Hmbown/CodeWhale · error · anyhow::Error

CRON {field_name} field must not be empty

Error message

CRON {field_name} field must not be empty

What it means

CronField::parse bails when a whole field trims to the empty string. Because ParsedCronExpr::parse splits EXPR with split_whitespace, fields can never be empty on the public path; the guard exists for direct CronField::parse calls (tests, internal callers) with '' or whitespace-only input.

Source

Thrown at crates/tui/src/automation_manager.rs:723

        if valid {
            Ok(())
        } else {
            bail!("CRON EXPR day-of-month/month combination can never occur")
        }
    }
}

#[derive(Debug, Clone)]
struct CronField {
    values: Vec<u32>,
    is_wildcard: bool,
}

impl CronField {
    fn parse(raw: &str, min: u32, max: u32, names: CronNameMap, field_name: &str) -> Result<Self> {
        let trimmed = raw.trim();
        if trimmed.is_empty() {
            bail!("CRON {field_name} field must not be empty");
        }
        let mut values = Vec::new();
        let is_wildcard = trimmed == "*";
        for part in trimmed.split(',') {
            let part = part.trim();
            if part.is_empty() {
                bail!("CRON {field_name} field contains an empty list item");
            }
            let (base, step) = if let Some((base, step)) = part.split_once('/') {
                let step = step
                    .trim()
                    .parse::<u32>()
                    .with_context(|| format!("Failed to parse CRON {field_name} step"))?;
                if step == 0 {
                    bail!("CRON {field_name} step must be >= 1");
                }
                (base.trim(), step)
            } else {

View on GitHub (pinned to 0c42157ee5)

Solutions

1. Treat as an internal invariant: check for empty fields before calling CronField::parse
2. Route all expressions through ParsedCronExpr::parse or parse_rrule
3. Report a bug if this surfaces from a public API entry point

fn has_no_empty_cron_field(expr: &str) -> bool {
    expr.split_whitespace().all(|f| !f.trim().is_empty())
}

When it happens

Trigger: Only reachable by invoking CronField::parse directly with an empty or whitespace-only field string; the public rrule/EXPR path cannot produce an empty field after whitespace splitting.

Common situations: Internal tests or future refactors calling CronField::parse directly; not a user-facing failure mode.

Related errors

• Unsupported RRULE field '{key}' for CRON. Allowed: FREQ,EXPR
• CRON EXPR must have exactly 5 fields: minute hour day-of-mon
• CRON EXPR day-of-month/month combination can never occur
• CRON {field_name} field contains an empty list item
• CRON {field_name} step must be >= 1

AI-assisted analysis of Hmbown/CodeWhale@0c42157ee5 (2026-08-20). Data as JSON: /api/errors/c9fff1ce3361f106. Report an issue: GitHub.