reflex-dev/reflex · error · ValueError

Annotation of the computed var assigned to the data field sh

Error message

Annotation of the computed var assigned to the data field should be provided.

What it means

data_table needs the Python type of data to serialize pandas DataFrames correctly. If data is a computed var annotated as Any (no return annotation), Reflex cannot tell whether it is a DataFrame.

Source

Thrown at packages/reflex-components-gridjs/src/reflex_components_gridjs/datatable.py:68

        Args:
            *children: The children of the component.
            **props: The props to pass to the component.

        Returns:
            The datatable component.

        Raises:
            ValueError: If a pandas dataframe is passed in and columns are also provided.
        """
        data = props.get("data")
        columns = props.get("columns")

        # The annotation should be provided if data is a computed var. We need this to know how to
        # render pandas dataframes.
        if is_computed_var(data) and data._var_type == Any:
            msg = "Annotation of the computed var assigned to the data field should be provided."
            raise ValueError(msg)

        if (
            columns is not None
            and is_computed_var(columns)
            and columns._var_type == Any
        ):
            msg = "Annotation of the computed var assigned to the column field should be provided."
            raise ValueError(msg)

        # If data is a pandas dataframe and columns are provided throw an error.
        if (
            types.is_dataframe(type(data))
            or (isinstance(data, Var) and types.is_dataframe(data._var_type))
        ) and columns is not None:
            msg = "Cannot pass in both a pandas dataframe and columns to the data_table component."
            raise ValueError(msg)

        # If data is a list and columns are not provided, throw an error

View on GitHub (pinned to 45b8ed5ab7)

Solutions

1. Annotate the computed var: @rx.var def get_data(self) -> pd.DataFrame: ...
2. Or annotate as the concrete list type you return

Example fix

# before
@rx.var
def table_data(self):
    return self.df
# after
@rx.var
def table_data(self) -> pd.DataFrame:
    return self.df

import inspect
ret = inspect.signature(get_data.fn if hasattr(get_data, 'fn') else get_data).return_annotation
assert ret is not inspect.Signature.empty, 'annotate the computed var feeding data_table'

def computed_var_is_annotated(v: Any) -> bool:
    return not (is_computed_var(v) and v._var_type is Any)

When it happens

Trigger: @rx.var-def computed var without a return annotation passed to rx.data_table(data=...) — data._var_type is Any.

Common situations: Writing @rx.var def get_data(self): return self.df without an annotation, often after refactoring or in dynamically-typed codebases.

Related errors

• Annotation of the computed var assigned to the column field
• UntypedComputedVarError(var_name=fget.__name__)
• `@rx.memo` on `{fn.__name__}` must return `rx.Component` or
• `{handler_name}` handler should have a parameter annotated a
• MissingAnnotationError

AI-assisted analysis of reflex-dev/reflex@45b8ed5ab7 (2026-08-28). Data as JSON: /api/errors/328c9c404db65682. Report an issue: GitHub.