n8n-io/n8n · error · UnsupportedNodeError

Unsupported syntax: 'Logical operator ${String(node.operator

Error message

Unsupported syntax: 'Logical operator ${String(node.operator)}' is not allowed in SDK code

What it means

The interpreter supports the three JavaScript logical operators: `&&`, `||`, and `??` (nullish coalescing). Since these are the only logical operators in the language, the `default` case at interpreter.ts:676 is effectively unreachable through standard parsing — it exists as a defensive guard for malformed AST nodes or future language extensions.

Source

Thrown at packages/@n8n/workflow-sdk/src/ast-interpreter/interpreter.ts:676

		}
	}

	/**
	 * Visit a logical expression.
	 */
	private visitLogicalExpression(node: ESTree.LogicalExpression): unknown {
		const left = this.evaluate(node.left);

		switch (node.operator) {
			case '&&':
				return left ? this.evaluate(node.right) : left;
			case '||':
				// eslint-disable-next-line @typescript-eslint/prefer-nullish-coalescing -- Implementing JS || semantics
				return left ? left : this.evaluate(node.right);
			case '??':
				return left ?? this.evaluate(node.right);
			default:
				throw new UnsupportedNodeError(
					`Logical operator ${String(node.operator)}`,
					node.loc ?? undefined,
					this.sourceCode,
				);
		}
	}

	/**
	 * Visit a conditional expression (ternary).
	 */
	private visitConditionalExpression(node: ESTree.ConditionalExpression): unknown {
		const test = this.evaluate(node.test);
		return test ? this.evaluate(node.consequent) : this.evaluate(node.alternate);
	}

	/**
	 * Visit an assignment expression.
	 * Only allows simple property assignment (obj.prop = value).

View on GitHub (pinned to 5ac6606e81)

Solutions

1. This error should not occur with valid JS — verify the parser and AST source
2. If extending the interpreter: add the new operator to the `visitLogicalExpression` switch
3. Simplify to standard `&&`, `||`, or `??` operators

// Not user-validatable — all standard logical operators are supported.
// If encountered, the AST is malformed or non-standard.

import { UnsupportedNodeError } from '@n8n/workflow-sdk/ast-interpreter/errors';

try {
  interpretSDKCode(sdkCode, sdkFunctions);
} catch (e) {
  if (e instanceof UnsupportedNodeError && e.message.includes('Logical operator')) {
    // log as internal/parser issue — standard JS should never trigger this
  }
  throw e;
}

When it happens

Trigger: Unreachable through valid JavaScript — all standard logical operators (`&&`, `||`, `??`) have cases in the switch at interpreter.ts:667. Could only fire with a non-standard or malformed AST node of type `LogicalExpression` with an unknown operator.

Common situations: Internal development or parser extensions; extremely unlikely in production. Not a user-fixable syntax issue.

Related errors

• Unsupported syntax: 'super keyword is not supported in SDK c
• Failed to decode base64 attachment data
• Unsupported syntax: 'Destructuring in variable declaration'
• '${name}' is a reserved SDK function name and cannot be used
• Expression nesting too deep (possible cycle in method chain)

AI-assisted analysis of n8n-io/n8n@5ac6606e81 (2026-08-12). Data as JSON: /api/errors/b6c52f589a5c53ef. Report an issue: GitHub.