Clarify Node::duplicate() semantics on #[var] and #[export] fields

[DominikMendel]

This currently doesn't compile because of an importer area. So please don't merge lol.

But should hopefully be fixed soon. Still will take any feedback. Like I'm unsure if it's wise in test cases to run unwrap() on the things that should be Some given the context.

[Bromeon]

Thanks a lot for your contribution, it looks really good for your first pull request! 😊

One thing I've noticed is that a lot of the test assertions aren't testing the duplicate() functionality itself, but a lot around that. We don't need to check if setting a field works or if cloning Gd functions correctly, as we have already dedicated tests for those things elsewhere. So it would be good if assert_eq statements could focus on checks after Node::duplicate() is invoked. Which you do at the end 👍

I also made a comment about Area2D. Let's try to get this problem reproduced with Area2D, and later we can see if we can reduce it even further, to show the problem with only Node. But for now, focus on the first step that demonstrates the problem with Area2D 🙂

[Bromeon]

As this uses default values for every field, it can be generated.

This can be done on the struct declaration above, by adding init:

#[derive(GodotClass)]
#[class(init, base=Node)]

[DominikMendel]

Addressed.

[Bromeon]

Again, just tests what was set. The idea of adding this test is to check if Node::duplicate() copies the values, not if manually setting them works.

[DominikMendel]

Understood. Addressed.

[Bromeon]

You can extract this into a variable, and then use everywhere:

let duplicated = duplicated_obj.bind();

[DominikMendel]

Done.

[DominikMendel]

@Bromeon I tried the changes to the codegen file but couldn't get it to compile. See previous comment thread : #1141 (comment)

Even with this removed I still couldn't get the test to pass, even without assert_eq!(). So I am not sure what I am doing wrong. I even added some free()s on all the objects I manually created. No luck. Open to any help.

[GodotRust]

API docs are being generated and will be shortly available at: https://godot-rust.github.io/docs/gdext/pr-1141

[DominikMendel]

Here's the code failure after the duplication:

Run Godot integration tests...
  Focused run -- execute only selected Rust tests.
  Rust: found 1 tests in 1 files.

   property_test.rs:
   -- test_some_duplicator ... ERROR: [panic itest/rust/src/object_tests/property_test.rs:581]
  assertion `left == right` failed
    left: 0
   right: 5
  Context: itest `test_some_duplicator` failed
   at: godot_core::private::set_gdext_hook::{{closure}} (godot-core/src/private.rs:303)
(backtrace disabled, run application with `RUST_BACKTRACE=1` environment variable)
   -- test_some_duplicator ... FAILED

Test result: FAILED. 0 passed; 1 failed (focused run).
  Time: 0.00s.

  Failed tests:
  * property_test.rs > test_some_duplicator

Which is this line

        assert_eq!(duplicated.int_val, 5);

[Bromeon]

Hm... Node::duplicate() is documented as:

Duplicates the node, returning a new node with all of its properties, signals, groups, and children copied from the original. The behavior can be tweaked through the flags (see DuplicateFlags).

I wonder if this behavior is different in GDScript?
Or only applies to exported properties?

[DominikMendel]

Hm... Node::duplicate() is documented as:

Duplicates the node, returning a new node with all of its properties, signals, groups, and children copied from the original. The behavior can be tweaked through the flags (see DuplicateFlags).

I wonder if this behavior is different in GDScript? Or only applies to exported properties?

Yeah I'm not too sure how to proceed from here. I haven't really used GDScript, so I don't think I can provide much input there.

But I did get my previous information from the link you provided about it duplicated all the properties.

[Bromeon]

@DominikMendel so I looked into this and debugged a bit.

Turns out duplicating user-defined #[var] properties works fine, we just need to mark them with the storage attribute. I cleaned up the test case and extended it with different ways to do this, plus a plain #[var] which is expected to fail.

Once we have the capability to add per-method custom docs, we can document this behavior for Node::duplicate(). Or maybe make this a proper method Gd::duplicate(), which is returns Gd<T> instead of Option<Gd<Node>>.

Thank you for the reproducible test case!