dbt-labs/dbt-core · error

cast() method not implemented for the

Error message

cast() method not implemented for the {} data type

What it means

This DataTypeRepr implementation leaves cast() unimplemented, so any cast attempt — directly or via test(), which just wraps cast().is_ok() — fails for this data type. It marks type coercions the agate port has not yet provided.

Solutions

1. Implement cast for this data type, or route the coercion through the string representation as a fallback
2. Return a distinguishable Err so callers can treat it as 'cannot cast' rather than a crash
3. Register a text-mediated fallback cast for unimplemented types

When it happens

Trigger: Thrown at crates/dbt-agate/src/data_type.rs:69 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of dbt-labs/dbt-core@0267ce9170 (2026-09-07). Data as JSON: /api/errors/17527e6482a66699. Report an issue: GitHub.

Appendix: source

Thrown at crates/dbt-agate/src/data_type.rs:69

pub trait DataTypeRepr: fmt::Debug + Send + Sync {
    /// A sequence of values which should be cast to [None] when encountered by this data type.
    fn null_values(&self) -> &NullValues<'static>;

    /// The name of the [DataType] implementation.
    fn type_name(&self) -> &str;

    /// Test, for purposes of type inference, if a value could possibly be
    /// coerced to this data type.
    ///
    /// This is really just a thin wrapper around :meth:`DataType.cast`.
    fn test(&self, d: &dyn DataTypeRepr) -> bool {
        self.cast(d).is_ok()
    }

    /// Coerce a given string value into this column's data type.
    fn cast(&self, d: &dyn DataTypeRepr) -> Result<Value, Error> {
        // raise NotImplementedError
        let err = Error::new(
            ErrorKind::InvalidOperation,
            format!(
                "cast() method not implemented for the {} data type",
                d.type_name()
            ),
        );
        Err(err)
    }

    /// Format a given native value for CSV serialization.
    fn csvify(&self, d: &Value) -> Value {
        if d.is_none() || d.is_undefined() {
            Value::from(())
        } else {
            Value::from(d.to_string())
        }
    }

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