biomejs/biome · error

formatting embedded JavaScript snippets requires the `js_emb

Error message

formatting embedded JavaScript snippets requires the `js_embeds` feature

What it means

Panic in the embedded-formatting closure of the JavaScript handler (javascript.rs:1755-1766). When biome_service is compiled without the js_embeds cargo feature, formatting a document that contains embedded snippets (e.g. CSS or GraphQL inside JS template literals) reaches this #[cfg(not(feature = "js_embeds"))] block, which discards its arguments and panics. The feature flag exists because embedded formatting pulls in extra formatter dependencies; official Biome binaries ship with it enabled.

Source

Thrown at crates/biome_service/src/file_handlers/javascript.rs:1800

        formatted.propagate_expand();

        match formatted.print() {
            Ok(printed) => Ok(printed),
            Err(error) => Err(WorkspaceError::FormatError(error.into())),
        }
    }

    #[cfg(not(feature = "js_embeds"))]
    {
        let _ = (
            biome_path,
            document_file_source,
            parse,
            settings,
            embedded_nodes,
            workspace_db,
        );
        panic!("formatting embedded JavaScript snippets requires the `js_embeds` feature")
    }
}

pub(crate) fn pull_diagnostics_and_actions(
    params: DiagnosticsAndActionsParams,
) -> PullDiagnosticsAndActionsResult {
    let DiagnosticsAndActionsParams {
        parsed_source,
        settings,
        language,
        path,
        only,
        skip,
        categories,
        workspace_db,
        project_layout,
        suppression_reason,
        enabled_selectors,

View on GitHub (pinned to 0fca643d22)

Solutions

1. Enable the feature: depend on biome_service with features = ["js_embeds"] (or default features) and rebuild
2. If embedded formatting is not needed, disable it at the configuration level so format_embedded is never called with snippets (avoid formatting files containing embedded CSS/GraphQL)
3. Check cargo tree -e features biome_service to confirm who is disabling the feature before blaming your own manifest

Example fix

# before
biome_service = { path = "../biome_service", default-features = false }

# after
biome_service = { path = "../biome_service", default-features = false, features = ["js_embeds"] }

# Cargo.toml - declare the feature explicitly
biome_service = { path = "../biome_service", features = ["js_embeds"] }

# tests/smoke.rs - fail fast if the feature is off in your build
#[test]
fn js_embeds_feature_is_enabled() {
    let formatted = format_js_with_embed("const s = css`color: red;`");
    assert!(formatted.is_ok(), "biome_service was built without js_embeds");
}

When it happens

Trigger: A downstream crate builds biome_service with the js_embeds feature off (e.g. default-features = false) and then formats a JS-family document whose parse contains embedded nodes, invoking format_embedded (javascript.rs:1691) with a non-empty snippet set.

Common situations: Custom tooling that embeds biome_service and trims features for compile time/binary size; feature unification accidentally disabling defaults (another dependency pulling biome_service with default-features = false); building only parts of the workspace (cargo build -p) without the workspace's full feature set.

Related errors

• token kind {kind:?} cannot be transformed to text
• empty file
• found a token with no parent
• empty file
• found a token with no parent

AI-assisted analysis of biomejs/biome@0fca643d22 (2026-08-20). Data as JSON: /api/errors/a47e3582cebeef25. Report an issue: GitHub.