[Source Generators] Add ability to define access modifier for `ObservablePropertyAttribute`

[Javier "Ciberman" Mora]

Overview

For source generators, a lot of times it is needed to expose only the getter of a property and make the setter protected (or even private).

The use case is when a property should only be changed from inside a command and not from the outside.

Currently, adding an [ObservableProperty] attribute, makes the property public get and public set.

API breakdown

I would add an optional parameter to the ObservablePropertyAttribute constructor:

public ObservablePropertyAttribute();

public ObservablePropertyAttribute(PropertyAccess setter);

public ObservablePropertyAttribute(PropertyAccess setter, PropertyAccess getter);

The enum:

// Same order as: https://learn.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/access-modifiers
public enum PropertyAccess
{
    Public = 0,
    Private,
    Protected,
    Internal,
    ProtectedInternal,
    PrivateProtected,
}

Usage example

[ObservableProperty(setter: PropertyAccess.Protected)]
private int _counter = 0;

will generate something like this:

private int _counter = 0;

public Counter
{
    get => _counter;
    protected setter => SetProperty(ret _counter, value);
}

Breaking change?

No

Alternatives

The alternative is not use source generators at all. Or expose the setter, knowing that is a design flaw in the ViewModel API.

Additional context

No response

Help us help you

No, just wanted to propose this

[Sergio Pedri]

Duplicate of #291.
Superseded by #555.