fix: coerce node parameters to string before normalising

An n8n expression such as {{ $json.vatId }} resolves to undefined on an
item without that field, so vatId and countryCode reached normalisation as
undefined and crashed with "Cannot read properties of undefined (reading
'toUpperCase')" wrapped in a NodeApiError. Coerce both, guard the empty
country code the same way the VAT number already was, and let input errors
surface as NodeOperationError instead of being reported as API failures.

Release 1.0.1.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Author: rogulia

nodes/Vatnode/Vatnode.node.ts

@@ -19,6 +19,14 @@ function normalizeVatId(vatId: string): string {
 	return vatId.toUpperCase().replace(/[^A-Z0-9]/g, '');
 }
 
+/**
+ * An expression such as {{ $json.vatId }} resolves to undefined on an item that
+ * lacks the field, so a parameter typed as string is not guaranteed to be one.
+ */
+function toStringParam(value: unknown): string {
+	return value === undefined || value === null ? '' : String(value);
+}
+
 export class Vatnode implements INodeType {
 	description: INodeTypeDescription = {
 		displayName: 'vatnode',
@@ -163,9 +171,9 @@ export class Vatnode implements INodeType {
 				let result: unknown;
 
 				if (resource === 'vat' && operation === 'checkFormat') {
-					result = checkFormat(this.getNodeParameter('vatId', i) as string);
+					result = checkFormat(toStringParam(this.getNodeParameter('vatId', i)));
 				} else if (resource === 'vat' && operation === 'validate') {
-					const vatId = normalizeVatId(this.getNodeParameter('vatId', i) as string);
+					const vatId = normalizeVatId(toStringParam(this.getNodeParameter('vatId', i)));
 					if (vatId === '') {
 						throw new NodeOperationError(this.getNode(), 'The VAT number is empty', {
 							itemIndex: i,
@@ -178,7 +186,12 @@ export class Vatnode implements INodeType {
 					};
 					result = await this.helpers.httpRequestWithAuthentication.call(this, 'vatnodeApi', options);
 				} else if (resource === 'rate' && operation === 'get') {
-					const input = (this.getNodeParameter('countryCode', i) as string).trim().toUpperCase();
+					const input = toStringParam(this.getNodeParameter('countryCode', i)).trim().toUpperCase();
+					if (input === '') {
+						throw new NodeOperationError(this.getNode(), 'The country code is empty', {
+							itemIndex: i,
+						});
+					}
 					// VIES writes Greece as EL, the rate endpoint keys it as GR.
 					const countryCode = input === 'EL' ? 'GR' : input;
 					result = await this.helpers.httpRequest({
@@ -217,6 +230,10 @@ export class Vatnode implements INodeType {
 					});
 					continue;
 				}
+				// Input problems are ours, not the API's — keep them out of NodeApiError.
+				if (error instanceof NodeOperationError) {
+					throw new NodeOperationError(this.getNode(), error.message, { itemIndex: i });
+				}
 				throw new NodeApiError(this.getNode(), error as JsonObject, { itemIndex: i });
 			}
 		}

package-lock.json

@@ -1,6 +1,6 @@
 {
   "name": "n8n-nodes-vatnode",
-  "version": "1.0.0",
+  "version": "1.0.1",
   "description": "Validate EU VAT numbers against VIES and look up EU VAT rates in n8n, powered by vatnode.",
   "keywords": [
     "n8n-community-node-package",