slint-ui/slint · error

Global was just valid

Error message

Global was just valid

What it means

Internal invariant panic from `.expect("Global was just valid")` in `query_preview_data_properties_and_callbacks` (tools/lsp/preview/preview_data.rs:157). The global names being queried come from `definition.globals()` on the same `ComponentDefinition` in the same loop iteration, so `definition.global_properties_and_callbacks(&global)` is expected to always succeed (it returns None only for an unknown global). This is the live-preview path that enumerates every global's properties and callbacks for the LSP preview panel.

Solutions

1. Ensure the ComponentInstance and its definition() are from the same compilation; rebuild the instance whenever the definition is recompiled.
2. Replace the expect with graceful degradation: `if let Some(it) = definition.global_properties_and_callbacks(&global) { ... }` so preview data for one bad global doesn't panic the LSP.
3. Check interpreter version consistency — component_instance and definition must come from the same slint_interpreter state.

Example fix

// before
&mut definition.global_properties_and_callbacks(&global).expect("Global was just valid"),
// after
match definition.global_properties_and_callbacks(&global) {
    Some(it) => result.extend(collect_preview_data(PropertyContainer::Global(global.clone()), &mut it, &|name| component_instance.get_global_property(&global, name).ok())),
    None => eprintln!("skipping inconsistent global {global}"),
}

// before querying, verify the global resolves on the same definition instance
if definition.global_properties_and_callbacks(&global).is_none() {
    eprintln!("global {global} missing from definition; instance/definition mismatch");
}

fn global_is_consistent(d: &slint_interpreter::ComponentDefinition, g: &str) -> bool { d.globals().iter().any(|x| x == g) && d.global_properties_and_callbacks(g).is_some() }

// Rust: panics are not catchable idiomatically; replace expect with match
match definition.global_properties_and_callbacks(&global) {
    Some(it) => { /* collect preview data */ }
    None => eprintln!("skipping global {global}: not found in definition"),
}

When it happens

Trigger: Only if the interpreter's ComponentDefinition is inconsistent — i.e. `globals()` yields a name for which `global_properties_and_callbacks` returns None. In practice this would require a mismatched/slanted definition instance, a stale component_instance after recompilation, or misuse of the interpreter internals (e.g. calling this with a ComponentInstance built from a different ComponentDefinition).

Common situations: Developers hit this when mixing a ComponentInstance with a ComponentDefinition obtained from a different compile (e.g. after a hot reload rebuilt definitions but cached the old instance), or after interpreter API changes where globals() and global_properties_and_callbacks() no longer agree.

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

• Length was checked
• Not empty
• There is always one line
• an identifier
• Cannot get property

AI-assisted analysis of slint-ui/slint@bb937076de (2026-09-16). Data as JSON: /api/errors/01af1d07a8f98c62. Report an issue: GitHub.

Appendix: source

Thrown at tools/lsp/preview/preview_data.rs:157

                PreviewDataKey { container: container.clone(), property_name: name },
                PreviewData { ty, visibility, value },
            )
        })
    }

    let mut result = collect_preview_data(
        PropertyContainer::Main,
        &mut definition.properties_and_callbacks(),
        &|name| component_instance.get_property(name).ok(),
    )
    .collect::<PreviewDataMap>();

    for global in definition.globals() {
        result.extend(collect_preview_data(
            PropertyContainer::Global(global.clone()),
            &mut definition
                .global_properties_and_callbacks(&global)
                .expect("Global was just valid"),
            &|name| component_instance.get_global_property(&global, name).ok(),
        ));
    }

    result
}

fn find_component_properties_and_callbacks<'a>(
    definition: &'a slint_interpreter::ComponentDefinition,
    container: &PropertyContainer,
) -> Result<
    Box<
        dyn Iterator<
                Item = (
                    String,
                    (
                        i_slint_compiler::langtype::Type,
                        i_slint_compiler::object_tree::PropertyVisibility,

View on GitHub (pinned to bb937076de)