fix(core): Replace misleading "No path back to node" error with helpful execution message (#17759)

Author: cstuncsik

packages/workflow/src/workflow-data-proxy.ts

@@ -1080,7 +1080,13 @@ export class WorkflowDataProxy {
 						!that?.runExecutionData?.resultData?.runData.hasOwnProperty(nodeName) &&
 						!getPinDataIfManualExecution(that.workflow, nodeName, that.mode)
 					) {
-						throw createNodeReferenceError(nodeName);
+						// Always show helpful "Execute node for preview" message
+						throw new ExpressionError(EXPRESSION_ERROR_MESSAGES.NO_EXECUTION_DATA, {
+							messageTemplate: `Execute node "${nodeName}" for preview`,
+							nodeCause: nodeName,
+							runIndex: that.runIndex,
+							itemIndex: that.itemIndex,
+						});
 					}
 				};
 
@@ -1098,7 +1104,10 @@ export class WorkflowDataProxy {
 						contextNode = parentMainInputNode?.name ?? contextNode;
 					}
 
-					if (!that.workflow.hasPath(nodeName, contextNode)) {
+					// For .first(), .last(), .all() methods, use unidirectional path checking
+					// (forward only) to maintain traditional paired item behavior
+					const hasForwardPath = that.workflow.getChildNodes(nodeName).includes(contextNode);
+					if (!hasForwardPath) {
 						throw createNodeReferenceError(nodeName);
 					}
 				};

packages/workflow/src/workflow.ts

@@ -676,13 +676,24 @@ export class Workflow {
 		return returnConns;
 	}
 
-	getParentMainInputNode(node: INode | null | undefined): INode | null | undefined {
+	getParentMainInputNode(
+		node: INode | null | undefined,
+		visitedNodes: Set<string> = new Set(),
+	): INode | null | undefined {
 		if (!node) return node;
 
+		// Prevent infinite recursion by tracking visited nodes
+		if (visitedNodes.has(node.name)) {
+			return node;
+		}
+		visitedNodes.add(node.name);
+
 		const nodeConnections = this.connectionsBySourceNode[node.name];
-		if (!nodeConnections) return node;
+		if (!nodeConnections) {
+			return node;
+		}
 
-		// Get non-main connection types
+		// Get non-main connection types that this node connects TO (outgoing connections)
 		const nonMainConnectionTypes = Object.keys(nodeConnections).filter(
 			(type) => type !== NodeConnectionTypes.Main,
 		);
@@ -696,7 +707,7 @@ export class Workflow {
 						if (!returnNode) {
 							throw new ApplicationError(`Node "${connection.node}" not found`);
 						}
-						return this.getParentMainInputNode(returnNode);
+						return this.getParentMainInputNode(returnNode, visitedNodes);
 					}
 				}
 			}