.NET MAUI size regression

[jonathanpeppers]

.NET MAUI projects regressed in size after:

dotnet/maui@dfc9a20

Before:

After:

It appears the problem is that [assembly: AssemblyMetadata ("IsTrimmable", "True")] is not present in this assembly.

Somehow this line isn't picked up:

https://github.com/xamarin/AndroidX/blob/41f867f3f86e3e57d8f1aad396c29dd24ced2067/source/AssemblyInfo.cs#L13

One solution might be to set $(IsTrimmable) in a Directory.Build.targets instead of doing it in a C# file. That would also get the benefits of some of the trimmer analyzer warnings/errors as well.

[jonathanpeppers]

It appears other assemblies might need the same treatment:

Xamarin.Kotlin.StdLib.Jdk7.dll
Xamarin.Kotlin.StdLib.Jdk8.dll

[eerhardt]

this is the project that brings this new dependency in:

Before:

After:

AndroidX.Fragment.Ktx is the new dependency that brings in all the kotlin stuff

[eerhardt]

Just marking these Kotlin assemblies as "trimmable" reduces the amount of .NET assembly sizes drastically:

  <ItemGroup>
    <TrimmableAssembly Include="Xamarin.Kotlin.StdLib.Common" />
    <TrimmableAssembly Include="Xamarin.Kotlin.StdLib" />
    <TrimmableAssembly Include="Xamarin.Kotlin.StdLib.Jdk7" />
    <TrimmableAssembly Include="Xamarin.Kotlin.StdLib.Jdk8" />
    <TrimmableAssembly Include="Xamarin.KotlinX.Coroutines.Android" />
    <TrimmableAssembly Include="Xamarin.KotlinX.Coroutines.Core.Jvm" />
  </ItemGroup>

produces:

cc @jonpryor

Note, I don't know what Xamarin.Jetbrains.Annotations is, but it feels like we should remove that so we don't have files named "JetBrains" in a Maui app.

[jpobst]

JetBrains is the author of Kotlin, and Kotlin depends on this package:
https://mvnrepository.com/artifact/org.jetbrains/annotations

[eerhardt]

JetBrains is the author of Kotlin, and Kotlin depends on this package:

Are you sure it isn't just needed at development time? Reading this blog about the .NET JetBrains.Annotations package, I see:

As a rule of thumb, it’s usually best to reference the JetBrains.Annotations NuGet package when a project is not intended to be shared outside a development team. The NuGet package uses the [Conditional("JETBRAINS_ANNOTATIONS")] attribute to ensure the annotations are not compiled into the resulting assembly. In other words: it is there while developing and your team can use the annotations, but it’s gone when compiled.

The only package I see that has a dependency on Xamarin.Jetbrains.Annotations is Xamarin.Kotlin.StdLib. And if I look at that assembly in ILSpy, I don't see a reference to Xamarin.Jetbrains.Annotations:

So is this really needed?

Note, if I add Xamarin.Jetbrains.Annotations to the TrimmableAssembly list above, it gets completely trimmed away.

[jpobst]

Note that that is a different JetBrains.Annotations package. That is their package for their .NET annotations. The one we use is our Xamarin.Android .NET bindings of their Java .jar annotations.

The PR for this will add Trimmable to all AndroidX dependencies, so if it is not needed it will be trimmed away as well.