reflex-dev/reflex · error · TypeError

The _var_full_name_needs_state_prefix argument is not suppor

Error message

The _var_full_name_needs_state_prefix argument is not supported for Var.

What it means

Var._replace rejects the legacy keyword _var_full_name_needs_state_prefix. Whether a Var's full name is prefixed with its owning state is now derived from VarData (the state field), so the old boolean flag raises TypeError. Same family as the _var_is_local/_var_is_string guards.

Source

Thrown at packages/reflex-base/src/reflex_base/vars/base.py:795

            **kwargs: Var fields to update.

        Returns:
            A new Var with the updated fields overwriting the corresponding fields in this Var.

        Raises:
            TypeError: If _var_is_local, _var_is_string, or _var_full_name_needs_state_prefix is not None.
        """
        if kwargs.get("_var_is_local", False) is not False:
            msg = "The _var_is_local argument is not supported for Var."
            raise TypeError(msg)

        if kwargs.get("_var_is_string", False) is not False:
            msg = "The _var_is_string argument is not supported for Var."
            raise TypeError(msg)

        if kwargs.get("_var_full_name_needs_state_prefix", False) is not False:
            msg = "The _var_full_name_needs_state_prefix argument is not supported for Var."
            raise TypeError(msg)
        value_with_replaced = dataclasses.replace(
            self,
            _var_type=_var_type or self._var_type,
            _var_data=VarData.merge(
                kwargs.get("_var_data", self._var_data), merge_var_data
            ),
            **kwargs,
        )

        if (js_expr := kwargs.get("_js_expr")) is not None:
            object.__setattr__(value_with_replaced, "_js_expr", js_expr)

        return value_with_replaced

    @overload
    @classmethod
    def create(  # pyright: ignore[reportOverlappingOverload]
        cls,

View on GitHub (pinned to 45b8ed5ab7)

Solutions

1. Remove the kwarg — attach the owning state through VarData instead (VarData(state=...) via the state's var path)
2. Use the public helpers that create properly-prefixed vars (State.var_name or Var operations on state attributes)
3. Upgrade third-party packages pinned to old reflex versions
4. Grep for _var_full_name_needs_state_prefix and migrate every site

Example fix

# before
v = v._replace(_var_full_name_needs_state_prefix=True)
# after
v = VarData.merge(v._var_data, VarData(state=State)).apply(v)  # prefixing comes from VarData.state

kwargs.pop('_var_full_name_needs_state_prefix', None)
v = v._replace(**kwargs)

def is_supported_replace_kwarg(name: str) -> bool:
    return name not in {'_var_is_local', '_var_is_string', '_var_full_name_needs_state_prefix'}

When it happens

Trigger: Calling var._replace(_var_full_name_needs_state_prefix=True); internal-style code from older reflex versions; libraries that manipulated state-prefixing via this private flag.

Common situations: Upgrading reflex after the VarData refactor; maintaining a fork or component library using private Var internals; porting old compiler code.

Related errors

• The _var_is_local argument is not supported for Var.
• The _var_is_string argument is not supported for Var.
• Expected _js_expr to be a string, got value {self._js_expr!r
• Unsupported type {var_type} for guess_type.
• Var of type {self._var_type} does not support item access.

AI-assisted analysis of reflex-dev/reflex@45b8ed5ab7 (2026-08-28). Data as JSON: /api/errors/29c7b34c6dee2602. Report an issue: GitHub.