paperclipai/paperclip · error · Error

Empty element in cron ${spec.name} field

Error message

Empty element in cron ${spec.name} field

What it means

Token guard in the cron parser's parseField: after splitting a field on commas, one element trims to the empty string (e.g. "1,,5" or a trailing comma). An empty list element cannot denote a value, range, or step, so parsing aborts with the field name (minute/hour/dom/month/dow).

Source

Thrown at server/src/services/cron.ts:79

// Parsing
// ---------------------------------------------------------------------------

/**
 * Parse a single cron field token (e.g. `"5"`, `"1-3"`, `"* /10"`, `"1,3,5"`).
 *
 * @returns Sorted deduplicated array of matching integer values within bounds.
 * @throws {Error} on invalid syntax or out-of-range values.
 */
function parseField(token: string, spec: FieldSpec): number[] {
  const values = new Set<number>();

  // Split on commas first — each part can be a value, range, or step
  const parts = token.split(",");

  for (const part of parts) {
    const trimmed = part.trim();
    if (trimmed === "") {
      throw new Error(`Empty element in cron ${spec.name} field`);
    }

    // Check for step syntax: "X/S" where X is "*" or a range or a number
    const slashIdx = trimmed.indexOf("/");
    if (slashIdx !== -1) {
      const base = trimmed.slice(0, slashIdx);
      const stepStr = trimmed.slice(slashIdx + 1);
      const step = parseInt(stepStr, 10);
      if (isNaN(step) || step <= 0) {
        throw new Error(
          `Invalid step "${stepStr}" in cron ${spec.name} field`,
        );
      }

      let rangeStart = spec.min;
      let rangeEnd = spec.max;

      if (base === "*") {

View on GitHub (pinned to 120ae5428f)

Solutions

1. Remove empty elements (e.g. double commas) from the named cron field.

When it happens

Trigger: Thrown at server/src/services/cron.ts:79 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of paperclipai/paperclip@120ae5428f (2026-08-18). Data as JSON: /api/errors/352526a545bfc979. Report an issue: GitHub.