reflex-dev/reflex · error · ValueError

The condition must be set.

Error message

The condition must be set.

What it means

`rx.cond(condition, c1, c2)` needs a condition that can be converted into a Var. `LiteralVar.create(condition)` returning None means the condition is None or of a type Reflex cannot render as a literal — so there is nothing to branch on.

Source

Thrown at packages/reflex-components-core/src/reflex_components_core/core/cond.py:190

def cond(condition: Any, c1: Any, c2: Any = types.Unset(), /) -> Component | Var:
    """Create a conditional component or Prop.

    Args:
        condition: The cond to determine which component to render.
        c1: The component or prop to render if the cond_var is true.
        c2: The component or prop to render if the cond_var is false.

    Returns:
        The conditional component.

    Raises:
        ValueError: If the arguments are invalid.
    """
    # Convert the condition to a Var.
    cond_var = LiteralVar.create(condition)
    if cond_var is None:
        msg = "The condition must be set."
        raise ValueError(msg)

    # If the first component is a component, create a Cond component.
    if isinstance(c1, BaseComponent):
        if not isinstance(c2, types.Unset) and not isinstance(c2, BaseComponent):
            return Cond.create(cond_var.bool(), c1, Fragment.create(c2))
        return Cond.create(cond_var.bool(), c1, c2)

    # Otherwise, create a conditional Var.
    # Check that the second argument is valid.
    if isinstance(c2, BaseComponent):
        return Cond.create(cond_var.bool(), Fragment.create(c1), c2)
    if isinstance(c2, types.Unset):
        msg = "For conditional vars, the second argument must be set."
        raise ValueError(msg)

    # convert the truth and false cond parts into vars so the _var_data can be obtained.
    c1_var = Var.create(c1)
    c2_var = Var.create(c2)

View on GitHub (pinned to 45b8ed5ab7)

Solutions

1. Pass a real boolean expression or State Var: rx.cond(State.is_logged_in, ...)
2. Default None conditions: rx.cond(condition if condition is not None else False, ...)
3. Ensure the condition is a supported type (bool, int, str, Var, comparison result)

Example fix

// before
rx.cond(State.user, greeting, login_form)  # user is None or unsupported type
// after
rx.cond(State.user is not None, greeting, login_form)

if condition is None:
    condition = False
comp = rx.cond(condition, c1, c2)

def is_condable(c) -> bool:
    return c is not None and (isinstance(c, (bool, int, float, str, Var)) or hasattr(c, '_var_type') or callable(getattr(c, '__eq__', None)))

When it happens

Trigger: `rx.cond(None, a, b)`, `rx.cond(untyped_object, ...)`, or passing a value whose type LiteralVar.create does not handle.

Common situations: Conditionally building UI where the condition variable was never initialized; passing a Python object (dict/dataclass) instead of a bool, comparison, or Var; refactoring leaves the condition expression empty.

Related errors

• Var-returning `@rx.memo` `{func_name}` cannot depend on embe
• Invalid prop(s) {invalid_fields_str} for {component_name!r}.
• default_color_mode must be one of {allowed_color_modes}, but
• Invalid event chain: {value!s} of type {value._var_type}
• Invalid event: {v}

AI-assisted analysis of reflex-dev/reflex@45b8ed5ab7 (2026-08-28). Data as JSON: /api/errors/d334a263cfebf09e. Report an issue: GitHub.