Blazor WASM apps should fully trim Microsoft.Extensions.* assemblies

[eerhardt]

Today, when publishing a Blazor WASM app, we are telling the ILLinker to trim Microsoft.Extensions.* assemblies, but only at a "type granularity" level. Meaning, if some part of the Type is used, preserve the whole Type.

aspnetcore/src/Razor/Microsoft.NET.Sdk.Razor/src/build/netstandard2.0/Microsoft.NET.Sdk.Razor.Components.Wasm.targets

Lines 372 to 377 in 6c35e2e

	<_BlazorTypeGranularAssembly
	Include="@(ManagedAssemblyToLink)"
	Condition="'%(Extension)' == '.dll' AND ($([System.String]::Copy('%(Filename)').StartsWith('Microsoft.AspNetCore.')) or $([System.String]::Copy('%(Filename)').StartsWith('Microsoft.Extensions.')))">
	<Required>false</Required>
	<Preserve>all</Preserve>
	</_BlazorTypeGranularAssembly>

This causes unnecessary bloat in the produced app because there are types in Microsoft.Extensions.* where some unused code is pulling in more System.* assemblies (e.g. System.Diagnostics.DiagnosticSource.dll), causing even more unused code to be compiled in the app.

With the recent work done in Extensions to make them linker-friendly:

• Annotate DependencyInjection to make it linker friendly runtime#40227
• Annotate Extensions.Options to make it linker friendly runtime#40294
• Make Extensions linker friendly. runtime#40431

we should be able to remove the "type granularity" clauses for these assemblies now that they are linker safe.

Using a recent rc1 build, I'm seeing the following size savings in IL:

	Uncompressed IL	Compressed IL (.br)
master	2,426,368 bytes	852,236 bytes
PR	2,339,328 bytes	822,834 bytes
Difference	87,040 bytes (85 KB)	29,402 bytes (28.7 KB)

cc @SteveSandersonMS @pranavkm @marek-safar

[SteveSandersonMS]

Thanks @eerhardt!

[samsp-msft]

Once complete, does this mean that the Microsoft.AspNetCore.* and Microsoft.Extensions.* assemblies should just get standard TrimMode=Trim behavior?

[eerhardt]

My thinking is that only Microsoft.Extensions.* assemblies will get the standard TrimMode=Trim behavior to start with. We've done the work to ensure they are linker-safe. I don't think anyone has done the work to make all the Microsoft.AspNetCore.* assemblies to be linker-safe. @davidfowl has started on some of the server side assemblies, but I don't think the Blazor WASM assemblies have been made linker-safe yet.