get() function of Array Panics when Element is empty

[Masupell]

When trying to get an item from an Array which got its size manually added in the godot editor and therefore contains no actual items, but only fields, it panics when trying to get it, with no way of preventing it

[Bromeon]

Oh, interesting case, thanks for reporting!

Which element type?

Can you also reproduce this in GDScript, when calling Array.resize()?

[Bromeon]

There's a general issue that array representations in Rust are a bit more strict than in Godot:

• Array[Class] can store nulls, but Array<Gd<Class>> cannot. Would need Array<Option<Gd<Class>>>.
• Array[int] may be represented as Array[u8] on Rust side
  • See Best-effort checks for Array<Integer> conversions; fix Debug for variants containing typed arrays #853.
• The upcoming DynGd<Class, dyn Trait> has Rust-side bounds on a trait.

In this case, there's the problem that Godot expects arrays to be default-constructible, but godot-rust allows them to have arbitrary constructors (and not necessarily a default one). So there's a good chance this issue would be a wontfix due to this discrepancy; requiring default construction just for this use case would be too limiting.

But maybe there are ways we can improve the user experience, e.g. panic message -- how does it look now?

[Bromeon]

So, as mentioned above, I don't think we can fix this -- at least not without crippling Array and only allowing "godot-safe" types. This would mean everyone had to use Option<Gd<T>> for objects inside arrays, no i16 and no DynGd.

I'm not sure this is worth it. Some users only use Godot APIs from Rust and aren't affected by the limitation, but can definitely benefit from better Rust-side type safety. I documented this behavior in Array under section Element type safety. This makes it easy for people who find this important to just stick to the "safe" types like Array<Option<Gd<T>>>.

As such I'll close this as wontfix. If you have more ideas how we could handle such cases, let me know!