fix(Remove Duplicates Node): Tolerate null fields (#9642)

packages/nodes-base/nodes/Transform/RemoveDuplicates/utils.ts

@@ -3,7 +3,12 @@ import isEqual from 'lodash/isEqual';
 import isObject from 'lodash/isObject';
 import merge from 'lodash/merge';
 import reduce from 'lodash/reduce';
-import type { IDataObject, INode, INodeExecutionData } from 'n8n-workflow';
+import {
+	NodeOperationError,
+	type IDataObject,
+	type INode,
+	type INodeExecutionData,
+} from 'n8n-workflow';
 
 export const compareItems = (
 	obj: INodeExecutionData,
@@ -34,3 +39,42 @@ export const flattenKeys = (obj: IDataObject, path: string[] = []): IDataObject
 		? { [path.join('.')]: obj }
 		: reduce(obj, (cum, next, key) => merge(cum, flattenKeys(next as IDataObject, [...path, key])), {}); //prettier-ignore
 };
+
+export const validateInputData = (
+	node: INode,
+	items: INodeExecutionData[],
+	keysToCompare: string[],
+	disableDotNotation: boolean,
+) => {
+	for (const key of keysToCompare) {
+		let type: any = undefined;
+		for (const [i, item] of items.entries()) {
+			if (key === '') {
+				throw new NodeOperationError(node, 'Name of field to compare is blank');
+			}
+			const value = !disableDotNotation ? get(item.json, key) : item.json[key];
+			if (value === null && node.typeVersion > 1) continue;
+
+			if (value === undefined && disableDotNotation && key.includes('.')) {
+				throw new NodeOperationError(node, `'${key}' field is missing from some input items`, {
+					description:
+						"If you're trying to use a nested field, make sure you turn off 'disable dot notation' in the node options",
+				});
+			} else if (value === undefined) {
+				throw new NodeOperationError(node, `'${key}' field is missing from some input items`);
+			}
+			if (type !== undefined && value !== undefined && type !== typeof value) {
+				const description =
+					'The type of this field varies between items' +
+					(node.typeVersion > 1
+						? `, in item [${i - 1}] it's a ${type} and in item [${i}] it's a ${typeof value} `
+						: '');
+				throw new NodeOperationError(node, `'${key}' isn't always the same type`, {
+					description,
+				});
+			} else {
+				type = typeof value;
+			}
+		}
+	}
+};