[Guava] Multi-target for .NET 6 and MonoAndroid90

[jonathanpeppers]

So far ported these packages to .NET 6:

• Xamarin.Google.Guava
• Xamarin.Google.Guava.FailureAccess
• Xamarin.Google.Guava.ListenableFuture

This requires:

• Xamarin.Android from VS 16.10
• .NET 6.0.100-preview.4.21255.9
• .NET 6 Android workload
• Xamarin.Legacy.Sdk
• Updated build.cake to use dotnet build

[jonathanpeppers]

This sample isn't really that helpful, basically just an "integration test" checking a type exists.

When I look at GuavaSample.dll it has the same .jar files embedded as before:

[jpobst]

Package looks the same, other than MonoAndroid50 -> MonoAndroid90, which I assume is intended.

You will likely want to bump the patch version numbers so they are higher than the ones currently published on NuGet?

[jpobst]

Unrelated question, we specify net6.0-android:

<TargetFrameworks>net6.0-android;monoandroid90</TargetFrameworks>

The TF in the NuGet is net6.0-android30.0. Is that expected?

[jonathanpeppers]

I didn't change any of the monoandroid90 values, they seem the same as before?

If you leave the 30 off of net6.0-android, it will use a value from a generated .targets file:

https://github.com/xamarin/xamarin-android/blob/b36df8fbeb15bcc2bcbe239d7ce49f8ec93ad263/build-tools/Xamarin.Android.Tools.BootstrapTasks/Xamarin.Android.Tools.BootstrapTasks/GenerateSupportedPlatforms.cs#L63-L65

Such as:

<TargetPlatformVersion Condition=" '$(TargetPlatformVersion)' == '' ">30.0</TargetPlatformVersion>

We could explicitly put 30 here? It will change to 31 by default at some point.

[jpobst]

Maybe feels safer to explicitly use 30? It seems without it we run the risk of updating our XA at some point and accidentally releasing new packages that don't work for existing users.

[moljac]

LGTM