fix: Fix resolving of expressions of deeply nested sub-nodes (#8612)

packages/workflow/src/Workflow.ts

@@ -43,8 +43,9 @@ import type {
 	NodeParameterValueType,
 	ConnectionTypes,
 	CloseFunction,
+	INodeOutputConfiguration,
 } from './Interfaces';
-import { Node } from './Interfaces';
+import { Node, NodeConnectionType } from './Interfaces';
 import type { IDeferredPromise } from './DeferredPromise';
 
 import * as NodeHelpers from './NodeHelpers';
@@ -845,6 +846,47 @@ export class Workflow {
 		return returnConns;
 	}
 
+	getParentMainInputNode(node: INode): INode {
+		if (node) {
+			const nodeType = this.nodeTypes.getByNameAndVersion(node.type, node.typeVersion);
+			const outputs = NodeHelpers.getNodeOutputs(this, node, nodeType.description);
+
+			if (
+				!!outputs.find(
+					(output) =>
+						((output as INodeOutputConfiguration)?.type ?? output) !== NodeConnectionType.Main,
+				)
+			) {
+				// Get the first node which is connected to a non-main output
+				const nonMainNodesConnected = outputs?.reduce((acc, outputName) => {
+					const parentNodes = this.getChildNodes(
+						node.name,
+						(outputName as INodeOutputConfiguration)?.type ?? outputName,
+					);
+					if (parentNodes.length > 0) {
+						acc.push(...parentNodes);
+					}
+					return acc;
+				}, [] as string[]);
+
+				if (nonMainNodesConnected.length) {
+					const returnNode = this.getNode(nonMainNodesConnected[0]);
+					if (returnNode === null) {
+						// This should theoretically never happen as the node is connected
+						// but who knows and it makes TS happy
+						throw new ApplicationError(`Node "${nonMainNodesConnected[0]}" not found`);
+					}
+
+					// The chain of non-main nodes is potentially not finished yet so
+					// keep on going
+					return this.getParentMainInputNode(returnNode);
+				}
+			}
+		}
+
+		return node;
+	}
+
 	/**
 	 * Returns via which output of the parent-node and index the current node
 	 * they are connected

packages/workflow/src/WorkflowDataProxy.ts

@@ -993,7 +993,13 @@ export class WorkflowDataProxy {
 
 									// Before resolving the pairedItem make sure that the requested node comes in the
 									// graph before the current one
-									const parentNodes = that.workflow.getParentNodes(that.contextNodeName);
+									const activeNode = that.workflow.getNode(that.activeNodeName);
+									let contextNode = that.contextNodeName;
+									if (activeNode) {
+										const parentMainInputNode = that.workflow.getParentMainInputNode(activeNode);
+										contextNode = parentMainInputNode.name ?? contextNode;
+									}
+									const parentNodes = that.workflow.getParentNodes(contextNode);
 									if (!parentNodes.includes(nodeName)) {
 										throw createExpressionError('Invalid expression', {
 											messageTemplate: 'Invalid expression under ‘%%PARAMETER%%’',