bevyengine/bevy · error · ResourceFetchError::NotRegistered

The resource has never been initialized or registered with t

Error message

The resource has never been initialized or registered with the world. Did you forget to add it using `app.insert_resource` / `app.init_resource`?

What it means

ResourceFetchError::NotRegistered: the requested resource type has never been initialized or registered in this world — its component id does not exist, so no amount of current-state checking will find it.

Source

Thrown at crates/bevy_ecs/src/world/error.rs:68

#[derive(thiserror::Error, Debug, Clone, Copy, PartialEq, Eq)]
pub enum EntityMutableFetchError {
    /// The entity is not spawned.
    #[error(
        "{0}\n
    If you were attempting to apply a command to this entity,
    and want to handle this error gracefully, consider using `EntityCommands::queue_handled` or `queue_silenced`."
    )]
    NotSpawned(#[from] EntityNotSpawnedError),
    /// The entity with the given ID was requested mutably more than once.
    #[error("The entity with ID {0} was requested mutably more than once")]
    AliasedMutability(Entity),
}

/// An error that occurs when getting a resource of a given type in a world.
#[derive(thiserror::Error, Debug, Clone, Copy, PartialEq, Eq)]
pub enum ResourceFetchError {
    /// The resource has never been initialized or registered with the world.
    #[error("The resource has never been initialized or registered with the world. Did you forget to add it using `app.insert_resource` / `app.init_resource`?")]
    NotRegistered,
    /// The resource with the given [`ComponentId`] does not currently exist in the world.
    #[error("The resource with ID {0:?} does not currently exist in the world.")]
    DoesNotExist(ComponentId),
    /// Cannot get access to the resource with the given [`ComponentId`] in the world as it conflicts with an on going operation.
    #[error("Cannot get access to the resource with ID {0:?} in the world as it conflicts with an on going operation.")]
    NoResourceAccess(ComponentId),
    /// Tried to mutably fetch an immutable resource.
    #[error("Tried to mutably fetch resource with ID {0:?}, which is immutable")]
    Immutable(ComponentId),
}

#[cfg(test)]
mod tests {
    use crate::{
        prelude::*,
        system::{command::trigger, RunSystemOnce},
    };

View on GitHub (pinned to 396ca72708)

Solutions

1. Call app.insert_resource(value) or app.init_resource::<R>() before fetching
2. In tests, init the resource on the fixture world before running systems
3. Match on ResourceFetchError to handle the missing case gracefully

When it happens

Trigger: Thrown at crates/bevy_ecs/src/world/error.rs:68 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of bevyengine/bevy@396ca72708 (2026-08-20). Data as JSON: /api/errors/47c5b0a8e00a8382. Report an issue: GitHub.