ReadLocalValue() is never returning UnsetValue

[ajpinedam]

Current behavior

There are a few places in the Uno code where we use ReadLocalValue to validate whether a DependencyProperty has been set, returning UnsetValue. I have seen situations where we are returning null for DPs that still need to be set, and this behavior change is causing some issues.

Expected behavior

No response

How to reproduce it (as minimally and precisely as possible)

No response

Workaround

N/A

Works on UWP/WinUI

None

Environment

Uno.WinUI / Uno.WinUI.WebAssembly / Uno.WinUI.Skia

NuGet package version(s)

5.6.0-dev.149

Affected platforms

WebAssembly, Android, iOS, Mac Catalyst, Skia (WPF), Skia (Linux X11), Skia (macOS), Skia (Linux Framebuffer), Skia (GTK)

IDE

Visual Studio 2022, Visual Studio Code

IDE version

No response

Relevant plugins

No response

Anything else we need to know?

No response

[ajpinedam]

cc: @Youssef1313 I saw this issue while debugging a fix on PR https://github.com/unoplatform/uno/pull/18492

[Youssef1313]

That's quite strange. The implementation is currently:

https://github.com/unoplatform/uno/blob/b6333bd85ef09975ae45e538230dae337a96e43f/src/Uno.UI/UI/Xaml/DependencyObjectStore.cs#L281-L295

[ajpinedam]

if (details?.GetBaseValueSource() == DependencyPropertyValuePrecedences.Local)

While debugging the code entered here

if (details?.GetBaseValueSource() == DependencyPropertyValuePrecedences.Local) 
{ 
    return details.GetBaseValue(); 
} 

and

return details.GetBaseValue(); 

is returning null instead of UnsetValue

cc: @Youssef1313

[Youssef1313]

That should mean that a local value of null was set. Are you able to track the SetValue calls?

[ajpinedam]

This is for the SelectedItem on the TabView (TabView.Properties file). I set a breakpoint inside the Set, which is never hit before hitting this method call.

We can get some time tomorrow and do a quick sync whenever you're available to look into it

cc: @Youssef1313