSBuildProjectExtensionsPath gets assigned without generated suffix
even in *_wpftmp.*proj file.
Since _SdkOriginalProjectExtensionsPath didn't have a fallback value -
that prevented importing project extensions. This change adds the
fallback, making it effectively like "if there's a suffix - remove it,
otherwise use as is".

[ivan-danilov]

The error does not seem to be related to my changes. Am I expected to do something with it?

[ivan-danilov]

@clairernovotny any comments on this PR?

[clairernovotny]

Please rebase or bring in master and then I can merge

[clairernovotny]

Question: Have you tried the main .NET Core 3.1 SDK with the WindowsDesktop SDK an UseWpf set to true? Does that work?

Curious as to why you need the extras for WPF currently?

[ivan-danilov]

@clairernovotny it is for 1.6 branch and it is up to date with rel/1.6. master might need the same fix but I don't have a project to check it on, therefore reluctant to make unchecked changes there.

We use .NET Core build process for an old WPF project. For technical reasons the project can't switch to .NET Core completely (binaries must be loadable into .NET Framework process) but using .NET Core build tools allows to use newer NuGet, SDK-style project files with csproj-specified NuGet dependencies (rather than package.config) etc.

[clairernovotny]

I'm not planning on releasing any more 1.6 releases. What's keeping you on that old version?

[ivan-danilov]

@clairernovotny sorry for the delayed response, I had to retry the upgrade. I remember I tried it back in January but completely forgot why decided to stay on the old branch.
I think it is this NETSDK1107 warning.

I'll update to the last version and rebase.

[ivan-danilov]

@clairernovotny I hope you are well and healthy.
Just a kind reminder about this PR :)

I saw some related activity in WPF/NuGet repos but they don't look exactly promising yet.

[ivan-danilov]

Thanks! :)