LGTM. Is anyone using $(env.) or $(sys.)? I assume we can just add them later if it comes up.

Yeah, this case is interesting:

  <?define Platform   =   "$(sys.BUILDARCH)" ?>

What should sys.BUILDARCH evaluate to?

Platform should already be set in DefineConstants, as I see it in aspnetcore and sdk builds, so this is likely not needed.

LGTM, other than maybe we should pull the preprocessor stuff out into a different file? Wouldn't block on that though.

To @joeloff's question, I know at least aspnetcore does not use $(env.) or $(sys.)

At first I considered moving preprocessor code to a different file. But, it later became intertwined with the task as it needs to call some of the methods, i.e. to ingest variables.

LGTM. Is anyone using $(env.) or $(sys.)? I assume we can just add them later if it comes up.

Yeah, this case is interesting:

arcade/src/Microsoft.DotNet.Build.Tasks.Installers/build/wix/variables.wxi

Line 16 in 0a1768a

<?define Platform = "$(sys.BUILDARCH)" ?>

  <?define Platform   =   "$(sys.BUILDARCH)" ?>

What should sys.BUILDARCH evaluate to?

Platform should already be set in DefineConstants, as I see it in aspnetcore and sdk builds, so this is likely not needed.

So, this seems to be set by Wix toolset to the value of InstallerPlatform, which is already defined in DefineConstants. I can add this rather easily.

I've added support for known system variables that are used in .NET authoring - 18f3f76

We can add more later, but this is enough for all .NET installers at the moment.

@joeloff @wtgodbe