NestedLoader can panic from UnapprovedPathMode

[MickHarrigan]

Bevy version and features

v0.18.0-dev @ c392d28d

Relevant system information

MacOS 15.6.1 M4 Max

$ cargo --version
cargo 1.89.0 (c24e10642 2025-06-23)

What you did

Example here.

$ cargo run --example asset_folder

Trying to load a path that is unapproved from the NestedLoader<'_,'_, StaticTyped, Deferred> returns a default Handle, which is later unwrapped.

bevy/crates/bevy_asset/src/loader_builders.rs

Lines 307 to 321 in c392d28

	let handle = if self.load_context.should_load_dependencies {
	self.load_context.asset_server.load_with_meta_transform(
	path,
	self.meta_transform,
	(),
	true,
	)
	} else {
	self.load_context
	.asset_server
	.get_or_create_path_handle(path, self.meta_transform)
	};
	// `load_with_meta_transform` and `get_or_create_path_handle` always returns a Strong
	// variant, so we are safe to unwrap.
	let index = (&handle).try_into().unwrap();

Specifically line 507.

bevy/crates/bevy_asset/src/server/mod.rs

Lines 493 to 524 in c392d28

	pub(crate) fn load_with_meta_transform<'a, A: Asset, G: Send + Sync + 'static>(
	&self,
	path: impl Into<AssetPath<'a>>,
	meta_transform: Option<MetaTransform>,
	guard: G,
	override_unapproved: bool,
	) -> Handle<A> {
	let path = path.into().into_owned();
	if path.is_unapproved() {
	match (&self.data.unapproved_path_mode, override_unapproved) {
	(UnapprovedPathMode::Allow, _) | (UnapprovedPathMode::Deny, true) => {}
	(UnapprovedPathMode::Deny, false) | (UnapprovedPathMode::Forbid, _) => {
	error!("Asset path {path} is unapproved. See UnapprovedPathMode for details.");
	return Handle::default();
	}
	}
	}
	let mut infos = self.write_infos();
	let (handle, should_load) = infos.get_or_create_path_handle::<A>(
	path.clone(),
	HandleLoadingMode::Request,
	meta_transform,
	);
	if should_load {
	self.spawn_load_task(handle.clone().untyped(), path, infos, guard);
	}
	handle
	}

What went wrong

This causes a panic in the IoTaskPool along with a failure to actually get the handle.

2025-10-17T19:08:37.005590Z ERROR bevy_asset::server: Asset path /tmp/bevy/examples/asset/folder/assets/primary/first.txt is unapproved. See UnapprovedPathMode for details.

thread 'IO Task Pool (3)' panicked at /tmp/bevy/crates/bevy_asset/src/loader_builders.rs:321:42:
called `Result::unwrap()` on an `Err` value: UuidNotSupportedError
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
2025-10-17T19:08:37.056995Z ERROR bevy_asset::server: Failed to load asset 'primary', asset loader 'asset_folder::MyAssetLoader' panicked

Additional information

I haven't dug into the other NestedLoader types to see if the same or similar problems exist in those.

My reproduction example is already pretty non-standard and has other issues, explained below.

Example

In the case of setting UnapprovedPathMode::Allow and calling FolderLoader directly, everything is fine.

Else if UnapprovedPathMode is not Allow the crash occurs as described above.

Then finally otherwise if trying to use the load_context to load the Folder immediately the handles are seemingly dropped.
This is what I was actually trying to figure out before finding the panic in the first place.