DataContext value in DevTools displayed as null if type of value inherited from System.ComponentModel.Component

[BreakByBrick]

Describe the bug

Hello!

When ViewModel is inherited from System.ComponentModel.Component, it displays in DataContext value of DevTools.

But in debug DataContext has value.

To Reproduce

https://github.com/BreakByBrick/Avalonia.Issue/tree/main/DevTools.DataContextWithComponentDisplaysNull

Expected behavior

The DataContext value in DevTools must not be null.

Avalonia version

11.0.10

OS

Windows

Additional context

No response

[stevemonaco]

The type to text ultimately goes through:

Avalonia/src/Avalonia.Diagnostics/Diagnostics/Views/PropertyValueEditorView.cs

Lines 345 to 355 in 9be975b

	public static string? ToString(object o)
	{
	var converter = TypeDescriptor.GetConverter(o);
	//CollectionConverter does not deliver any important information. It just displays "(Collection)".
	if (!converter.CanConvertTo(typeof(string)) ||
	converter.GetType() == typeof(CollectionConverter))
	return o.ToString();
	return converter.ConvertToInvariantString(o);
	}

Component has a .NET type, ComponentConverter, that is being used to ConvertToInvariantString(...) which goes through ConvertTo in this case. Component and string aren't really convertible, so it returns null.

So the fix is probably to add another special case to the if so the type name is returned:

if (!converter.CanConvertTo(typeof(string)) ||
    converter.GetType() == typeof(CollectionConverter) ||
    converter.GetType() == typeof(ComponentConverter))
    return o.ToString();

I can PR if this seems reasonable to a maintainer. I'm not familiar with Component at all. ie. Should we force the type string to be returned or can/should the app dev write a custom+default implementation?

[jp2masa]

Maybe it should just fallback to o.ToString()?

return converter.ConvertToInvariantString(o) ?? o.ToString();

or

if (!converter.CanConvertTo(typeof(string)) ||
    converter.GetType() == typeof(CollectionConverter) ||
    converter.ConvertToInvariantString(o) is not { } converted)
    return o.ToString();

return converted;

[stevemonaco]

I misdiagnosed because this is a bit nonsensical. converter.ConvertToInvariantString(o) for ComponentConverter actually returns an empty string after double-checking, so null fallback won't work. DevTools then somewhere along the line interprets this as (null) and I don't yet understand how/where.

Even simpler, you can repro with <TextBlock Text="" />, on 11.0.10 and nightly. The DevTools display will be (null).

Explicit ComponentConverter check might still be necessary?