netdata/netdata · error · anyhow::Error

{name}() expects exactly 1 argument

Error message

{name}() expects exactly 1 argument

What it means

A one-argument value function (via `one_arg`) received a different number of arguments — the parser checks `args.len() != 1` before parsing the single argument. Applies to functions like SetName/ClassifyRole targets where exactly one value expression is allowed.

Source

Thrown at src/crates/netflow-plugin/src/enrichment/classifiers/parse/value.rs:6

use super::split::*;
use super::*;

pub(super) fn one_arg(name: &str, args: &[String]) -> Result<ValueExpr> {
    if args.len() != 1 {
        anyhow::bail!("{name}() expects exactly 1 argument");
    }
    parse_value_expr(args[0].trim())
}

fn three_args(name: &str, args: &[String]) -> Result<(ValueExpr, ValueExpr, ValueExpr)> {
    if args.len() != 3 {
        anyhow::bail!("{name}() expects exactly 3 arguments");
    }
    Ok((
        parse_value_expr(args[0].trim())?,
        parse_value_expr(args[1].trim())?,
        parse_value_expr(args[2].trim())?,
    ))
}

pub(super) fn one_string_arg(name: &str, args: &[String]) -> Result<ValueExpr> {
    let value = one_arg(name, args)?;
    if !value.is_string_expression() {

View on GitHub (pinned to 4864de85e2)

Solutions

1. Provide exactly one argument.
2. To combine values, use one concatenated expression: `SetName(Format("{}-{}", A, B))` or `SetName(A + B)`.

Example fix

// before
SetName(DstIP, SrcIP)

// after
SetName(DstIP + "/" + SrcIP)

fn arity_ok(name: &str, args: &[String]) -> bool {
    if matches!(name, "SetName" | "SetDescription" | "ClassifyRole" | "ClassifySite" | "Classify" | "ClassifyGroup") {
        return args.len() == 1;
    }
    true
}

When it happens

Trigger: Calling a 1-arg function with zero or multiple arguments: `SetName()`, `SetName(a, b)`, `ClassifyRole()`.

Common situations: Expecting SetName to accept multiple concatenated values instead of using `+` concatenation; forgetting the argument entirely.

Related errors

• Reject() does not accept arguments
• ClassifyExternal() does not accept arguments
• ClassifyInternal() does not accept arguments
• {name}() expects exactly 3 arguments
• Format() expects at least one argument

AI-assisted analysis of netdata/netdata@4864de85e2 (2026-08-15). Data as JSON: /api/errors/8de79734ef1af7fe. Report an issue: GitHub.