Add trim-safe ValidationContext constructor

[captainsafia]

Resolves #113134

[dotnet-issue-labeler]

Note regarding the new-api-needs-documentation label:

This serves as a reminder for when your PR is modifying a ref *.cs file and adding/modifying public APIs, please make sure the API implementation in the src *.cs file is documented with triple slash comments, so the PR reviewers can sign off that change.

[dotnet-issue-labeler]

Note regarding the new-api-needs-documentation label:

This serves as a reminder for when your PR is modifying a ref *.cs file and adding/modifying public APIs, please make sure the API implementation in the src *.cs file is documented with triple slash comments, so the PR reviewers can sign off that change.

[tarekgh]

Don't we need to modify the options source generator with this PR too?

runtime/src/libraries/Microsoft.Extensions.Options/gen/Emitter.cs

Line 692 in 42bbfeb

OutLn($"var context = new {StaticValidationContextType}(options);");

runtime/src/libraries/Microsoft.Extensions.Options/gen/Emitter.cs

Line 685 in 42bbfeb

OutLn($"[System.Diagnostics.CodeAnalysis.UnconditionalSuppressMessage(\"Trimming\", \"IL2026:RequiresUnreferencedCode\",");

[eerhardt]

Can you update this line?

runtime/src/libraries/System.ComponentModel.Annotations/src/System/ComponentModel/DataAnnotations/ValidationContext.cs

Lines 181 to 182 in d15a82e

	[UnconditionalSuppressMessage("ReflectionAnalysis", "IL2026:RequiresUnreferencedCode", Justification = "The ctors are marked with RequiresUnreferencedCode.")]
	private string? GetDisplayName()

[eerhardt]

Don't we need to modify the options source generator with this PR too?

It still supports netstandard2.0 right? So we would need to switch based off if the code was targeting net10.0+?

[eiriktsarpalis]

Which part of the other constructor forces it to have an RUC annotation? This seems to be replicating most of the statements present in the previous ctor.

[eerhardt]

This code is the reason why the other 2 constructors are marked RUC:

runtime/src/libraries/System.ComponentModel.Annotations/src/System/ComponentModel/DataAnnotations/ValidationContext.cs

Lines 181 to 182 in 5ff417f

	[UnconditionalSuppressMessage("ReflectionAnalysis", "IL2026:RequiresUnreferencedCode", Justification = "The ctors are marked with RequiresUnreferencedCode.")]
	private string? GetDisplayName()

[captainsafia]

I updated the RUC messages here to be a little bit clearer about the fact that the issue is not providing a display name forces us down the path of resolving the type from the object instance which is not trim-safe.

[jeffhandley]

Pretty wild that getting the display name was the pitfall here. Very cool to overcome that, @captainsafia!

[captainsafia]

It still supports netstandard2.0 right? So we would need to switch based off if the code was targeting net10.0+?

I updated the emitter to generate the different invocations behind an #ifdef. Alternatively, we could try to query for the TFM in the source generator itself and change what is emitted there but this felt easier.

Edit: bleh, need to hop on a devbox to update the netfx baselines

[tarekgh]

LGTM. Thanks @captainsafia!