affaan-m/ECC · error · anyhow::Error

invalid cron expression `{trimmed}`: expected 5, 6, or 7 fie

Error message

invalid cron expression `{trimmed}`: expected 5, 6, or 7 fields but found {fields}

What it means

The parse_cron_schedule function normalizes cron expressions before passing them to CronSchedule::from_str. It expects exactly 5, 6, or 7 whitespace-separated fields. Five-field expressions (traditional Unix cron) get a '0 ' prefix for seconds. Anything else is rejected as malformed.

Source

Thrown at ecc2/src/session/manager.rs:2365

}

fn resolve_session(db: &StateStore, id: &str) -> Result<Session> {
    let session = if id == "latest" {
        db.get_latest_session()?
    } else {
        db.get_session(id)?
    };

    session.ok_or_else(|| anyhow::anyhow!("Session not found: {id}"))
}

fn parse_cron_schedule(expr: &str) -> Result<CronSchedule> {
    let trimmed = expr.trim();
    let normalized = match trimmed.split_whitespace().count() {
        5 => format!("0 {trimmed}"),
        6 | 7 => trimmed.to_string(),
        fields => {
            anyhow::bail!(
                "invalid cron expression `{trimmed}`: expected 5, 6, or 7 fields but found {fields}"
            )
        }
    };
    CronSchedule::from_str(&normalized)
        .with_context(|| format!("invalid cron expression `{trimmed}`"))
}

fn next_schedule_run_at(
    expr: &str,
    after: chrono::DateTime<chrono::Utc>,
) -> Result<chrono::DateTime<chrono::Utc>> {
    parse_cron_schedule(expr)?
        .after(&after)
        .next()
        .map(|value| value.with_timezone(&chrono::Utc))
        .ok_or_else(|| anyhow::anyhow!("cron expression `{expr}` did not yield a future run time"))
}

View on GitHub (pinned to 01e15490f0)

Solutions

Ensure the cron expression has exactly 5 fields (min hour day month weekday), 6 (with seconds), or 7 (with seconds and years)
Trim and validate the expression's field count before scheduling
Check for accidental double-spaces or tabs that split_whitespace would count as extra fields
Use a cron expression validator or linter in config tooling

Example fix

// before
let schedule = parse_cron_schedule("0 9 * *")?;

// after
let schedule = parse_cron_schedule("0 9 * * *")?;  // 5 fields: min hour day month weekday

Defensive patterns

Strategy: validation

Validate before calling

fn validate_cron_fields(expr: &str) -> Result<()> {
    let count = expr.trim().split_whitespace().count();
    match count {
        5 | 6 | 7 => Ok(()),
        n => Err(anyhow!("cron expression must have 5, 6, or 7 fields, found {n}")),
    }
}

Type guard

fn is_valid_cron_field_count(expr: &str) -> bool {
    matches!(expr.trim().split_whitespace().count(), 5 | 6 | 7)
}

Prevention

Validate cron expressions at config-load time rather than at first scheduling
Use cron expression linters or validators in configuration tooling
Document the expected field count for your cron dialect in config templates

When it happens

Trigger: Passing a cron expression to parse_cron_schedule or next_schedule_run_at that does not have exactly 5, 6, or 7 whitespace-separated fields.

Common situations: Typo in schedule config (e.g., extra spaces counted as fields, missing field). Using a non-standard cron dialect. Copy-paste error from documentation that uses dashes instead of spaces. Empty schedule string.

Related errors

AI-assisted analysis of affaan-m/ECC@01e15490f0 (2026-08-13). Data as JSON: /api/errors/33bd0387c52d7a96. Report an issue: GitHub.