Microsoft.NET.Sdk.Web should default to TrimMode=full

[eerhardt]

Today, we are defaulting TrimMode=partial in Microsoft.NET.Sdk.Web:

sdk/src/WebSdk/Publish/Targets/Microsoft.NET.Sdk.Publish.targets

Lines 89 to 90 in 67b5915

	<!-- If TrimMode has not already been set, default to partial trimming, as AspNet is not currently fully trim-compatible -->
	<TrimMode Condition="'$(PublishTrimmed)' == 'true' and '$(TrimMode)' == ''">partial</TrimMode>

    <!-- If TrimMode has not already been set, default to partial trimming, as AspNet is not currently fully trim-compatible -->
    <TrimMode Condition="'$(PublishTrimmed)' == 'true' and '$(TrimMode)' == ''">partial</TrimMode>

In the "api" template being added in dotnet/aspnetcore#46064, we are explicitly setting TrimMode=full.

Instead, we should do one of the following:

1. Remove the above code, and just let the TrimMode=full default from the runtime be applied to Microsoft.NET.Sdk.Web projects.
2. Change the default to partial only if we aren't also publishing for NativeAOT. Basically adding and '$(PublishAot)' != 'true' above.

My goal would be we do (1). For places in ASP.NET that aren't fully trim-compatible, the app developer should get a warning (even from within ASP.NET code) to tell them what are things that aren't going to work.

We may consider just doing (2) in .NET 8, until things like MVC and Razor pages work correctly in fully trimmed apps.

cc @JamesNK @DamianEdwards @davidfowl

[ghost]

@dotnet/linker-contrib a new issue has been filed in the ILLink area, please triage

[halter73]

We should think about defaulting to full with PublishTrimmed true as well

#29984 (comment)

There's some debate one whether we'll be ready in .NET 8, but we will keep this issue open to track changing the TrimMode default from "partial" to "full" like the Microsoft.NET.Sdk default.

[mkArtakMSFT]

@adityamandaleeka assigning this to you as this is minimal related.

[eerhardt]

as this is minimal related.

Note that this issue applies to "all" ASP.NET server app models - minimal APIs, MVC, Razor Pages, etc.

[agocke]

I would go for (1) as well.

That code was specifically meant to provide compatibility for Blazor WASM, which was a pre-existing trimming scenario. Having it apply to all of ASP.NET wasn't really intentional on my part.

partial isn't really intended for new trimming scenarios. It has no effect on trim warnings, so it doesn't really help in the task of making things trim compatible, and our current goal for trimming is to give users a very clear statement on whether or not their app works, based on the warning behavior.

[adityamandaleeka]

@eerhardt Can this be closed now?

[eerhardt]

Yes, this was fixed with #33962 and #34030.