nautechsystems/nautilus_trader · error · ValueError

Chart name cannot be empty

Error message

Chart name cannot be empty

What it means

A password and/or app key was supplied but no username, so BetfairCredential::resolve rejects the incomplete triple before any login attempt. As with other partial states, providing any field in config disables the environment fallback, which commonly triggers this when the username lives only in the environment but the password is set in config.

Source

Thrown at python/nautilus_trader/analysis/tearsheet.py:282

        If name is empty or func is not callable.

    Examples
    --------
    >>> # As a decorator
    >>> @register_chart("my_custom_chart")
    ... def create_custom_chart(returns: pd.Series, **kwargs) -> go.Figure:
    ...     fig = go.Figure()
    ...     # ... custom visualization logic
    ...     return fig
    >>>
    >>> # Or called directly
    >>> register_chart("another_chart", create_custom_chart)

    """
    _require_not_none(name, "name")

    if not name.strip():
        raise ValueError("Chart name cannot be empty")

    if func is None:

        def decorator(f: Callable) -> Callable:
            if not callable(f):
                raise ValueError(f"Chart function must be callable, was {type(f)}")
            _CHART_REGISTRY[name] = f
            return f

        return decorator

    if not callable(func):
        raise ValueError(f"Chart function must be callable, was {type(func)}")

    _CHART_REGISTRY[name] = func
    return None

View on GitHub (pinned to a4b06ed870)

Solutions

1. Set the username (config field or BETFAIR_USERNAME)
2. Keep all three credentials in one place - all config or all environment
3. Run a preflight completeness check that lists exactly which of the three are missing

Example fix

// before
.password("secret".into())
.app_key("xxxxxxx".into()) // username assumed from env (never read)

// after
.username("better".into())
.password("secret".into())
.app_key("xxxxxxx".into())

anyhow::ensure!(
    username.is_some() || (password.is_none() && app_key.is_none()),
    "password/app_key provided but username is missing"
);

fn no_credentials_without_username(username: Option<&str>, password: Option<&str>, app_key: Option<&str>) -> bool {
    username.is_some() || (password.is_none() && app_key.is_none())
}

When it happens

Trigger: Config sets password and/or app_key with no username; or the environment has BETFAIR_PASSWORD/BETFAIR_APP_KEY but BETFAIR_USERNAME is unset or typo'd; username key dropped during config migration.

Common situations: Credentials sourced half from a vault and half from env; YAML key renamed from user to username; variable dropped when moving between deployment environments.

Related errors

• {name} must not be None
• height must be positive, was {self.height}
• pandas is required for report generation; install it with `p
• pandas is required for visualization; install it with `pip i
• Chart function must be callable, was {type(f)}

AI-assisted analysis of nautechsystems/nautilus_trader@a4b06ed870 (2026-08-16). Data as JSON: /api/errors/f10d0da3feb6db31. Report an issue: GitHub.