There is no warning / error when PublishAot is true, but compiler is not restored

[nohwnd]

Describe the bug

I have a project that we want to build with and without NativeAot. I've published it locally for NativeAot by setting /p:PublishAot=true and everything is correctly compiled to native code.

I push the same command to server and there it compiles without a warning, but it is not NativeAot. All my tests pass, and I only noticed this because I was looking specifically for trim warnings, and was checking and printing: Console.WriteLine("Dynamic code supported: " + System.Runtime.CompilerServices.RuntimeFeature.IsDynamicCodeSupported);

The problem is that locally I have IlcCompiler in my global nuget cache, but on server there is none. Which makes this condition fail:

NoImport: $(ILCompilerTargetsPath) at (1238;3) false condition; 
('$(ILCompilerTargetsPath)' != '' and '$(PublishAot)' == 'true' was evaluated as '' != '' and 'true' == 'true').

I think this is an easy mistake to make. Would it make sense to get an error when PublishAot = true, but the build result would not be NativeAot?

To Reproduce

Have a project targetting net8.0, have .nuget cache populated from previous experimentations with nativeaot.

ILCompilerTargetsPath = C:\Users\me.nuget\packages\microsoft.dotnet.ilcompiler\8.0.0-preview.5.23280.8\build\Microsoft.DotNet.ILCompiler.SingleEntry.targets

Publish the project locally and get native aot exe.

Publish the project on build server and get non-native exe.

Exceptions (if any)

Further technical details

I am on dotnet 8.0.100-preview.5.23303.2, I have binlogs, but they are for internal project so I will have to share them using a differnet channel.

Related to #30091 ?

[vitek-karas]

@sbomer could you please take a look? This should definitely NOT happen.

[nohwnd]

Thanks Vitek, I've shared the details with Sven.

[nohwnd]

I've found the causes of the issue:

1. I was not restoring the Microsoft.Dotnet.ILCompiler package, which results in NoImport of the native aot targets.
2. We are not using the global packages cache, and instead specify a local path in nuget.config, so we can have x copies of our repository locally and don't clash our own built packages in the global cache. Build does not detect this and searches for the presence of Microsoft.Dotnet.ILCompiler in the global nuget cache, where it won't find it. Again not importing the native aot targets.

NoImport:

$(NuGetPackageRoot)\microsoft.dotnet.ilcompiler\8.0.0-preview.5.23280.8\build\Microsoft.DotNet.ILCompiler.props 
at (28;5) false condition; 
(Exists('$(NuGetPackageRoot)\microsoft.dotnet.ilcompiler\8.0.0-preview.5.23280.8\build\Microsoft.DotNet.ILCompiler.props') 
was evaluated as 
Exists('C:\Users\serverrunner\.nuget\packages\\microsoft.dotnet.ilcompiler\8.0.0-preview.5.23280.8\build\Microsoft.DotNet.ILCompiler.props')).

My package cache is not at C:\Users\serverrunner\.nuget\packages, instead it is in the place that I specify in nuget.config. This value looks to be correctly picked up by NugetPackageFolders variable but not by NugetPackageRoot property.

Specifying the /p:NuGetPackageRoot explicitly make it trigger native aot build.