gnome-shell/js/misc/errorUtils.js

// Common code for displaying errors to the user in various dialogs

function formatSyntaxErrorLocation(error) {
    const {fileName = '<unknown>', lineNumber = 0, columnNumber = 0} = error;
    return ` @ ${fileName}:${lineNumber}:${columnNumber}`;
}

function formatExceptionStack(error) {
    const {stack} = error;
    if (!stack)
        return '\n\n(No stack trace)';

    const indentedStack = stack.split('\n').map(line => `  ${line}`).join('\n');
    return `\n\nStack trace:\n${indentedStack}`;
}

function formatExceptionWithCause(error, seenCauses) {
    let fmt = formatExceptionStack(error);

    const {cause} = error;
    if (!cause)
        return fmt;

    fmt += `\nCaused by: ${cause}`;

    if (cause !== null && typeof cause === 'object') {
        if (seenCauses.has(cause))
            return fmt;  // avoid recursion
        seenCauses.add(cause);

        fmt += formatExceptionWithCause(cause, seenCauses);
    }

    return fmt;
}

/**
 * Formats a thrown exception into a string, including the stack, taking the
 * location where a SyntaxError was thrown into account.
 *
 * @param {Error} error The error to format
 * @returns {string} The formatted string
 */
export function formatError(error) {
    try {
        let fmt = `${error}`;
        if (error === null || typeof error !== 'object')
            return fmt;

        if (error instanceof SyntaxError) {
            fmt += formatSyntaxErrorLocation(error);
            fmt += formatExceptionStack(error);
            return fmt;
        }

        const seenCauses = new Set([error]);
        fmt += formatExceptionWithCause(error, seenCauses);
        return fmt;
    } catch (e) {
        return `(could not display error: ${e})`;
    }
}