Trimming default WPF app breaks it

[vitek-karas]

dotnet new wpf
dotnet publish -r win-x64 /p:PublishTrimmed=true
run the app

Running the app "does nothing" no window shows up.

Note that this is a regression from 3.1 where this worked.

Used: 5.0.100-rtm.20515.8 SDK

[DavidZidar]

I am looking for guidance on how to publish a WPF app using PublishTrimmed, I am fine with manually adding TrimmerRootAssembly entries to my project but I need to know which ones to add.

[vitek-karas]

This is probably a combination of linker changes (being more precise) and WPF changes.

System.Runtime

It's referenced from code which linker doesn't see, because the module .cctor for PresentationCore contains code like:
Assembly.GetExecutingAssembly().GetType(...).GetMethod(...).Invoke() - linker doesn't recognize this pattern and won't follow it, even though it's fully hardcoded values.

Note that this is injected via ILDASM/ILASM from this file https://github.com/dotnet/wpf/blob/master/eng/WpfArcadeSdk/tools/InjectModuleInitializer/ModuleInitializer.il

System.Runtime.Extensions

It's referenced from the C++/CLI assembly DirectWriterForwarder.
It should probably be added to https://github.com/dotnet/wpf/blob/master/src/Microsoft.DotNet.Wpf/src/PresentationCore/ILLinkTrim.xml

System.Diagnostics.Debug

Again referenced from DirectWriterFormatter
It's already listed in https://github.com/dotnet/wpf/blob/master/src/Microsoft.DotNet.Wpf/src/PresentationCore/ILLinkTrim.xml so either it's not correctly embedded or linker doesn't read it right.

So as a workaround I added:

  <ItemGroup>
    <TrimmerRootAssembly Include="System.Runtime"/>
    <TrimmerRootAssembly Include="System.Runtime.Extensions"/>
    <TrimmerRootAssembly Include="System.Diagnostics.Debug"/>
  </ItemGroup>

To the project and now the empty template app works (checked that there are no exceptions at runtime either).
That doesn't mean that once the app starts actually doing something it won't fail on other assemblies missing.

The size savings are interesting but not amazing. Untrimmed size: 148MB, trimmed size: 91MB.

[jkotas]

Note that this is injected via ILDASM/ILASM from this file

This should be replaced by the proper C# module initializer now that that C# can emit them.

[vitek-karas]

I just tried using the module initializer and it fixes the problem with that part of the code https://github.com/vitek-karas/wpf/tree/UseModuleInit. But it uncovers another problem:

• The module initializer has a direct reference to DirectWriterForwarder which is a C++/CLI assembly
• SDK detects this and doesn't pass the assembly to the linker as one of the inputs, but linker will find it out anyway (probing) and will process it.
• But it seems linker runs it through Cecil (roundtrip) which changes the assembly. It's unclear how much of the assembly actually survives the linking in a working state. The assembly is smaller by about 30KB and looking at it in ILSpy it looks different.

[agocke]

Closing as dup of dotnet/wpf#3811

[vatsan-madhavan]

This should be replaced by the proper C# module initializer now that that C# can emit them.

👍

Replacing this infrastructure is exactly why @rladuca and I pushed for the C# module-initializer feature (along with many others for many other good reasons). This should absolutely be changed in .NET 6. The ILASM/ILDASM trick is ok for now, but it's meta-stable at best.

/cc @SamBent @ryalanms