[BUG] Using IsStringNullOrEmptyConverter to assign AutomationProperties.IsInAccessibleTree causes ArgumentException

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

When using converters from the Maui.CommunityToolkit (in particular, when using the IsStringNotNullOrEmpty converter when trying to set AutomationProperties.IsInAccessibleTree, an ArgumentException is thrown and you are unable to load the page where the converter is used.

I have primarily tested/encountered this issue on iOS and Android, however the attached repo will also show the issue on Windows apps.

See attached StackTrace:

System.ArgumentException: targetType needs to be assignable from System.Boolean. (Parameter 'targetType')
   at CommunityToolkit.Maui.Extensions.ValueConverterExtension.ValidateTargetType[Boolean](Type targetType) in /_/src/CommunityToolkit.Maui/Extensions/ValueConverterExtension.shared.cs:line 65
   at CommunityToolkit.Maui.Converters.BaseConverter`2[[System.String, System.Private.CoreLib, Version=7.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[System.Boolean, System.Private.CoreLib, Version=7.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].CommunityToolkit.Maui.Converters.ICommunityToolkitValueConverter.Convert(Object value, Type targetType, Object parameter, CultureInfo culture) in /_/src/CommunityToolkit.Maui/Converters/BaseConverter.shared.cs:line 165
   at CommunityToolkit.Maui.Converters.ICommunityToolkitValueConverter.Microsoft.Maui.Controls.IValueConverter.Convert(Object value, Type targetType, Object parameter, CultureInfo culture) in /_/src/CommunityToolkit.Maui/Converters/ICommunityToolkitValueConverter.shared.cs:line 52
   at Microsoft.Maui.Controls.Binding.GetSourceValue(Object value, Type targetPropertyType) in D:\a\_work\1\s\src\Controls\src\Core\Binding.cs:line 299
   at Microsoft.Maui.Controls.BindingExpression.ApplyCore(Object sourceObject, BindableObject target, BindableProperty property, Boolean fromTarget) in D:\a\_work\1\s\src\Controls\src\Core\BindingExpression.cs:line 149
   at Microsoft.Maui.Controls.BindingExpression.Apply(Object sourceObject, BindableObject target, BindableProperty property) in D:\a\_work\1\s\src\Controls\src\Core\BindingExpression.cs:line 75
   at Microsoft.Maui.Controls.Binding.Apply(Object context, BindableObject bindObj, BindableProperty targetProperty, Boolean fromBindingContextChanged) in D:\a\_work\1\s\src\Controls\src\Core\Binding.cs:line 136
   at Microsoft.Maui.Controls.BindableObject.SetBinding(BindableProperty targetProperty, BindingBase binding, Boolean fromStyle) in D:\a\_work\1\s\src\Controls\src\Core\BindableObject.cs:line 229
   at Microsoft.Maui.Controls.BindableObject.SetBinding(BindableProperty targetProperty, BindingBase binding) in D:\a\_work\1\s\src\Controls\src\Core\BindableObject.cs:line 205
   at Microsoft.Maui.Controls.Xaml.ApplyPropertiesVisitor.TrySetBinding(Object element, BindableProperty property, String localName, Object value, IXmlLineInfo lineInfo, BindingBase& binding, Exception& exception) in D:\a\_work\1\s\src\Controls\src\Xaml\ApplyPropertiesVisitor.cs:line 539
   at Microsoft.Maui.Controls.Xaml.ApplyPropertiesVisitor.TrySetPropertyValue(Object element, XmlName propertyName, String xKey, Object value, Object rootElement, IXmlLineInfo lineInfo, IServiceProvider serviceProvider, Exception& xpe) in D:\a\_work\1\s\src\Controls\src\Xaml\ApplyPropertiesVisitor.cs:line 409
   at Microsoft.Maui.Controls.Xaml.ApplyPropertiesVisitor.SetPropertyValue(Object xamlelement, XmlName propertyName, Object value, Object rootElement, INode node, HydrationContext context, IXmlLineInfo lineInfo) in D:\a\_work\1\s\src\Controls\src\Xaml\ApplyPropertiesVisitor.cs:line 373
   at Microsoft.Maui.Controls.Xaml.ApplyPropertiesVisitor.Visit(ElementNode node, INode parentNode) in D:\a\_work\1\s\src\Controls\src\Xaml\ApplyPropertiesVisitor.cs:line 120
   at Microsoft.Maui.Controls.Xaml.ElementNode.Accept(IXamlNodeVisitor visitor, INode parentNode) in D:\a\_work\1\s\src\Controls\src\Xaml\XamlNode.cs:line 159
   at Microsoft.Maui.Controls.Xaml.ElementNode.Accept(IXamlNodeVisitor visitor, INode parentNode) in D:\a\_work\1\s\src\Controls\src\Xaml\XamlNode.cs:line 153
   at Microsoft.Maui.Controls.Xaml.RootNode.Accept(IXamlNodeVisitor visitor, INode parentNode) in D:\a\_work\1\s\src\Controls\src\Xaml\XamlNode.cs:line 212
   at Microsoft.Maui.Controls.Xaml.XamlLoader.Visit(RootNode rootnode, HydrationContext visitorContext, Boolean useDesignProperties) in D:\a\_work\1\s\src\Controls\src\Xaml\XamlLoader.cs:line 210
   at Microsoft.Maui.Controls.Xaml.XamlLoader.Load(Object view, String xaml, Assembly rootAssembly, Boolean useDesignProperties) in D:\a\_work\1\s\src\Controls\src\Xaml\XamlLoader.cs:line 78
   at Microsoft.Maui.Controls.Xaml.XamlLoader.Load(Object view, String xaml, Boolean useDesignProperties) in D:\a\_work\1\s\src\Controls\src\Xaml\XamlLoader.cs:line 53
   at Microsoft.Maui.Controls.Xaml.XamlLoader.Load(Object view, Type callingType) in D:\a\_work\1\s\src\Controls\src\Xaml\XamlLoader.cs:line 49
   at Microsoft.Maui.Controls.Xaml.Extensions.LoadFromXaml[MainPage](MainPage view, Type callingType) in D:\a\_work\1\s\src\Controls\src\Xaml\ViewExtensions.cs:line 37
   at ConverterBinding.MainPage.InitializeComponent() in ConverterBinding\ConverterBinding\Microsoft.Maui.Controls.SourceGen\Microsoft.Maui.Controls.SourceGen.CodeBehindGenerator\MainPage.xaml.sg.cs:line 26
   at ConverterBinding.MainPage..ctor() in ConverterBinding\ConverterBinding\MainPage.xaml.cs:line 9
   at ConverterBinding.App..ctor() in ConverterBinding\ConverterBinding\App.xaml.cs:line 9
   at System.Reflection.RuntimeConstructorInfo.Invoke(BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitConstructor(ConstructorCallSite constructorCallSite, RuntimeResolverContext context)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2[[Microsoft.Extensions.DependencyInjection.ServiceLookup.RuntimeResolverContext, Microsoft.Extensions.DependencyInjection, Version=7.0.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60],[System.Object, System.Private.CoreLib, Version=7.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].VisitCallSiteMain(ServiceCallSite callSite, RuntimeResolverContext argument)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitRootCache(ServiceCallSite callSite, RuntimeResolverContext context)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2[[Microsoft.Extensions.DependencyInjection.ServiceLookup.RuntimeResolverContext, Microsoft.Extensions.DependencyInjection, Version=7.0.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60],[System.Object, System.Private.CoreLib, Version=7.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].VisitCallSite(ServiceCallSite callSite, RuntimeResolverContext argument)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.Resolve(ServiceCallSite callSite, ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceProvider.CreateServiceAccessor(Type serviceType)
   at System.Collections.Concurrent.ConcurrentDictionary`2[[System.Type, System.Private.CoreLib, Version=7.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[System.Func`2[[Microsoft.Extensions.DependencyInjection.ServiceLookup.ServiceProviderEngineScope, Microsoft.Extensions.DependencyInjection, Version=7.0.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60],[System.Object, System.Private.CoreLib, Version=7.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]], System.Private.CoreLib, Version=7.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].GetOrAdd(Type key, Func`2 valueFactory)
   at Microsoft.Extensions.DependencyInjection.ServiceProvider.GetService(Type serviceType, ServiceProviderEngineScope serviceProviderEngineScope)
   at Microsoft.Extensions.DependencyInjection.ServiceProvider.GetService(Type serviceType)
   at Microsoft.Maui.MauiContext.WrappedServiceProvider.GetService(Type serviceType) in D:\a\_work\1\s\src\Core\src\MauiContext.cs:line 68
   at Microsoft.Maui.MauiContext.WrappedServiceProvider.GetService(Type serviceType) in D:\a\_work\1\s\src\Core\src\MauiContext.cs:line 68
   at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService(IServiceProvider provider, Type serviceType)
   at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService[IApplication](IServiceProvider provider)
   at Microsoft.Maui.MauiApplication.OnCreate() in D:\a\_work\1\s\src\Core\src\Platform\Android\MauiApplication.cs:line 37
   at Android.App.Application.n_OnCreate(IntPtr jnienv, IntPtr native__this) in /Users/runner/work/1/s/xamarin-android/src/Mono.Android/obj/Release/net7.0/android-33/mcw/Android.App.Application.cs:line 1072
   at Android.Runtime.JNINativeWrapper.Wrap_JniMarshal_PP_V(_JniMarshal_PP_V callback, IntPtr jnienv, IntPtr klazz) in /Users/runner/work/1/s/xamarin-android/src/Mono.Android/Android.Runtime/JNINativeWrapper.g.cs:line 22

Expected Behavior

The converter should correctly return true or false based on the string it is converting, and the AutomationProperties.IsInAccessibleTree property should be set.

Steps To Reproduce

1. Open and run solution in debug mode from provided repo
2. The app will throw an exception
3. In MainPage.xaml, swap out the current StackLayout for the commented StackLayout to observe the app loading successfully without issue

Link to public reproduction project repository

https://github.com/BruceTheBrick/ConverterBinding

Environment

- .NET MAUI CommunityToolkit: 5.2.0
- OS: Windows 11, Windows 10
- .NET MAUI: 7.0.92/7.0.100

Anything else?

No response

[BruceTheBrick]

Oh AutomationProperties.IsInAccessibleTree is a bool? I bet it’s the nullability that is causing the validation to fail

You may be onto something there. I have noticed that using the same IsStringNotNullOrEmptyConverter on a different property, say for example IsVisible does not seem to throw the same exception. I will check to see if creating a bindable bool? property and using this converter there will cause the same problems.

[bijington]

Oh AutomationProperties.IsInAccessibleTree is a bool? I bet it’s the nullability that is causing the validation to fail