hasura/graphql-engine · error · ScalarBooleanExpressionTypeError

cannot find type {custom_type:} when resolving arguments for

Error message

cannot find type {custom_type:} when resolving arguments for comparison operator {operator_name:} for {boolean_expression_type:}

What it means

A comparison operator on a boolean expression type declares an argument whose type is a custom type that cannot be found during resolution. The resolver needs the argument's type to build the operator's input schema; a missing Qualified<CustomTypeName> aborts the scalar boolean expressions stage.

Source

Thrown at v3/crates/metadata-resolve/src/stages/scalar_boolean_expressions/error.rs:25

    data_connector::{DataConnectorName, DataConnectorScalarType},
    types::{CustomTypeName, OperatorName},
};

#[derive(Debug, thiserror::Error)]
pub enum ScalarBooleanExpressionTypeError {
    #[error(
        "unknown data connector {data_connector:} referenced in scalar type representation of {scalar_type:}"
    )]
    ScalarTypeFromUnknownDataConnector {
        data_connector: Qualified<DataConnectorName>,
        scalar_type: DataConnectorScalarType,
    },
    #[error("cannot find scalar type {scalar_type:} in data connector {data_connector:}")]
    UnknownScalarTypeInDataConnector {
        data_connector: Qualified<DataConnectorName>,
        scalar_type: DataConnectorScalarType,
    },
    #[error(
        "cannot find type {custom_type:} when resolving arguments for comparison operator {operator_name:} for {boolean_expression_type:}"
    )]
    UnknownCustomTypeInComparisonOperatorArgument {
        custom_type: Qualified<CustomTypeName>,
        operator_name: OperatorName,
        boolean_expression_type: Qualified<CustomTypeName>,
    },
    #[error("data connector {data_connector:} could not be found")]
    DataConnectorNotFound {
        data_connector: Qualified<DataConnectorName>,
    },
    #[error("scalar representations for data connector {data_connector:} could not be found")]
    DataConnectorScalarRepresentationsNotFound {
        data_connector: Qualified<DataConnectorName>,
    },
    #[error(
        "scalar type representation required for type {scalar_type:} in data connector {data_connector:}"
    )]

View on GitHub (pinned to 724551b9ae)

Solutions

Grep metadata for the custom type name from the error and correct the spelling or namespace in the operator's argument definition
If the type was renamed, update the operator argument to the new name
If the type is missing entirely, add its definition or use a builtin scalar for the argument

Example fix

# before
operators:
  _eq:
    argumentType: my_subgraph/Teimstamp   # type is 'my_subgraph/Timestamp'
# after
operators:
  _eq:
    argumentType: my_subgraph/Timestamp

Defensive patterns

Strategy: validation

Validate before calling

fn check_operator_arg_types(
    types: &BTreeSet<Qualified<CustomTypeName>>,
    ops: &[(OperatorName, Qualified<CustomTypeName>)],
) -> Result<(), String> {
    for (op, ty) in ops {
        if !types.contains(ty) { return Err(format!("operator {op} argument type {ty} undefined")); }
    }
    Ok(())
}

Try / catch

downcast UnknownCustomTypeInComparisonOperatorArgument and report operator name, missing type, and enclosing boolean expression type

Prevention

Grep for a custom type name before renaming/removing it
Keep operator definitions and the types they reference in the same subgraph

When it happens

Trigger: An operator in a boolean expression type configuration lists an argument referencing a custom type name that isn't defined in the types subgraph — typo, deleted type, or wrong namespace qualification.

Common situations: Renaming or removing a custom type still used as an operator argument; copy-pasting operator definitions between subgraphs with different type sets; namespace mismatch in the qualified type name.

Related errors

AI-assisted analysis of hasura/graphql-engine@724551b9ae (2026-08-28). Data as JSON: /api/errors/bea8c54aa73e2307. Report an issue: GitHub.