bevyengine/bevy · error

Missing `relationship_target = X` attribute

Error message

Missing `relationship_target = X` attribute

What it means

Compile error from parsing #[relationship_target] attribute options in the Relationship derive macro: the parser saw the `relationship_target` keyword but failed to consume the required `= X` (target relationship type) part, or an unrecognized token followed it. The lookahead1 error is a generic sentinel for a malformed attribute token stream at that position.

Source

Thrown at crates/bevy_ecs/macro_logic/src/component.rs:755

        while !input.is_empty() {
            let lookahead = input.lookahead1();
            if lookahead.peek(kw::allow_self_referential) {
                input.parse::<kw::allow_self_referential>()?;
                allow_self_referential = true;
            } else if lookahead.peek(kw::relationship_target) {
                input.parse::<kw::relationship_target>()?;
                input.parse::<Token![=]>()?;
                relationship_target = Some(input.parse()?);
            } else {
                return Err(lookahead.error());
            }
            if !input.is_empty() {
                input.parse::<Token![,]>()?;
            }
        }
        Ok(Relationship {
            relationship_target: relationship_target.ok_or_else(|| {
                syn::Error::new(input.span(), "Missing `relationship_target = X` attribute")
            })?,
            allow_self_referential,
        })
    }
}

impl Parse for RelationshipTarget {
    fn parse(input: syn::parse::ParseStream) -> Result<Self> {
        let mut relationship: Option<Type> = None;
        let mut linked_spawn: bool = false;

        while !input.is_empty() {
            let lookahead = input.lookahead1();
            if lookahead.peek(kw::linked_spawn) {
                input.parse::<kw::linked_spawn>()?;
                linked_spawn = true;
            } else if lookahead.peek(kw::relationship) {
                input.parse::<kw::relationship>()?;

View on GitHub (pinned to 396ca72708)

Solutions

1. Write the attribute as #[relationship_target = RelationshipType] with a literal `=` and a valid type path
2. Ensure no stray tokens or typos (e.g. missing comma between attribute options like relationship_target = X, relationship_verified) follow the value
3. Separate multiple options with commas: #[relationship_target = Child, relationship_verified)]

When it happens

Trigger: Thrown at crates/bevy_ecs/macro_logic/src/component.rs:755 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/d4a847285acd65c6. Report an issue: GitHub.