Node::get_node unexpected panic when given a path to a non-existent node

[davehadley]

When I use Node::get_node to retrieve a Node that does not exist, according to the documentation

null is returned and an error is logged. Attempts to access methods on the return value will result in an “Attempt to call on a null instance.”. 

so I expected that null would map to None in rust. Instead get_node panics with the message Unexpected variant type: InvalidNil. This was discussed on Discord and recommended to be reported here.

A short example that reproducers this panic:

use gdnative::prelude::*;

#[derive(NativeClass)]
#[inherit(Node)]
struct ExampleGetNodeThatDoesNotExistPanics {}

impl ExampleGetNodeThatDoesNotExistPanics {
    fn new(_base: &Node) -> Self {
        Self {}
    }
}

#[methods]
impl ExampleGetNodeThatDoesNotExistPanics {

    #[method]
    fn _ready(&mut self, #[base] _base: &Node) {
        godot_print!("ExampleGetNodeThatDoesNotExistPanics _ready about to get_node");
        let _ = _base.get_node("does not exist"); // panics with message: "Unexpected variant type: InvalidNil"
        godot_print!("ExampleGetNodeThatDoesNotExistPanics this line never executes due to panic");
    }
}

fn init(handle: InitHandle) {
    handle.add_class::<ExampleGetNodeThatDoesNotExistPanics>();
}


godot_init!(init);

and the error message and backtrace:

ERROR: (Node not found: "does not exist" (relative to "/root/Scene").)
   at: get_node (scene/main/node.cpp:1465)
thread '<unnamed>' panicked at 'Unexpected variant type: InvalidNil', /home/dave/home/gdnative-get-node-panic-example/target/debug/build/gdnative-bindings-cfa8e4943b33c4de/out/generated.rs:1977:23307
stack backtrace:
   0: rust_begin_unwind
             at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/std/src/panicking.rs:575:5
   1: core::panicking::panic_fmt
             at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/core/src/panicking.rs:65:14
   2: core::result::unwrap_failed
             at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/core/src/result.rs:1791:5
   3: core::result::Result<T,E>::expect
             at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/core/src/result.rs:1070:23
   4: gdnative_bindings::generated::node::<impl gdnative_bindings::generated::node::private::Node>::get_node
             at /home/dave/home/gdnative-get-node-panic-example/target/debug/build/gdnative-bindings-cfa8e4943b33c4de/out/generated.rs:1977:23209
   5: gdnative_get_node_panic_example::ExampleGetNodeThatDoesNotExistPanics::_ready

A small Godot project reproducing the problem: gdnative-get-node-panic-example.zip

[davehadley]

In case someone else has run into the same problem, I am documenting here the workarounds suggested on the discord by @chitoyuu and thomastc.

• Check Node::has_node
• Enable crate ptrcall feature.