biomejs/biome · error

empty file

Error message

empty file

What it means

Panic in the JavaScript format-on-type handler (javascript.rs:1638). For a textDocument/onTypeFormatted request, Biome resolves the token under the cursor with tree.token_at_offset(offset); TokenAtOffset::None means the parsed tree contains no tokens, i.e. the document is empty. Despite the 'File is empty, do nothing' comment, the arm panics, so on-type formatting an empty JS/TS/JSX document crashes this path.

Source

Thrown at crates/biome_service/src/file_handlers/javascript.rs:1673

    settings: &SettingsWithEditor,
    offset: TextSize,
    workspace_db: WorkspaceDb,
) -> Result<Printed, WorkspaceError> {
    let options = resolve_format_options(path, document_file_source, settings, &workspace_db);
    debug!("{:?}", &options);
    let tree = parse.syntax(&workspace_db);

    let range = tree.text_range_with_trivia();
    if offset < range.start() || offset > range.end() {
        return Err(WorkspaceError::FormatError(FormatError::RangeError {
            input: TextRange::at(offset, TextSize::from(0)),
            tree: range,
        }));
    }

    let token = match tree.token_at_offset(offset) {
        // File is empty, do nothing
        TokenAtOffset::None => panic!("empty file"),
        TokenAtOffset::Single(token) => token,
        // The cursor should be right after the closing character that was just typed,
        // select the previous token as the correct one
        TokenAtOffset::Between(token, _) => token,
    };

    if token.text_trimmed_range().end() != offset {
        return Ok(format_on_type_noop(offset));
    }

    if !matches_on_type_char(token.text_trimmed()) {
        return Ok(format_on_type_noop(offset));
    }

    let root_node = match token.parent() {
        Some(node) => node,
        None => panic!("found a token with no parent"),
    };

View on GitHub (pinned to 0fca643d22)

Solutions

1. Update Biome - check release notes for a fix and report at https://github.com/biomejs/biome/issues if still present
2. Client-side guard: only send textDocument/onTypeFormatted when document.getText().length > 0
3. In a fork: TokenAtOffset::None => return Ok(format_on_type_noop(offset))

Example fix

// before
TokenAtOffset::None => panic!("empty file"),

// after
TokenAtOffset::None => return Ok(format_on_type_noop(offset)),

// LSP client (TypeScript) - skip on-type formatting for empty JS/TS files
if (document.getText().length === 0) return; // avoid the server-side panic path

const isEmptyDocument = (document: TextDocument): boolean =>
  document.getText().length === 0;

When it happens

Trigger: An LSP client sends onTypeFormatted for a zero-length .js/.ts/.jsx file: offset 0 passes the range guard over tree range 0..0, token_at_offset(0) returns None, and the panic fires. Any non-empty file returns at least a token and avoids this arm.

Common situations: The most-hit variant of this bug since JS files dominate Biome usage: editors firing on-type format on empty buffers (new untitled files, cleared documents), aggressive format-on-key plugins, or LSP test harnesses.

Related errors

• empty file
• empty file
• empty file
• empty file
• found a token with no parent

AI-assisted analysis of biomejs/biome@0fca643d22 (2026-08-20). Data as JSON: /api/errors/eaa7267d71c6b2b9. Report an issue: GitHub.