n8n-io/n8n · error · ExpressionExtensionError

expected two arguments (value, defaultValue) for this functi

Error message

expected two arguments (value, defaultValue) for this function

What it means

`ifEmpty(value, defaultValue)` requires exactly two arguments; the body checks `arguments.length !== 2` and throws if it is not. The runtime shim cannot fall back because the whole point of the function is to supply a default.

Source

Thrown at packages/@n8n/expression-runtime/src/extensions/function-extensions.ts:51

	}
	return result;
};

const average = (...args: number[]) => {
	return aAverage(args);
};

const not = (value: unknown): boolean => {
	return !value;
};

function ifEmpty<T, V>(value: V, defaultValue: T) {
	if (arguments.length !== 2) {
		// DIVERGENCE from packages/workflow/src/extensions/extended-functions.ts:
		// The original throws ExpressionError (from ExecutionBaseError). The runtime
		// uses ExpressionExtensionError because the full ExpressionError class is not
		// available in the extensions layer — only a minimal shim exists in safe-globals.
		throw new ExpressionExtensionError(
			'expected two arguments (value, defaultValue) for this function',
		);
	}
	if (value === undefined || value === null || value === '') {
		return defaultValue;
	}
	if (typeof value === 'object') {
		if (Array.isArray(value) && !value.length) {
			return defaultValue;
		}
		if (!Object.keys(value).length) {
			return defaultValue;
		}
	}
	return value;
}

ifEmpty.doc = {

View on GitHub (pinned to 5ac6606e81)

Solutions

Always pass a default value: `.ifEmpty('N/A')`.
Double-check the expression has both operands inside the parentheses.
If emptiness is acceptable, omit `.ifEmpty()` entirely rather than calling it half-formed.

Example fix

// before
{{ $json.note.ifEmpty() }}
// after
{{ $json.note.ifEmpty('N/A') }}

Defensive patterns

Strategy: validation

Validate before calling

// Ensure both operands are present before constructing the expression:
if ($json.value === undefined || $json.fallback === undefined) {
  throw new Error('ifEmpty(): both value and defaultValue are required');
}
return $json;

Prevention

Always pass a default: `.ifEmpty('N/A')`.
Double-check both operands are inside the parentheses.
If emptiness is acceptable, simply omit the call.

When it happens

Trigger: Calling `.ifEmpty()` with no default, or with only one argument; using `.ifEmpty` as a bare property reference instead of a call.

Common situations: Forgot to provide the fallback value; copied a pattern from a language where the default is optional; field renamed so the argument expression resolved to nothing.

Related errors

AI-assisted analysis of n8n-io/n8n@5ac6606e81 (2026-08-12). Data as JSON: /api/errors/551c8ebab84aec62. Report an issue: GitHub.