[.Net] The key for exported `Godot.Collections.Dictionary<Node, ...>` becomes `null` in runtime

[Delsin-Yu]

Tested versions

v4.4.stable.mono.official [4c311cb]
v4.4.1.stable.mono.official [49a5bc7]

System information

Godot v4.4.stable.mono - Windows 10 (build 19044) - Multi-window, 4 monitors - Vulkan (Forward+) - dedicated NVIDIA GeForce RTX 4060 Ti (NVIDIA; 32.0.15.7283) - AMD Ryzen 9 5900X 12-Core Processor (24 threads)

Issue description

Consider the following example and scene setup:

using Godot;

public partial class Main : Node
{
    [Export] private Godot.Collections.Dictionary<Node2D, int> _data;

    public override void _Ready()
    {
        foreach (var pair in _data)
        {
            GD.Print(pair.Key);
            GD.Print(pair.Value);
        }
    }
}

[gd_scene load_steps=2 format=3 uid="uid://dnrcj8m6viwfu"]

[ext_resource type="Script" uid="uid://bidx84qegm2nn" path="res://Main.cs" id="1_ig7tw"]

[node name="Control" type="Node" node_paths=PackedStringArray("_data")]
script = ExtResource("1_ig7tw")
_data = {
NodePath("Node2D"): 0,
NodePath("Node2D2"): 1
}

[node name="Node2D" type="Node2D" parent="."]

[node name="Node2D2" type="Node2D" parent="."]

When running the scene, the output is the following:

null
0
null
1

Where when using GDScript:

extends Node

@export var _data : Dictionary[Node2D, int];

func _ready() -> void:
	for key in _data:
		print(key);
		print(_data[key]);

The output is correct:

Node2D:<Node2D#29813114202>
0
Node2D2:<Node2D#29829891419>
1

This Issue only happens when the key is Node type, NodePath as key functions correctly.

Steps to reproduce

1. Download and Open the MRP
2. Build and run the project
3. Inspect the incorrect output from Main.cs
4. Swap the script from Main.cs to main.gd
5. Run the project
6. Inspect the correct output from main.gd

Minimal reproduction project (MRP)

MrpNodeTypedDictKeyBecomesNull.zip

[AThousandShips]

Can you please test with a supported version like 4.4.1? To ensure this has not already been fixed

[Delsin-Yu]

To ensure this has not already been fixed

Also reproductable in 4.4.1

[raulsntos]

Seems like a duplicate of #97850. Try inline initialization:

[Export] private Godot.Collections.Dictionary<Node2D, int> _data = new();

[Delsin-Yu]

I can confirm that inline initialization does work.