infiniflow/ragflow · error · listOpPanic

ListOperations: nth requires n to be within the valid range

Error message

ListOperations: nth requires n to be within the valid range in strict mode, got %d

What it means

opNth panics in strict mode when n == 0. Indexing semantics are 1-indexed for positive n and -N counts from the end, so 0 selects nothing; strict mode (l.param.Strict) treats that as a caller bug and panics via strictRangePanic instead of returning an empty list (the non-strict behavior).

Source

Thrown at internal/agent/component/list_operations.go:386

	}
}

// Outputs returns the transformed list plus head/tail scalars.
func (l *ListOperationsComponent) Outputs() map[string]string {
	return map[string]string{
		"result": "Transformed list (per the configured operation).",
		"first":  "First element of the result (nil for empty result).",
		"last":   "Last element of the result (nil for empty result).",
	}
}

// opNth: 1-indexed for positive n, -N (from end) for negative n.
// n=0 → empty (or error in strict mode).
func (l *ListOperationsComponent) opNth(items []any) []any {
	n := l.param.N
	if n == 0 {
		if l.param.Strict {
			panic(strictRangePanic("nth", n))
		}
		return []any{}
	}
	if n > 0 {
		if n <= len(items) {
			return []any{items[n-1]}
		}
		if l.param.Strict {
			panic(strictRangePanic("nth", n))
		}
		return []any{}
	}
	absN := -n
	if absN <= len(items) {
		return []any{items[n]}
	}
	if l.param.Strict {
		panic(strictRangePanic("nth", n))

View on GitHub (pinned to 554fb1133a)

Solutions

1. Set N to a non-zero value: >= 1 for 1-indexed from the start, or negative (e.g. -1 for last element)
2. If N comes from an upstream node, add a guard/branch so it is never 0 when strict mode is on
3. If an empty result for n=0 is acceptable, disable strict mode (Strict: false) to get the lenient []any{} return

Example fix

# before
operation: nth
strict: true
n: 0        # panic: nth requires n to be within the valid range

# after
operation: nth
strict: true
n: 1        # first element

if op == "nth" && strict && n == 0 {
    return fmt.Errorf("nth with strict=true requires non-zero n")
}

When it happens

Trigger: Running a ListOperations component with operation nth, Strict: true, and N set to 0 on any input list.

Common situations: N is wired to an upstream output that evaluates to 0 (e.g. a computed index or a default value), or a template field left at its zero default while strict mode was enabled to catch bad indices.

Related errors

• ListOperations: head requires n to be within the valid range
• ListOperations: tail requires n to be within the valid range
• {operation} requires n to be within the valid range in stric
• failed to initialize logger: {err}
• Invoke: invalid proxy URL %q: %v

AI-assisted analysis of infiniflow/ragflow@554fb1133a (2026-08-15). Data as JSON: /api/errors/0af07414f38949a0. Report an issue: GitHub.