[BUG] NativeAOT Trim warnings

[trampster]

Is there an existing issue for this?

• I have searched the existing issues

Did you read the "Reporting a bug" section on Contributing file?

• I have read the "Reporting a bug" section on Contributing file: https://github.com/CommunityToolkit/Maui/blob/main/CONTRIBUTING.md#reporting-a-bug

Current Behavior

The following Trim warnings are geneated when trying to use the CommunityToolkit with NativeAOT in .net 9 Maui on iOS:

 ILC : Trim analysis warning IL2092: CommunityToolkit.Maui.Converters.ICommunityToolkitValueConverter.Microsoft.Maui.Controls.IValueConverter.Convert(Object,Type,Object,CultureInfo): 'DynamicallyAccessedMemberTypes' in 'DynamicallyAccessedMembersAttribute' on the parameter '' of method 'CommunityToolkit.Maui.Converters.ICommunityToolkitValueConverter.Microsoft.Maui.Controls.IValueConverter.Convert(Object,Type,Object,CultureInfo)' don't match overridden parameter '' of method 'Microsoft.Maui.Controls.IValueConverter.Convert(Object,Type,Object,CultureInfo)'. All overridden members must have the same 'DynamicallyAccessedMembersAttribute' usage.
    ILC : Trim analysis warning IL2092: CommunityToolkit.Maui.Converters.ICommunityToolkitValueConverter.Microsoft.Maui.Controls.IValueConverter.ConvertBack(Object,Type,Object,CultureInfo): 'DynamicallyAccessedMemberTypes' in 'DynamicallyAccessedMembersAttribute' on the parameter '' of method 'CommunityToolkit.Maui.Converters.ICommunityToolkitValueConverter.Microsoft.Maui.Controls.IValueConverter.ConvertBack(Object,Type,Object,CultureInfo)' don't match overridden parameter '' of method 'Microsoft.Maui.Controls.IValueConverter.ConvertBack(Object,Type,Object,CultureInfo)'. All overridden members must have the same 'DynamicallyAccessedMembersAttribute' usage.
    ILC : Trim analysis warning IL2092: CommunityToolkit.Maui.Converters.ICommunityToolkitValueConverter.Microsoft.Maui.Controls.IValueConverter.Convert(Object,Type,Object,CultureInfo): 'DynamicallyAccessedMemberTypes' in 'DynamicallyAccessedMembersAttribute' on the parameter '' of method 'CommunityToolkit.Maui.Converters.ICommunityToolkitValueConverter.Microsoft.Maui.Controls.IValueConverter.Convert(Object,Type,Object,CultureInfo)' don't match overridden parameter '' of method 'Microsoft.Maui.Controls.IValueConverter.Convert(Object,Type,Object,CultureInfo)'. All overridden members must have the same 'DynamicallyAccessedMembersAttribute' usage.
    ILC : Trim analysis warning IL2092: CommunityToolkit.Maui.Converters.ICommunityToolkitValueConverter.Microsoft.Maui.Controls.IValueConverter.ConvertBack(Object,Type,Object,CultureInfo): 'DynamicallyAccessedMemberTypes' in 'DynamicallyAccessedMembersAttribute' on the parameter '' of method 'CommunityToolkit.Maui.Converters.ICommunityToolkitValueConverter.Microsoft.Maui.Controls.IValueConverter.ConvertBack(Object,Type,Object,CultureInfo)' don't match overridden parameter '' of method 'Microsoft.Maui.Controls.IValueConverter.ConvertBack(Object,Type,Object,CultureInfo)'. All overridden members must have the same 'DynamicallyAccessedMembersAttribute' usage.
    /_/src/CommunityToolkit.Maui/Extensions/ValueConverterExtension.shared.cs(31): Trim analysis warning IL2062: CommunityToolkit.Maui.Extensions.ValueConverterExtension.IsValidTargetType<TTarget>(Type&,Boolean): Value passed to parameter 'type' of method 'System.Activator.CreateInstance(Type)' can not be statically determined and may not meet 'DynamicallyAccessedMembersAttribute' requirements.

Expected Behavior

No Trim warnings

Reproduction Sample

https://github.com/trampster/MauiCommunityToolkitTrimIssue

Steps To Reproduce

1. Create a MAUI project that targets iOS with .net 9 MAUI
2. Add reference to CommCommunityToolkit.Maui <PackageReference Include="CommunityToolkit.Maui" Version="10.0.0" />
3. Use the InvertedBoolConverter in xaml
4. Add bits required to turn on NativeAOT:

<IsAotCompatible>true</IsAotCompatible>
<PublishAot Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'ios'">true</PublishAot>

4. Build using dotnet publish -f net9.0-ios -r ios-arm64
   -> trim warnings from description

Link to public reproduction project repository

MauiCommunityToolkitTrimIssue

Environment

- .NET MAUI CommunityToolkit: 10.0.0
- OS: iOS
- .NET MAUI: 9.0.21

Anything else?

No response

[dotnet-policy-service]

Hi @trampster! We have added the needs reproduction label to this issue, which indicates that we are unable to take further action until you provide a reproduction sample that we can use to reproduce + fix your bug. In accordance with the Reporting a bug section of our Contributing.md that you confirmed reading before you submitted this Issue, we ask that every Issue author provide a link to an open-source repository containing the reproduction sample app. This issue will be closed automatically in 5 days if we do not receive a reproduction sample from you. Please feel free to re-open this Issue once you have provided a reproduction sample.

[trampster]

I have added a link to a reproduction sample. https://github.com/trampster/MauiCommunityToolkitTrimIssue

[trampster]

As a work arround we have created our own InvertBoolConverter that does not produce trim warnings:

[AcceptEmptyServiceProvider]
public class InvertBoolConverter : IValueConverter
{
   public object Convert(object? value, Type targetType, object? parameter, System.Globalization.CultureInfo culture)
   {
      return !((bool)(value ?? false));
   }

   public object ConvertBack(object? value, Type targetType, object? parameter, System.Globalization.CultureInfo culture)
   {
      return value ?? false;
   }
}

Feel free to use this until the Maui CommunityToolkit is fixed.

[jfversluis]

@simonrozsival is there any way to prevent this other than to use #pragma disable?

[simonrozsival]

@jfversluis The reason the warnings are shown is that
the ICommunityToolkitValueConverter adds [DynamicallyAccessedMembers] attribute to parameters that don't have it in the base IValueConverter definition:

Maui/src/CommunityToolkit.Maui/Converters/ICommunityToolkitValueConverter.shared.cs

Lines 55 to 62 in e66f78e

	#pragma warning disable IL2092
	object? IValueConverter.Convert(object? value, [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicParameterlessConstructor)] Type targetType, object? parameter, CultureInfo culture) =>
	Convert(value, targetType, parameter, culture);
	/// <inheritdoc />
	object? IValueConverter.ConvertBack(object? value, [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicParameterlessConstructor)] Type targetType, object? parameter, CultureInfo culture) =>
	ConvertBack(value, targetType, parameter, culture);
	#pragma warning restore IL2092

vs. https://github.com/dotnet/maui/blob/1807a6c10fb5ebeb14c0f24883acb3cbddd97a52/src/Controls/src/Core/IValueConverter.cs

The #pragma warning disable IL2092 silences the roslyn analyzer, but when the NativeAOT compiler (ILC) later compiles the IL, it won't see that #pragma. Instead, it is necessary to use [UnconditionalSuppressMessage] to completely silence those warnings. Something like this should do the trick:

object? IValueConverter.Convert(object? value, Type targetType, object? parameter, CultureInfo culture)
{
	return _Convert();

        [UnconditionalSuppressMessage("TrimAnalysis", "IL2092", Justification = "The ToType and FromType properties are attributed with the  appropriate DynamicallyAccessedMembers attributes.")]
	object? _Convert() => Convert(value, targetType, parameter, culture);
}

[jfversluis]

@trampster would you be able to test the resulting NuGets from this PR build to verify if that fixes this scenario for you in your project?