C#: Adding = new Array<int>() when declaring an int array Export, makes 0 be considered a null value instead of 0

[cjohnson57]

Tested versions

4.3 stable, as well as 4.3.dev5

System information

Godot v4.3.stable.mono - Windows 10.0.22631 - Vulkan (Forward+) - dedicated NVIDIA GeForce RTX 2070 SUPER (NVIDIA; 32.0.15.6081) - AMD Ryzen 9 3900X 12-Core Processor (24 Threads)

Issue description

In C#, using Godot.Collections.Array<int>, I ran into the following obscure issue. My habit when declaring class variables is usually to initialize them, so I did so like this:

[Export]
public Array<int> includedPanels = new Array<int>();

After doing so, I initialized the array in the editor and added a value of 0 to it. However, upon running includedPanels.Contains(0) on it, I was surprised that it returned false.

Eventually, I realized that the 0 was actually being stored as null. Bizarrely, I figured out that, if I remove the = new Array<int>(), then rebuild the project and re-initialize the array, then the 0 is actually stored as 0. I changed my declaration like so, before building, resetting the array in the editor, and initializing it again:

[Export]
public Array<int> includedPanels;

And this produced the following change (screenshot from my Git client):

Steps to reproduce

Create a class and attach its script to a node.

Add the following properties to the class:

[Export]
public Array<int> noInitialValue;

[Export]
public Array<int> initialValue = new Array<int>();

Build the project, and then, in the editor, click on the node the script is attached to. Initialize both arrays with a value of 0. Open the scene file in a text editor, and you will see that the first contains 0 and the other contains null.

Minimal reproduction project (MRP)

N/A

[raulsntos]

This is probably because Godot.Collections.Array<T> does not set the underlying array type, so the editor stores an untyped array, and when you add an element to it, it adds a default Variant which is null.

[cjohnson57]

This is probably because Godot.Collections.Array<T> does not set the underlying array type, so the editor stores an untyped array, and when you add an element to it, it adds a default Variant which is null.

That's interesting, thanks for the insight!

[a-johnston]

This is probably because Godot.Collections.Array<T> does not set the underlying array type, so the editor stores an untyped array, and when you add an element to it, it adds a default Variant which is null.

@raulsntos would it be reasonable to add an alternative godotsharp_array_new which accepts type information, so that when some Array<T> is created from the c# side the native value can have set_typed called as appropriate? Or potentially some new godotsharp_array_set_typed for the Array<T> constructor to invoke? I probably would bias towards the former to reduce native calls but the latter feels a bit cleaner.

I guess it's a bit weird in either case because in every scenario besides changing c# arrays from the editor it's c# handling type validation anyways.

[raulsntos]

We likely want to match what godot-cpp is doing and call Array::set_typed in the constructor¹. There's already a PR that I think does this but I haven't had a chance to review it yet:

• Fix generic arrays and dictionaries in .NET not calling set_typed #98545

Footnotes

1. https://github.com/godotengine/godot-cpp/blob/a98d41f62bdb8b7aa903e8e37c1faa48fe8fdae8/include/godot_cpp/variant/typed_array.hpp#L58 ↩