dbt-labs/dbt-core · error · InvalidOperation

set() requires 1 argument

Error message

set() requires 1 argument

What it means

set() converts a list (or other iterable) into a dbt set with unique values. The implementation accepts 1 or 2 positional arguments; zero arguments or more than two triggers this InvalidOperation error. It guards the arity before the ArgParser processes the iterable.

Source

Thrown at crates/dbt-jinja-utils/src/functions/base.rs:688

/// Convert any iterable to a set with unique elements.
///
/// Args:
///     value: An iterable value to convert to a set (required)
///     default: (optional) Value to return if conversion fails (can be passed
///              as second positional argument or kwarg: default="...")
///
/// Example:
/// ```jinja
/// {% set my_list = [1, 2, 2, 3] %}
/// {% set unique_values = set(my_list) %}
/// -- Returns set with {1, 2, 3}
/// {% set empty = set([]) %}
/// -- Returns empty set
/// ```
pub fn set_fn() -> impl Fn(&[Value], Kwargs) -> Result<Value, Error> {
    move |args: &[Value], kwargs: Kwargs| -> Result<Value, Error> {
        if args.is_empty() || args.len() > 2 {
            return Err(Error::new(
                ErrorKind::InvalidOperation,
                "set() requires 1 argument",
            ));
        }

        let mut arg_parser = ArgParser::new(args, Some(kwargs));
        let value = arg_parser.get::<Value>("value")?;
        let default = arg_parser.get_optional::<Value>("default");

        match value.try_iter() {
            Ok(iter) => Ok(Value::from_object(iter.collect::<MutableSet>())),
            Err(_) => match default {
                Some(def) => Ok(def),
                None => Ok(Value::from(())),
            },
        }
    }
}

View on GitHub (pinned to 0267ce9170)

Solutions

1. Pass exactly one list argument: set(my_list)
2. For an empty set use set([]) instead of set()
3. Remove any extra positional arguments beyond the iterable (kwargs like fillvalue may be fine for zip but check the set API)

Example fix

// before
{% set s = set() %}
// after
{% set s = set([]) %}

{% if my_list is not sequence %}
  {{ exceptions.raise_compiler_error('set() expects a list in ' ~ this) }}
{% endif %}
{% set s = set(my_list) %}

{% macro is_settable(x) %}{{ return(x is defined and x is sequence) }}{% endmacro %}

When it happens

Trigger: Calling set() with no arguments, or set(a, b, c) with three or more positional arguments. Note set(a, b) is allowed (two args), only 0 or 3+ are rejected despite the message saying 'requires 1 argument'.

Common situations: Porting Python habits like set() for an empty set into Jinja where that arity is invalid; accidentally leaving a trailing comma or spread that adds extra positional args; converting Python code that used set literals incorrectly.

Understand the failure class

Background: "missing required argument" and "the following required arguments were not provided": what required-argument errors mean and how to fix them — this error's family across 20 libraries.

Related errors

• diff_of_two_dicts requires exactly 2 arguments
• render requires exactly one argument (the string to render)
• set_strict requires exactly 1 argument
• zip requires at least 1 argument
• has_var requires 1 argument

AI-assisted analysis of dbt-labs/dbt-core@0267ce9170 (2026-09-07). Data as JSON: /api/errors/a05068c3611192bb. Report an issue: GitHub.