bevyengine/bevy · error · ReflectedRonSerializeError::MissingSubasset

Expected the root LoadedUntypedHandle to hold a handle to…

Error message

Expected the root LoadedUntypedHandle to hold a handle to its subasset, but it did not have such a subasset

What it means

ReflectedRonSerializeError::MissingSubasset is thrown by the reflected RON saver when the root LoadedUntypedHandle is expected to contain a handle to its subasset but none is present. The serializer needs the typed subasset handle to reach the actual value to serialize.

Solutions

1. Load the asset with the reflected RON loader so the subasset handle is populated before saving
2. Verify the LoadedUntypedHandle actually points at a loaded asset with a subasset prior to save
3. Use the correct saver for assets loaded outside the reflected pipeline

fn can_save(handle: &LoadedUntypedHandle) -> bool {
    handle.clone().get::<bevy_asset::Handle<()>>().is_ok() // subasset present
}

When it happens

Trigger: Calling save/reflected RON serialization on an asset whose LoadedUntypedHandle has no subasset handle attached (asset loaded by a non-reflected path or handle never inserted).

Common situations: Serializing an asset that was constructed manually without going through the reflected loader that populates the subasset; saving before the asset finished loading.

Understand the failure class

Background: "This is a bug, please report it": internal invariant violations, unreachable panics, and SNH errors explained — this error's family across 47 libraries.

Related errors

• Could not parse RON
• Attempted to load type
• Attempted to load type
• Error while trying to read the world file
• Subasset type does not have ReflectFromPtr registered in…

AI-assisted analysis of bevyengine/bevy@a62cce8c05 (2026-09-19). Data as JSON: /api/errors/d19e5f954f124cfa. Report an issue: GitHub.

Appendix: source

Thrown at crates/bevy_asset/src/common_loaders/ron.rs:475

    #[error("Attempted to load type \"{0}\", which does not have `ReflectFromReflect` in the type registry. This may occur for types that have opted-out of `FromReflect`")]
    MissingReflectFromReflect(&'static str),
    #[error("Attempted to load type \"{0}\", which does not have `ReflectAsset` in the type registry. Make sure to add `#[reflect(Asset)]` to your type")]
    MissingReflectAsset(&'static str),
}

/// An error type for RON saving.
#[derive(Error, Debug)]
pub enum RonSerializeError {
    #[error(transparent)]
    IoError(#[from] std::io::Error),
    #[error(transparent)]
    Ron(#[from] ron::Error),
}

/// An error type for RON saving using reflection.
#[derive(Error, Debug)]
pub enum ReflectedRonSerializeError {
    #[error(
        "Expected the root LoadedUntypedHandle to hold a handle to its subasset, but it did not have such a subasset"
    )]
    MissingSubasset,
    #[error("Subasset type was not registered in the TypeRegistry. Ensure your subasset's type implements Reflect (and if it's generic it needs to be manually registered)")]
    ValueNotReflect,
    #[error("Subasset type does not have ReflectFromPtr registered in its type data")]
    MissingReflectFromPtr,
    #[error(transparent)]
    Ron(#[from] RonSerializeError),
}

#[cfg(test)]
mod tests {
    use std::path::Path;

    use alloc::{string::String, vec};

    use bevy_ecs::reflect::AppTypeRegistry;

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