reflex-dev/reflex · error · TypeError

The _var_is_local argument is not supported for Var.

Error message

The _var_is_local argument is not supported for Var.

What it means

Var._replace rejects the legacy keyword _var_is_local. Modern Var tracks locality inside VarData, so the old boolean flag is no longer accepted; passing it raises TypeError. The same guard covers _var_is_string and _var_full_name_needs_state_prefix.

Source

Thrown at packages/reflex-base/src/reflex_base/vars/base.py:787

        merge_var_data: VarData | None = None,
        **kwargs: Any,
    ) -> Self | Var:
        """Make a copy of this Var with updated fields.

        Args:
            _var_type: The new type of the Var.
            merge_var_data: VarData to merge into the existing VarData.
            **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:

View on GitHub (pinned to 45b8ed5ab7)

Solutions

1. Remove the _var_is_local kwarg and set locality via VarData (e.g. pass a VarData with the appropriate hooks) or use the replacement public API
2. Update the calling code to the current _replace signature (only _var_type/_var_data and friends)
3. Upgrade any third-party reflex packages pinned to old versions so they stop passing the flag
4. Search the codebase for _var_is_local and migrate every occurrence

Example fix

# before
v = v._replace(_var_is_local=True)
# after
from reflex.vars import VarData
v = v._replace(_var_data=VarData(...))  # locality now lives in VarData

kwargs.pop('_var_is_local', None)  # legacy kwarg, no longer supported
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_is_local=True) or dataclasses.replace-style updates with that kwarg; code written against an older reflex API where these flags existed on Var; copy-pasted internal framework code after an upgrade.

Common situations: Upgrading reflex to a version where Var internals were refactored to VarData; long-lived projects or component libraries using _replace with legacy kwargs; tutorials predating the refactor.

Related errors

• The _var_is_string argument is not supported for Var.
• The _var_full_name_needs_state_prefix argument is not suppor
• 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/7d46f19dca9aca54. Report an issue: GitHub.