affaan-m/ECC · error · anyhow::Error

invalid cron expression

Error message

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

What it means

parse_cron_schedule validates cron expressions by counting whitespace-separated fields. Standard cron has 5 fields; this parser accepts 5 (prepends a seconds field), 6, or 7. Any other field count is rejected with this message before CronSchedule::from_str is attempted, giving a clearer diagnostic.

Solutions

1. Provide a valid 5-field cron expression, e.g. '0 9 * * *' for daily at 9am
2. Count the fields: minute hour day-of-month month day-of-week (a 6th seconds field or 7th year field is allowed)
3. Replace @daily/@hourly descriptors with equivalent explicit cron expressions
4. Trim stray whitespace and avoid natural-language schedule strings

Example fix

// before
parse_cron_schedule("every day at 9")?;
// after
parse_cron_schedule("0 9 * * *")?; // 5 fields: daily at 09:00

fn is_valid_cron(expr: &str) -> bool {
    let n = expr.trim().split_whitespace().count();
    (5..=7).contains(&n) && !expr.trim().starts_with('@')
}

match parse_cron_schedule(input) {
    Err(e) if e.to_string().contains("expected 5, 6, or 7 fields") => {
        eprintln!("'{input}' is not valid cron; use 5 space-separated fields like '0 9 * * *'");
        Err(e)
    }
    other => other,
}

When it happens

Trigger: Calling schedule creation (which calls parse_cron_schedule) with a string like 'every day' (0 fields), '* * *' (3 fields), or a miscounted expression whose whitespace-separated token count is not 5, 6, or 7.

Common situations: Users pasting natural language ('every morning') instead of cron syntax; forgetting a field ('* * *' instead of '* * * * *'); using descriptors like '@daily' or '@hourly' that split to one token; extra spaces causing miscounts or copy/paste errors.

Understand the failure class

Background: "Invalid ... format", "must be in format X", "does not look like a ..." — invalid argument format errors across CLI tools and libraries — this error's family across 17 libraries.

Related errors

• effect recipe needs at least three scheduled events
• invalid cron expression
• invalid discussion id
• Invalid format: . Use text or json.
• invalid repository

AI-assisted analysis of affaan-m/ECC@8321021c54 (2026-09-16). Data as JSON: /api/errors/33bd0387c52d7a96. Report an issue: GitHub.

Appendix: 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"))
}

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