fix: Fix paired item handling of multiple inputs (#16153)

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

@@ -912,106 +912,76 @@ export class WorkflowDataProxy {
 			return outputs;
 		}
 
-		function resolveMultiplePairings(
+		const normalizePairedItem = (
-			pairings: IPairedItemData[],
+			paired: number | IPairedItemData | Array<number | IPairedItemData>,
-			source: ISourceData[],
+		): IPairedItemData[] => {
-			destinationNode: string,
+			const pairedItems = Array.isArray(paired) ? paired : [paired];
-			method: PairedItemMethod,
-			itemIndex: number,
-		): INodeExecutionData {
-			const results = pairings
-				.map((pairing) => {
-					try {
-						const input = pairing.input || 0;
-						if (input >= source.length) {
-							// Could not resolve pairedItem as the defined node input does not exist on source.previousNode.
-							return null;
-						}
-						// eslint-disable-next-line @typescript-eslint/no-use-before-define
-						return getPairedItem(destinationNode, source[input], pairing, method);
-					} catch {
-						return null;
-					}
-				})
-				.filter(Boolean) as INodeExecutionData[];
 
-			if (results.length === 1) return results[0];
+			return pairedItems.map((p) => (typeof p === 'number' ? { item: p } : p));
+		};
 
-			const allSame = results.every((r) => r === results[0]);
-			if (allSame) return results[0];
-
-			throw createPairedItemMultipleItemsFound(destinationNode, itemIndex);
-		}
-
-		/**
-		 * Attempts to find the execution data for a specific paired item
-		 * by traversing the node execution ancestry chain.
-		 */
 		const getPairedItem = (
 			destinationNodeName: string,
 			incomingSourceData: ISourceData | null,
 			initialPairedItem: IPairedItemData,
 			usedMethodName: PairedItemMethod = PAIRED_ITEM_METHOD.$GET_PAIRED_ITEM,
-		): INodeExecutionData | null => {
+			nodeBeforeLast?: string,
+		): INodeExecutionData => {
 			// Step 1: Normalize inputs
 			const [pairedItem, sourceData] = normalizeInputs(initialPairedItem, incomingSourceData);
 
-			let currentPairedItem = pairedItem;
+			if (!sourceData) {
-			let currentSource = sourceData;
+				throw createPairedItemNotFound(destinationNodeName, nodeBeforeLast);
-			let nodeBeforeLast: string | undefined;
-
-			// Step 2: Traverse ancestry to find correct node
-			while (currentSource && currentSource.previousNode !== destinationNodeName) {
-				const taskData = getTaskData(currentSource);
-
-				const outputData = getNodeOutput(taskData, currentSource, nodeBeforeLast);
-				const sourceArray = taskData?.source.filter((s): s is ISourceData => s !== null) ?? [];
-
-				const item = outputData[currentPairedItem.item];
-				if (item?.pairedItem === undefined) {
-					throw createMissingPairedItemError(currentSource.previousNode, usedMethodName);
-				}
-
-				// Multiple pairings? Recurse over all
-				if (Array.isArray(item.pairedItem)) {
-					return resolveMultiplePairings(
-						item.pairedItem,
-						sourceArray,
-						destinationNodeName,
-						usedMethodName,
-						currentPairedItem.item,
-					);
-				}
-
-				// Follow single paired item
-				currentPairedItem =
-					typeof item.pairedItem === 'number' ? { item: item.pairedItem } : item.pairedItem;
-
-				const inputIndex = currentPairedItem.input || 0;
-				if (inputIndex >= sourceArray.length) {
-					if (sourceArray.length === 0) throw createNoConnectionError(destinationNodeName);
-					throw createBranchNotFoundError(
-						currentSource.previousNode,
-						currentPairedItem.item,
-						nodeBeforeLast,
-					);
-				}
-
-				nodeBeforeLast = currentSource.previousNode;
-				currentSource = currentPairedItem.sourceOverwrite || sourceArray[inputIndex];
 			}
 
-			// Step 3: Final node reached — fetch paired item
+			const taskData = getTaskData(sourceData);
-			if (!currentSource) throw createPairedItemNotFound(destinationNodeName, nodeBeforeLast);
+			const outputData = getNodeOutput(taskData, sourceData, nodeBeforeLast);
+			const item = outputData[pairedItem.item];
+			const sourceArray = taskData?.source ?? [];
 
-			const finalTaskData = getTaskData(currentSource);
+			// Done: reached the destination node in the ancestry chain
-			const finalOutputData = getNodeOutput(finalTaskData, currentSource);
+			if (sourceData.previousNode === destinationNodeName) {
+				if (pairedItem.item >= outputData.length) {
+					throw createInvalidPairedItemError({ nodeName: sourceData.previousNode });
+				}
 
-			if (currentPairedItem.item >= finalOutputData.length) {
+				return item;
-				throw createInvalidPairedItemError({ nodeName: currentSource.previousNode });
 			}
 
-			return finalOutputData[currentPairedItem.item];
+			if (!item?.pairedItem) {
+				throw createMissingPairedItemError(sourceData.previousNode, usedMethodName);
+			}
+
+			// Normalize paired item to always be IPairedItemData[]
+			const nextPairedItems = normalizePairedItem(item.pairedItem);
+
+			// Recursively traverse ancestry to find the destination node + paired item
+			const results = nextPairedItems.flatMap((nextPairedItem) => {
+				const inputIndex = nextPairedItem.input ?? 0;
+
+				if (inputIndex >= sourceArray.length) return [];
+
+				const nextSource = nextPairedItem.sourceOverwrite ?? sourceArray[inputIndex];
+				return getPairedItem(
+					destinationNodeName,
+					nextSource,
+					{ ...nextPairedItem, input: inputIndex },
+					usedMethodName,
+					sourceData.previousNode,
+				);
+			});
+
+			if (results.length === 0) {
+				if (sourceArray.length === 0) throw createNoConnectionError(destinationNodeName);
+				throw createBranchNotFoundError(sourceData.previousNode, pairedItem.item, nodeBeforeLast);
+			}
+
+			const [first, ...rest] = results;
+			if (rest.some((r) => r !== first)) {
+				throw createPairedItemMultipleItemsFound(destinationNodeName, pairedItem.item);
+			}
+
+			return first;
 		};
 
 		const handleFromAi = (

packages/workflow/test/fixtures/WorkflowDataProxy/multiple_inputs_run.json

@@ -0,0 +1,114 @@
+{
+	"data": {
+		"startData": {},
+		"resultData": {
+			"runData": {
+				"Manual Trigger": [
+					{
+						"startTime": 1749486952181,
+						"executionIndex": 0,
+						"source": [],
+						"hints": [],
+						"executionTime": 2,
+						"executionStatus": "success",
+						"data": { "main": [[{ "json": {}, "pairedItem": { "item": 0 } }]] }
+					}
+				],
+				"Set main variable": [
+					{
+						"startTime": 1749486952183,
+						"executionIndex": 1,
+						"source": [{ "previousNode": "Manual Trigger" }],
+						"hints": [],
+						"executionTime": 2,
+						"executionStatus": "success",
+						"data": { "main": [[{ "json": { "main_variable": 2 }, "pairedItem": { "item": 0 } }]] }
+					}
+				],
+				"Set variable_1": [
+					{
+						"startTime": 1749486952185,
+						"executionIndex": 2,
+						"source": [{ "previousNode": "Set main variable" }],
+						"hints": [],
+						"executionTime": 0,
+						"executionStatus": "success",
+						"data": {
+							"main": [[{ "json": { "variable_1": "1234" }, "pairedItem": { "item": 0 } }]]
+						}
+					}
+				],
+				"Set variable_2": [
+					{
+						"startTime": 1749486952186,
+						"executionIndex": 3,
+						"source": [{ "previousNode": "Set main variable" }],
+						"hints": [],
+						"executionTime": 0,
+						"executionStatus": "success",
+						"data": {
+							"main": [[{ "json": { "variable_2": "2345" }, "pairedItem": { "item": 0 } }]]
+						}
+					}
+				],
+				"Set variable_3": [
+					{
+						"startTime": 1749486952187,
+						"executionIndex": 4,
+						"source": [{ "previousNode": "Set main variable" }],
+						"hints": [],
+						"executionTime": 0,
+						"executionStatus": "success",
+						"data": {
+							"main": [[{ "json": { "variable_3": "3456" }, "pairedItem": { "item": 0 } }]]
+						}
+					}
+				],
+				"Merge": [
+					{
+						"startTime": 1749486952197,
+						"executionIndex": 5,
+						"source": [null, null, { "previousNode": "Set variable_3" }],
+						"hints": [],
+						"executionTime": 12,
+						"executionStatus": "success",
+						"data": {
+							"main": [
+								[{ "json": { "variable_3": "3456" }, "pairedItem": { "item": 0, "input": 2 } }]
+							]
+						}
+					}
+				],
+				"Output": [
+					{
+						"startTime": 1749486952210,
+						"executionIndex": 6,
+						"source": [{ "previousNode": "Merge" }],
+						"hints": [],
+						"executionTime": 4,
+						"executionStatus": "success",
+						"data": {
+							"main": [
+								[
+									{
+										"json": { "final_variable_2": "3456", "main": "2" },
+										"pairedItem": { "item": 0 }
+									}
+								]
+							]
+						}
+					}
+				]
+			},
+			"pinData": {},
+			"lastNodeExecuted": "Output"
+		},
+		"executionData": {
+			"contextData": {},
+			"nodeExecutionStack": [],
+			"metadata": {},
+			"waitingExecution": {},
+			"waitingExecutionSource": {}
+		}
+	}
+}

packages/workflow/test/fixtures/WorkflowDataProxy/multiple_inputs_workflow.json

@@ -0,0 +1,203 @@
+{
+	"name": "Paired item",
+	"nodes": [
+		{
+			"parameters": {
+				"numberInputs": 3
+			},
+			"type": "n8n-nodes-base.merge",
+			"typeVersion": 3.1,
+			"position": [560, 300],
+			"id": "2b68168b-1494-4c4b-b416-b4fb6bb0afd8",
+			"name": "Merge",
+			"alwaysOutputData": true
+		},
+		{
+			"parameters": {
+				"assignments": {
+					"assignments": [
+						{
+							"id": "63830a30-a4cc-4a66-9d01-8f0a058d4d43",
+							"name": "variable_1",
+							"value": "1234",
+							"type": "string"
+						}
+					]
+				},
+				"options": {}
+			},
+			"type": "n8n-nodes-base.set",
+			"typeVersion": 3.4,
+			"position": [200, 100],
+			"id": "a1d151cc-8f44-43c6-962f-baecb879d33c",
+			"name": "Set variable_1"
+		},
+		{
+			"parameters": {
+				"assignments": {
+					"assignments": [
+						{
+							"id": "63830a30-a4cc-4a66-9d01-8f0a058d4d43",
+							"name": "variable_2",
+							"value": "2345",
+							"type": "string"
+						}
+					]
+				},
+				"options": {}
+			},
+			"type": "n8n-nodes-base.set",
+			"typeVersion": 3.4,
+			"position": [200, 300],
+			"id": "404ff876-b524-4873-8dc0-36664639907a",
+			"name": "Set variable_2"
+		},
+		{
+			"parameters": {
+				"assignments": {
+					"assignments": [
+						{
+							"id": "63830a30-a4cc-4a66-9d01-8f0a058d4d43",
+							"name": "variable_3",
+							"value": "3456",
+							"type": "string"
+						}
+					]
+				},
+				"options": {}
+			},
+			"type": "n8n-nodes-base.set",
+			"typeVersion": 3.4,
+			"position": [200, 500],
+			"id": "d403e979-7651-4acf-8e08-1d342b7abe7f",
+			"name": "Set variable_3"
+		},
+		{
+			"parameters": {
+				"assignments": {
+					"assignments": [
+						{
+							"id": "89862e7d-0c44-4d6a-897e-a249c06f6346",
+							"name": "final_variable_2",
+							"value": "={{ $('Set variable_3').item.json.variable_3 }}",
+							"type": "string"
+						},
+						{
+							"id": "060e841c-c236-41ae-9396-e23566825f47",
+							"name": "main",
+							"value": "={{ $('Set main variable').item.json.main_variable }}",
+							"type": "string"
+						}
+					]
+				},
+				"options": {}
+			},
+			"type": "n8n-nodes-base.set",
+			"typeVersion": 3.4,
+			"position": [840, 300],
+			"id": "16514f79-e309-465c-b571-7d81e268d7f0",
+			"name": "Output"
+		},
+		{
+			"parameters": {},
+			"type": "n8n-nodes-base.manualTrigger",
+			"typeVersion": 1,
+			"position": [-240, 300],
+			"id": "3a8a9543-567c-443c-8742-fa0a8d9fb2e7",
+			"name": "Manual Trigger"
+		},
+		{
+			"parameters": {
+				"assignments": {
+					"assignments": [
+						{
+							"id": "6bb9d060-adee-429f-884d-5009ab1a1811",
+							"name": "main_variable",
+							"value": 2,
+							"type": "number"
+						}
+					]
+				},
+				"options": {}
+			},
+			"type": "n8n-nodes-base.set",
+			"typeVersion": 3.4,
+			"position": [-20, 300],
+			"id": "b6ec9c0f-de04-45d3-a402-3969251a6914",
+			"name": "Set main variable"
+		}
+	],
+	"pinData": {},
+	"connections": {
+		"Merge": {
+			"main": [
+				[
+					{
+						"node": "Output",
+						"type": "main",
+						"index": 0
+					}
+				]
+			]
+		},
+		"Set variable_1": {
+			"main": [[]]
+		},
+		"Set variable_2": {
+			"main": [[]]
+		},
+		"Set variable_3": {
+			"main": [
+				[
+					{
+						"node": "Merge",
+						"type": "main",
+						"index": 2
+					}
+				]
+			]
+		},
+		"Manual Trigger": {
+			"main": [
+				[
+					{
+						"node": "Set main variable",
+						"type": "main",
+						"index": 0
+					}
+				]
+			]
+		},
+		"Set main variable": {
+			"main": [
+				[
+					{
+						"node": "Set variable_2",
+						"type": "main",
+						"index": 0
+					},
+					{
+						"node": "Set variable_1",
+						"type": "main",
+						"index": 0
+					},
+					{
+						"node": "Set variable_3",
+						"type": "main",
+						"index": 0
+					}
+				]
+			]
+		}
+	},
+	"active": false,
+	"settings": {
+		"executionOrder": "v1"
+	},
+	"versionId": "5678abcc-b267-4b5b-ba1b-5f7bb1b085ec",
+	"meta": {
+		"instanceId": "27cc9b56542ad45b38725555722c50a1c3fee1670bbb67980558314ee08517c4"
+	},
+	"id": "TakJu1jBtMGTFXEA",
+	"tags": []
+}

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

@@ -835,4 +835,14 @@ describe('WorkflowDataProxy', () => {
 			expect(tools[0].aiDefinedFields).toEqual(['Start']);
 		});
 	});
+
+	describe('multiple inputs', () => {
+		const fixture = loadFixture('multiple_inputs');
+
+		it('should correctly resolve expressions with multiple inputs (using paired item)', () => {
+			const proxy = getProxyFromFixture(fixture.workflow, fixture.run, 'Output');
+			expect(proxy.$('Set variable_3').item.json.variable_3).toEqual('3456');
+			expect(proxy.$('Set main variable').item.json.main_variable).toEqual(2);
+		});
+	});
 });