feat(core)!: Change data processing for multi-input-nodes (#4238)

Co-authored-by: कारतोफ्फेलस्क्रिप्ट™ <aditya@netroy.in>

packages/core/src/WorkflowExecute.ts

@@ -143,6 +143,26 @@ export class WorkflowExecute {
 		return this.processRunExecutionData(workflow);
 	}
 
+	forceInputNodeExecution(workflow: Workflow, node: INode): boolean {
+		const nodeType = workflow.nodeTypes.getByNameAndVersion(node.type, node.typeVersion);
+
+		// Check if the incoming nodes should be forced to execute
+		let forceInputNodeExecution = nodeType.description.forceInputNodeExecution;
+		if (forceInputNodeExecution !== undefined) {
+			if (typeof forceInputNodeExecution === 'string') {
+				forceInputNodeExecution = !!workflow.expression.getSimpleParameterValue(
+					node,
+					forceInputNodeExecution,
+					this.mode,
+					this.additionalData.timezone,
+					{ $version: node.typeVersion },
+				);
+			}
+			return forceInputNodeExecution;
+		}
+		return false;
+	}
+
 	/**
 	 * Executes the given workflow but only
 	 *
@@ -329,6 +349,27 @@ export class WorkflowExecute {
 		return true;
 	}
 
+	prepareWaitingToExecution(nodeName: string, numberOfConnections: number, runIndex: number) {
+		if (!this.runExecutionData.executionData!.waitingExecutionSource) {
+			this.runExecutionData.executionData!.waitingExecutionSource = {};
+		}
+
+		this.runExecutionData.executionData!.waitingExecution[nodeName][runIndex] = {
+			main: [],
+		};
+		this.runExecutionData.executionData!.waitingExecutionSource[nodeName][runIndex] = {
+			main: [],
+		};
+
+		for (let i = 0; i < numberOfConnections; i++) {
+			this.runExecutionData.executionData!.waitingExecution[nodeName][runIndex].main.push(null);
+
+			this.runExecutionData.executionData!.waitingExecutionSource[nodeName][runIndex].main.push(
+				null,
+			);
+		}
+	}
+
 	addNodeToBeExecuted(
 		workflow: Workflow,
 		connectionData: IConnection,
@@ -338,6 +379,7 @@ export class WorkflowExecute {
 		runIndex: number,
 	): void {
 		let stillDataMissing = false;
+		let waitingNodeIndex: number | undefined;
 
 		// Check if node has multiple inputs as then we have to wait for all input data
 		// to be present before we can add it to the node-execution-stack
@@ -358,47 +400,64 @@ export class WorkflowExecute {
 				this.runExecutionData.executionData!.waitingExecutionSource[connectionData.node] = {};
 				nodeWasWaiting = false;
 			}
-			if (
-				this.runExecutionData.executionData!.waitingExecution[connectionData.node][runIndex] ===
-				undefined
-			) {
-				// Node does not have data for runIndex yet so create also empty one and init it
-				this.runExecutionData.executionData!.waitingExecution[connectionData.node][runIndex] = {
-					main: [],
-				};
-				this.runExecutionData.executionData!.waitingExecutionSource[connectionData.node][runIndex] =
-					{
-						main: [],
-					};
-				for (
-					let i = 0;
-					i < workflow.connectionsByDestinationNode[connectionData.node].main.length;
-					i++
-				) {
-					this.runExecutionData.executionData!.waitingExecution[connectionData.node][
-						runIndex
-					].main.push(null);
 
-					this.runExecutionData.executionData!.waitingExecutionSource[connectionData.node][
-						runIndex
-					].main.push(null);
+			// Figure out if the node is already waiting with partial data to which to add the
+			// data to or if a new entry has to get created
+			let createNewWaitingEntry = true;
+
+			if (
+				Object.keys(this.runExecutionData.executionData!.waitingExecution[connectionData.node])
+					.length > 0
+			) {
+				// Check if there is already data for the input on all of the waiting nodes
+				for (const index of Object.keys(
+					this.runExecutionData.executionData!.waitingExecution[connectionData.node],
+				)) {
+					if (
+						!this.runExecutionData.executionData!.waitingExecution[connectionData.node][
+							parseInt(index)
+						].main[connectionData.index]
+					) {
+						// Data for the input is missing so we can add it to the existing entry
+						createNewWaitingEntry = false;
+						waitingNodeIndex = parseInt(index);
+						break;
+					}
 				}
 			}
 
+			if (waitingNodeIndex === undefined) {
+				waitingNodeIndex = Object.values(
+					this.runExecutionData.executionData!.waitingExecution[connectionData.node],
+				).length;
+			}
+
+			if (createNewWaitingEntry) {
+				// There is currently no node waiting that does not already have data for
+				// the given input, so create a new entry
+
+				this.prepareWaitingToExecution(
+					connectionData.node,
+					workflow.connectionsByDestinationNode[connectionData.node].main.length,
+					waitingNodeIndex,
+				);
+			}
+
 			// Add the new data
 			if (nodeSuccessData === null) {
-				this.runExecutionData.executionData!.waitingExecution[connectionData.node][runIndex].main[
-					connectionData.index
-				] = null;
+				this.runExecutionData.executionData!.waitingExecution[connectionData.node][
+					waitingNodeIndex
+				].main[connectionData.index] = null;
 				this.runExecutionData.executionData!.waitingExecutionSource[connectionData.node][
-					runIndex
+					waitingNodeIndex
 				].main[connectionData.index] = null;
 			} else {
-				this.runExecutionData.executionData!.waitingExecution[connectionData.node][runIndex].main[
-					connectionData.index
-				] = nodeSuccessData[outputIndex];
+				this.runExecutionData.executionData!.waitingExecution[connectionData.node][
+					waitingNodeIndex
+				].main[connectionData.index] = nodeSuccessData[outputIndex];
+
 				this.runExecutionData.executionData!.waitingExecutionSource[connectionData.node][
-					runIndex
+					waitingNodeIndex
 				].main[connectionData.index] = {
 					previousNode: parentNodeName,
 					previousNodeOutput: outputIndex || undefined,
@@ -412,14 +471,14 @@ export class WorkflowExecute {
 			for (
 				let i = 0;
 				i <
-				this.runExecutionData.executionData!.waitingExecution[connectionData.node][runIndex].main
-					.length;
+				this.runExecutionData.executionData!.waitingExecution[connectionData.node][waitingNodeIndex]
+					.main.length;
 				i++
 			) {
 				thisExecutionData =
-					this.runExecutionData.executionData!.waitingExecution[connectionData.node][runIndex].main[
-						i
-					];
+					this.runExecutionData.executionData!.waitingExecution[connectionData.node][
+						waitingNodeIndex
+					].main[i];
 				if (thisExecutionData === null) {
 					allDataFound = false;
 					break;
@@ -433,11 +492,11 @@ export class WorkflowExecute {
 				const executionStackItem = {
 					node: workflow.nodes[connectionData.node],
 					data: this.runExecutionData.executionData!.waitingExecution[connectionData.node][
-						runIndex
+						waitingNodeIndex
 					],
 					source:
 						this.runExecutionData.executionData!.waitingExecutionSource[connectionData.node][
-							runIndex
+							waitingNodeIndex
 						],
 				} as IExecuteData;
 
@@ -447,16 +506,18 @@ export class WorkflowExecute {
 				) {
 					executionStackItem.source =
 						this.runExecutionData.executionData!.waitingExecutionSource[connectionData.node][
-							runIndex
+							waitingNodeIndex
 						];
 				}
 
 				this.runExecutionData.executionData!.nodeExecutionStack.unshift(executionStackItem);
 
 				// Remove the data from waiting
-				delete this.runExecutionData.executionData!.waitingExecution[connectionData.node][runIndex];
+				delete this.runExecutionData.executionData!.waitingExecution[connectionData.node][
+					waitingNodeIndex
+				];
 				delete this.runExecutionData.executionData!.waitingExecutionSource[connectionData.node][
-					runIndex
+					waitingNodeIndex
 				];
 
 				if (
@@ -492,6 +553,10 @@ export class WorkflowExecute {
 				// checked. So we have to go through all the inputs and check if they
 				// are already on the list to be processed.
 				// If that is not the case add it.
+
+				const node = workflow.getNode(connectionData.node);
+				const forceInputNodeExecution = this.forceInputNodeExecution(workflow, node!);
+
 				for (
 					let inputIndex = 0;
 					inputIndex < workflow.connectionsByDestinationNode[connectionData.node].main.length;
@@ -540,6 +605,12 @@ export class WorkflowExecute {
 							continue;
 						}
 
+						if (!forceInputNodeExecution) {
+							// Do not automatically follow all incoming nodes and force them
+							// to execute
+							continue;
+						}
+
 						// Check if any of the parent nodes does not have any inputs. That
 						// would mean that it has to get added to the list of nodes to process.
 						const parentNodes = workflow.getParentNodes(inputData.node, 'main', -1);
@@ -650,14 +721,26 @@ export class WorkflowExecute {
 		}
 
 		if (stillDataMissing) {
+			waitingNodeIndex = waitingNodeIndex!;
+
 			// Additional data is needed to run node so add it to waiting
-			if (
-				!this.runExecutionData.executionData!.waitingExecution.hasOwnProperty(connectionData.node)
-			) {
-				this.runExecutionData.executionData!.waitingExecution[connectionData.node] = {};
-			}
-			this.runExecutionData.executionData!.waitingExecution[connectionData.node][runIndex] = {
-				main: connectionDataArray,
+			this.prepareWaitingToExecution(
+				connectionData.node,
+				workflow.connectionsByDestinationNode[connectionData.node].main.length,
+				waitingNodeIndex,
+			);
+
+			this.runExecutionData.executionData!.waitingExecution[connectionData.node][waitingNodeIndex] =
+				{
+					main: connectionDataArray,
+				};
+
+			this.runExecutionData.executionData!.waitingExecutionSource![connectionData.node][
+				waitingNodeIndex
+			].main[connectionData.index] = {
+				previousNode: parentNodeName,
+				previousNodeOutput: outputIndex || undefined,
+				previousNodeRun: runIndex || undefined,
 			};
 		} else {
 			// All data is there so add it directly to stack
@@ -854,6 +937,8 @@ export class WorkflowExecute {
 						continue;
 					}
 
+					const node = workflow.getNode(executionNode.name);
+
 					// Check if all the data which is needed to run the node is available
 					if (workflow.connectionsByDestinationNode.hasOwnProperty(executionNode.name)) {
 						// Check if the node has incoming connections
@@ -886,17 +971,20 @@ export class WorkflowExecute {
 									continue executionLoop;
 								}
 
-								// Check if it has the data for all the inputs
-								// The most nodes just have one but merge node for example has two and data
-								// of both inputs has to be available to be able to process the node.
-								if (
-									executionData.data.main.length < connectionIndex ||
-									executionData.data.main[connectionIndex] === null
-								) {
-									// Does not have the data of the connections so add back to stack
-									this.runExecutionData.executionData!.nodeExecutionStack.push(executionData);
-									lastExecutionTry = currentExecutionTry;
-									continue executionLoop;
+								if (this.forceInputNodeExecution(workflow, node!)) {
+									// Check if it has the data for all the inputs
+									// The most nodes just have one but merge node for example has two and data
+									// of both inputs has to be available to be able to process the node.
+									if (
+										executionData.data.main.length < connectionIndex ||
+										executionData.data.main[connectionIndex] === null
+									) {
+										// Does not have the data of the connections so add back to stack
+										this.runExecutionData.executionData!.nodeExecutionStack.push(executionData);
+										lastExecutionTry = currentExecutionTry;
+
+										continue executionLoop;
+									}
 								}
 							}
 						}
@@ -1207,9 +1295,16 @@ export class WorkflowExecute {
 										);
 									}
 
+									const connectionDestinationNode = workflow.getNode(connectionData.node);
+									const forceInputNodeExecution = this.forceInputNodeExecution(
+										workflow,
+										connectionDestinationNode!,
+									);
+
 									if (
 										nodeSuccessData![outputIndex] &&
-										(nodeSuccessData![outputIndex].length !== 0 || connectionData.index > 0)
+										(nodeSuccessData![outputIndex].length !== 0 ||
+											(connectionData.index > 0 && forceInputNodeExecution))
 									) {
 										// Add the node only if it did execute or if connected to second "optional" input
 										const nodeToAdd = workflow.getNode(connectionData.node);
@@ -1260,6 +1355,163 @@ export class WorkflowExecute {
 						taskData,
 						this.runExecutionData,
 					]);
+
+					let waitingNodes: string[] = Object.keys(
+						this.runExecutionData.executionData!.waitingExecution,
+					);
+
+					if (
+						this.runExecutionData.executionData!.nodeExecutionStack.length === 0 &&
+						waitingNodes.length
+					) {
+						// There are no more nodes in the execution stack. Check if there are
+						// waiting nodes that do not require data on all inputs and execute them,
+						// one by one.
+
+						// TODO: Should this also care about workflow position (top-left first?)
+						for (let i = 0; i < waitingNodes.length; i++) {
+							const nodeName = waitingNodes[i];
+
+							const checkNode = workflow.getNode(nodeName);
+							if (!checkNode) {
+								continue;
+							}
+							const nodeType = workflow.nodeTypes.getByNameAndVersion(
+								checkNode.type,
+								checkNode.typeVersion,
+							);
+
+							// Check if the node is only allowed execute if all inputs received data
+							let requiredInputs = nodeType.description.requiredInputs;
+							if (requiredInputs !== undefined) {
+								if (typeof requiredInputs === 'string') {
+									requiredInputs = workflow.expression.getSimpleParameterValue(
+										checkNode,
+										requiredInputs,
+										this.mode,
+										this.additionalData.timezone,
+										{ $version: checkNode.typeVersion },
+										undefined,
+										[],
+									) as number[];
+								}
+
+								if (
+									(requiredInputs !== undefined &&
+										Array.isArray(requiredInputs) &&
+										requiredInputs.length === nodeType.description.inputs.length) ||
+									requiredInputs === nodeType.description.inputs.length
+								) {
+									// All inputs are required, but not all have data so do not continue
+									continue;
+								}
+							}
+
+							const parentNodes = workflow.getParentNodes(nodeName);
+
+							// Check if input nodes (of same run) got already executed
+							// eslint-disable-next-line @typescript-eslint/no-loop-func
+							const parentIsWaiting = parentNodes.some((value) => waitingNodes.includes(value));
+							if (parentIsWaiting) {
+								// Execute node later as one of its dependencies is still outstanding
+								continue;
+							}
+
+							const runIndexes = Object.keys(
+								this.runExecutionData.executionData!.waitingExecution[nodeName],
+							).sort();
+
+							// The run-index of the earliest outstanding one
+							const firstRunIndex = parseInt(runIndexes[0]);
+
+							// Find all the inputs which received any kind of data, even if it was an empty
+							// array as this shows that the parent nodes executed but they did not have any
+							// data to pass on.
+							const inputsWithData = this.runExecutionData
+								.executionData!.waitingExecution[nodeName][firstRunIndex].main.map((data, index) =>
+									data === null ? null : index,
+								)
+								.filter((data) => data !== null);
+
+							if (requiredInputs !== undefined) {
+								// Certain inputs are required that the node can execute
+
+								if (Array.isArray(requiredInputs)) {
+									// Specific inputs are required (array of input indexes)
+									let inputDataMissing = false;
+									for (const requiredInput of requiredInputs) {
+										if (!inputsWithData.includes(requiredInput)) {
+											inputDataMissing = true;
+											break;
+										}
+									}
+									if (inputDataMissing) {
+										continue;
+									}
+								} else {
+									// A certain amout of inputs are required (amount of inputs)
+									if (inputsWithData.length < requiredInputs) {
+										continue;
+									}
+								}
+							}
+
+							const taskDataMain = this.runExecutionData.executionData!.waitingExecution[nodeName][
+								firstRunIndex
+							].main.map((data) => {
+								// For the inputs for which never any data got received set it to an empty array
+								return data === null ? [] : data;
+							});
+
+							if (taskDataMain.filter((data) => data.length).length !== 0) {
+								// Add the node to be executed
+
+								// Make sure that each input at least receives an empty array
+								if (taskDataMain.length < nodeType.description.inputs.length) {
+									for (; taskDataMain.length < nodeType.description.inputs.length; ) {
+										taskDataMain.push([]);
+									}
+								}
+
+								this.runExecutionData.executionData!.nodeExecutionStack.push({
+									node: workflow.nodes[nodeName],
+									data: {
+										main: taskDataMain,
+									},
+									source:
+										this.runExecutionData.executionData!.waitingExecutionSource![nodeName][
+											firstRunIndex
+										],
+								});
+							}
+
+							// Remove the node from waiting
+							delete this.runExecutionData.executionData!.waitingExecution[nodeName][firstRunIndex];
+							delete this.runExecutionData.executionData!.waitingExecutionSource![nodeName][
+								firstRunIndex
+							];
+
+							if (
+								Object.keys(this.runExecutionData.executionData!.waitingExecution[nodeName])
+									.length === 0
+							) {
+								// No more data left for the node so also delete that one
+								delete this.runExecutionData.executionData!.waitingExecution[nodeName];
+								delete this.runExecutionData.executionData!.waitingExecutionSource![nodeName];
+							}
+
+							if (taskDataMain.filter((data) => data.length).length !== 0) {
+								// Node to execute got found and added to stop
+								break;
+							} else {
+								// Node to add did not get found, rather an empty one removed so continue with search
+								waitingNodes = Object.keys(this.runExecutionData.executionData!.waitingExecution);
+								// Set counter to start again from the beginning. Set it to -1 as it auto increments
+								// after run. So only like that will we end up again ot 0.
+								i = -1;
+							}
+						}
+					}
 				}
 
 				return;

packages/core/test/WorkflowExecute.test.ts

@@ -57,7 +57,6 @@ describe('WorkflowExecute', () => {
 						return nodeData.data.main[0]!.map((entry) => entry.json);
 					});
 
-					// expect(resultData).toEqual(testData.output.nodeData[nodeName]);
 					expect(resultData).toEqual(testData.output.nodeData[nodeName]);
 				}
 

packages/nodes-base/nodes/CompareDatasets/CompareDatasets.node.ts

@@ -18,12 +18,14 @@ export class CompareDatasets implements INodeType {
 		name: 'compareDatasets',
 		icon: 'file:compare.svg',
 		group: ['transform'],
-		version: [1, 2, 2.1, 2.2],
+		version: [1, 2, 2.1, 2.2, 2.3],
 		description: 'Compare two inputs for changes',
 		defaults: { name: 'Compare Datasets' },
 		// eslint-disable-next-line n8n-nodes-base/node-class-description-inputs-wrong-regular-node
 		inputs: ['main', 'main'],
 		inputNames: ['Input A', 'Input B'],
+		forceInputNodeExecution: '={{ $version < 2.3 }}',
+		requiredInputs: '={{ $version < 2.3 ? undefined : 1 }}',
 		// eslint-disable-next-line n8n-nodes-base/node-class-description-outputs-wrong
 		outputs: ['main', 'main', 'main', 'main'],
 		outputNames: ['In A only', 'Same', 'Different', 'In B only'],

packages/nodes-base/nodes/CompareDatasets/test/node/workflow.compareDatasets.forceInputNodeExecution.json

@@ -0,0 +1,496 @@
+{
+	"name": "Compare Datasets Node Test",
+	"nodes": [
+		{
+			"parameters": {},
+			"id": "0312bddf-aae0-423c-9041-d54fb124934f",
+			"name": "When clicking \"Execute Workflow\"",
+			"type": "n8n-nodes-base.manualTrigger",
+			"typeVersion": 1,
+			"position": [480, 720]
+		},
+		{
+			"parameters": {
+				"jsCode": "return [\n  {\n    json: {\n      number: 0\n    }\n  },\n  {\n    json: {\n      number: 1\n    }\n  },\n  {\n    json: {\n      number: 2\n    }\n  }\n];"
+			},
+			"id": "0542886d-6ab2-4695-b686-2cd60729ba9a",
+			"name": "Code",
+			"type": "n8n-nodes-base.code",
+			"typeVersion": 1,
+			"position": [900, 640]
+		},
+		{
+			"parameters": {
+				"mergeByFields": {
+					"values": [
+						{
+							"field1": "number",
+							"field2": "number"
+						}
+					]
+				},
+				"options": {}
+			},
+			"id": "f3e5e43b-a3bf-46c7-acd7-ae3d7d19d9f9",
+			"name": "Compare Datasets 2.2 - Old",
+			"type": "n8n-nodes-base.compareDatasets",
+			"typeVersion": 2.2,
+			"position": [1260, 40]
+		},
+		{
+			"parameters": {
+				"jsCode": "return [\n  {\n    json: {\n      number: 0\n    }\n  },\n  {\n    json: {\n      number: 1,\n      k: 2,\n    }\n  },\n  {\n    json: {\n      number: 10\n    }\n  },\n  {\n    json: {\n      number: 11\n    }\n  },\n  {\n    json: {\n      number: 12\n    }\n  }\n];"
+			},
+			"id": "c62e90b3-f84a-48a5-94bf-3267a4c8b69e",
+			"name": "Code1",
+			"type": "n8n-nodes-base.code",
+			"typeVersion": 1,
+			"position": [900, 60]
+		},
+		{
+			"parameters": {
+				"jsCode": "return [\n  {\n    json: {\n      number: 0\n    }\n  },\n  {\n    json: {\n      number: 1,\n      k: 2,\n    }\n  },\n  {\n    json: {\n      number: 10\n    }\n  },\n  {\n    json: {\n      number: 11\n    }\n  },\n  {\n    json: {\n      number: 12\n    }\n  }\n];"
+			},
+			"id": "46320ca2-8e8e-4ecf-b4f6-5899807c1500",
+			"name": "Code2",
+			"type": "n8n-nodes-base.code",
+			"typeVersion": 1,
+			"position": [900, 840]
+		},
+		{
+			"parameters": {},
+			"id": "4ae12a83-5d3f-4d5b-845b-65c930d8ef5a",
+			"name": "Old - A only",
+			"type": "n8n-nodes-base.noOp",
+			"typeVersion": 1,
+			"position": [1520, -180]
+		},
+		{
+			"parameters": {},
+			"id": "d4f5fd94-4b46-4b8c-8b8a-073e8c32ad85",
+			"name": "New - A only",
+			"type": "n8n-nodes-base.noOp",
+			"typeVersion": 1,
+			"position": [1520, 440]
+		},
+		{
+			"parameters": {},
+			"id": "0939f79b-fd75-4d2f-b40b-50780114c3f2",
+			"name": "Old - Same",
+			"type": "n8n-nodes-base.noOp",
+			"typeVersion": 1,
+			"position": [1520, -40]
+		},
+		{
+			"parameters": {},
+			"id": "199ea52c-b30a-401d-a920-9db5c8e10d38",
+			"name": "Old - Different",
+			"type": "n8n-nodes-base.noOp",
+			"typeVersion": 1,
+			"position": [1520, 100]
+		},
+		{
+			"parameters": {},
+			"id": "1ebcb5bb-3061-47ef-8c79-847ae8bdb568",
+			"name": "Old - B only",
+			"type": "n8n-nodes-base.noOp",
+			"typeVersion": 1,
+			"position": [1520, 240]
+		},
+		{
+			"parameters": {},
+			"id": "38689dbf-49f2-4f3b-855b-abd821ec316f",
+			"name": "New - B only",
+			"type": "n8n-nodes-base.noOp",
+			"typeVersion": 1,
+			"position": [1520, 860]
+		},
+		{
+			"parameters": {},
+			"id": "dfcac903-95dc-4519-b49f-a6a65bf8fdb8",
+			"name": "New - Different",
+			"type": "n8n-nodes-base.noOp",
+			"typeVersion": 1,
+			"position": [1520, 720]
+		},
+		{
+			"parameters": {},
+			"id": "b8588ebc-4dc8-41f5-9a0a-64d151d7122e",
+			"name": "New - Same",
+			"type": "n8n-nodes-base.noOp",
+			"typeVersion": 1,
+			"position": [1520, 580]
+		},
+		{
+			"parameters": {
+				"jsCode": "return [\n  {\n    json: {\n      number: 0\n    }\n  },\n  {\n    json: {\n      number: 1,\n      k: 2,\n    }\n  },\n  {\n    json: {\n      number: 10\n    }\n  },\n  {\n    json: {\n      number: 11\n    }\n  },\n  {\n    json: {\n      number: 12\n    }\n  }\n];"
+			},
+			"id": "d35f3f52-c967-46e8-be3a-0bf709b20ef8",
+			"name": "Code3",
+			"type": "n8n-nodes-base.code",
+			"typeVersion": 1,
+			"position": [880, 1340]
+		},
+		{
+			"parameters": {},
+			"id": "75690ad6-c870-4950-9085-12fdd9c12ddd",
+			"name": "New - A only1",
+			"type": "n8n-nodes-base.noOp",
+			"typeVersion": 1,
+			"position": [1520, 1100]
+		},
+		{
+			"parameters": {},
+			"id": "9abb523f-349c-48b0-b36b-0c74064a6219",
+			"name": "New - B only1",
+			"type": "n8n-nodes-base.noOp",
+			"typeVersion": 1,
+			"position": [1520, 1520]
+		},
+		{
+			"parameters": {},
+			"id": "c4230d94-eaa6-420d-baff-288463722a03",
+			"name": "New - Different1",
+			"type": "n8n-nodes-base.noOp",
+			"typeVersion": 1,
+			"position": [1520, 1380]
+		},
+		{
+			"parameters": {},
+			"id": "58287181-dc90-4806-a053-83b3ef36e673",
+			"name": "New - Same1",
+			"type": "n8n-nodes-base.noOp",
+			"typeVersion": 1,
+			"position": [1520, 1240]
+		},
+		{
+			"parameters": {
+				"mergeByFields": {
+					"values": [
+						{
+							"field1": "number",
+							"field2": "number"
+						}
+					]
+				},
+				"options": {}
+			},
+			"id": "5514c636-ee64-45f3-8832-77ad6652cc08",
+			"name": "Compare Datasets 2.3 - New - Connected",
+			"type": "n8n-nodes-base.compareDatasets",
+			"typeVersion": 2.3,
+			"position": [1260, 1320]
+		},
+		{
+			"parameters": {
+				"mergeByFields": {
+					"values": [
+						{
+							"field1": "number",
+							"field2": "number"
+						}
+					]
+				},
+				"options": {}
+			},
+			"id": "a25f4766-9bb4-40a0-9ae2-ef0004f5938a",
+			"name": "Compare Datasets 2.3 - New - Not Connected",
+			"type": "n8n-nodes-base.compareDatasets",
+			"typeVersion": 2.3,
+			"position": [1260, 660]
+		}
+	],
+	"pinData": {
+		"Old - A only": [
+			{
+				"json": {
+					"number": 2
+				}
+			}
+		],
+		"Old - Same": [
+			{
+				"json": {
+					"number": 0
+				}
+			}
+		],
+		"Old - Different": [
+			{
+				"json": {
+					"keys": {
+						"number": 1
+					},
+					"same": {
+						"number": 1
+					},
+					"different": {
+						"k": {
+							"inputA": null,
+							"inputB": 2
+						}
+					}
+				}
+			}
+		],
+		"Old - B only": [
+			{
+				"json": {
+					"number": 10
+				}
+			},
+			{
+				"json": {
+					"number": 11
+				}
+			},
+			{
+				"json": {
+					"number": 12
+				}
+			}
+		],
+		"New - A only": [
+			{
+				"json": {
+					"number": 0
+				}
+			},
+			{
+				"json": {
+					"number": 1
+				}
+			},
+			{
+				"json": {
+					"number": 2
+				}
+			}
+		],
+		"New - A only1": [
+			{
+				"json": {
+					"number": 2
+				}
+			}
+		],
+		"New - Same1": [
+			{
+				"json": {
+					"number": 0
+				}
+			}
+		],
+		"New - Different1": [
+			{
+				"json": {
+					"keys": {
+						"number": 1
+					},
+					"same": {
+						"number": 1
+					},
+					"different": {
+						"k": {
+							"inputA": null,
+							"inputB": 2
+						}
+					}
+				}
+			}
+		],
+		"New - B only1": [
+			{
+				"json": {
+					"number": 10
+				}
+			},
+			{
+				"json": {
+					"number": 11
+				}
+			},
+			{
+				"json": {
+					"number": 12
+				}
+			}
+		]
+	},
+	"connections": {
+		"When clicking \"Execute Workflow\"": {
+			"main": [
+				[
+					{
+						"node": "Code",
+						"type": "main",
+						"index": 0
+					},
+					{
+						"node": "Code3",
+						"type": "main",
+						"index": 0
+					}
+				]
+			]
+		},
+		"Code": {
+			"main": [
+				[
+					{
+						"node": "Compare Datasets 2.3 - New - Not Connected",
+						"type": "main",
+						"index": 0
+					},
+					{
+						"node": "Compare Datasets 2.2 - Old",
+						"type": "main",
+						"index": 0
+					},
+					{
+						"node": "Compare Datasets 2.3 - New - Connected",
+						"type": "main",
+						"index": 0
+					}
+				]
+			]
+		},
+		"Code1": {
+			"main": [
+				[
+					{
+						"node": "Compare Datasets 2.2 - Old",
+						"type": "main",
+						"index": 1
+					}
+				]
+			]
+		},
+		"Code2": {
+			"main": [
+				[
+					{
+						"node": "Compare Datasets 2.3 - New - Not Connected",
+						"type": "main",
+						"index": 1
+					}
+				]
+			]
+		},
+		"Compare Datasets 2.2 - Old": {
+			"main": [
+				[
+					{
+						"node": "Old - A only",
+						"type": "main",
+						"index": 0
+					}
+				],
+				[
+					{
+						"node": "Old - Same",
+						"type": "main",
+						"index": 0
+					}
+				],
+				[
+					{
+						"node": "Old - Different",
+						"type": "main",
+						"index": 0
+					}
+				],
+				[
+					{
+						"node": "Old - B only",
+						"type": "main",
+						"index": 0
+					}
+				]
+			]
+		},
+		"Code3": {
+			"main": [
+				[
+					{
+						"node": "Compare Datasets 2.3 - New - Connected",
+						"type": "main",
+						"index": 1
+					}
+				]
+			]
+		},
+		"Compare Datasets 2.3 - New - Connected": {
+			"main": [
+				[
+					{
+						"node": "New - A only1",
+						"type": "main",
+						"index": 0
+					}
+				],
+				[
+					{
+						"node": "New - Same1",
+						"type": "main",
+						"index": 0
+					}
+				],
+				[
+					{
+						"node": "New - Different1",
+						"type": "main",
+						"index": 0
+					}
+				],
+				[
+					{
+						"node": "New - B only1",
+						"type": "main",
+						"index": 0
+					}
+				]
+			]
+		},
+		"Compare Datasets 2.3 - New - Not Connected": {
+			"main": [
+				[
+					{
+						"node": "New - A only",
+						"type": "main",
+						"index": 0
+					}
+				],
+				[
+					{
+						"node": "New - Same",
+						"type": "main",
+						"index": 0
+					}
+				],
+				[
+					{
+						"node": "New - Different",
+						"type": "main",
+						"index": 0
+					}
+				],
+				[
+					{
+						"node": "New - B only",
+						"type": "main",
+						"index": 0
+					}
+				]
+			]
+		}
+	},
+	"active": false,
+	"settings": {},
+	"versionId": "d5c0f040-7406-4e69-bd5d-a362a739c8d8",
+	"id": "1114",
+	"meta": {
+		"instanceId": "021d3c82ba2d3bc090cbf4fc81c9312668bcc34297e022bb3438c5c88a43a5ff"
+	},
+	"tags": []
+}

packages/nodes-base/nodes/Merge/Merge.node.ts

@@ -20,6 +20,7 @@ export class Merge extends VersionedNodeType {
 			1: new MergeV1(baseDescription),
 			2: new MergeV2(baseDescription),
 			2.1: new MergeV2(baseDescription),
+			2.2: new MergeV2(baseDescription),
 		};
 
 		super(nodeVersions, baseDescription);

packages/nodes-base/nodes/Merge/v1/MergeV1.node.ts

@@ -30,6 +30,7 @@ const versionDescription: INodeTypeDescription = {
 	inputs: ['main', 'main'],
 	outputs: ['main'],
 	inputNames: ['Input 1', 'Input 2'],
+	forceInputNodeExecution: true,
 	properties: [
 		oldVersionNotice,
 		{

packages/nodes-base/nodes/Merge/v2/MergeV2.node.ts

@@ -35,7 +35,7 @@ const versionDescription: INodeTypeDescription = {
 	name: 'merge',
 	icon: 'fa:code-branch',
 	group: ['transform'],
-	version: [2, 2.1],
+	version: [2, 2.1, 2.2],
 	subtitle: '={{$parameter["mode"]}}',
 	description: 'Merges data of multiple streams once data from both is available',
 	defaults: {
@@ -46,6 +46,11 @@ const versionDescription: INodeTypeDescription = {
 	inputs: ['main', 'main'],
 	outputs: ['main'],
 	inputNames: ['Input 1', 'Input 2'],
+	// If the node is of version 2.2 or if mode is chooseBranch data from both branches is required
+	// to continue, else data from any input suffices
+	requiredInputs:
+		'={{ $version < 2.2 ? undefined : ($parameter["mode"] === "chooseBranch" ? [0, 1] : 1) }}',
+	forceInputNodeExecution: '={{ $version < 2.2 }}',
 	properties: [
 		{
 			displayName: 'Mode',
@@ -374,6 +379,12 @@ export class MergeV2 implements INodeType {
 				let input1 = this.getInputData(0);
 				let input2 = this.getInputData(1);
 
+				if (input1.length === 0 || input2.length === 0) {
+					// If data of any input is missing, return the data of
+					// the input that contains data
+					return [[...input1, ...input2]];
+				}
+
 				if (clashHandling.resolveClash === 'preferInput1') {
 					[input1, input2] = [input2, input1];
 				}
@@ -454,6 +465,7 @@ export class MergeV2 implements INodeType {
 
 				let input1 = this.getInputData(0);
 				let input2 = this.getInputData(1);
+
 				if (nodeVersion < 2.1) {
 					input1 = checkInput(
 						this.getInputData(0),
@@ -473,6 +485,24 @@ export class MergeV2 implements INodeType {
 					if (!input1) return [returnData];
 				}
 
+				if (input1.length === 0 || input2.length === 0) {
+					if (joinMode === 'keepMatches') {
+						// Stop the execution
+						return [[]];
+					} else if (joinMode === 'enrichInput1' && input1.length === 0) {
+						// No data to enrich so stop
+						return [[]];
+					} else if (joinMode === 'enrichInput2' && input2.length === 0) {
+						// No data to enrich so stop
+						return [[]];
+					} else {
+						// Return the data of any of the inputs that contains data
+						return [[...input1, ...input2]];
+					}
+				}
+
+				if (!input1) return [returnData];
+
 				if (!input2 || !matchFields.length) {
 					if (
 						joinMode === 'keepMatches' ||

packages/workflow/src/Expression.ts

@@ -358,8 +358,8 @@ export class Expression {
 		timezone: string,
 		additionalKeys: IWorkflowDataProxyAdditionalKeys,
 		executeData?: IExecuteData,
-		defaultValue?: boolean | number | string,
-	): boolean | number | string | undefined {
+		defaultValue?: boolean | number | string | unknown[],
+	): boolean | number | string | undefined | unknown[] {
 		if (parameterValue === undefined) {
 			// Value is not set so return the default
 			return defaultValue;

packages/workflow/src/Interfaces.ts

@@ -1429,6 +1429,8 @@ export interface INodeTypeDescription extends INodeTypeBaseDescription {
 	eventTriggerDescription?: string;
 	activationMessage?: string;
 	inputs: string[];
+	forceInputNodeExecution?: string | boolean; // TODO: This option should be deprecated after a while
+	requiredInputs?: string | number[] | number;
 	inputNames?: string[];
 	outputs: string[];
 	outputNames?: string[];

packages/workflow/src/Workflow.ts

@@ -1186,11 +1186,35 @@ export class Workflow {
 			// because then it is a trigger node. As they only pass data through and so the input-data
 			// becomes output-data it has to be possible.
 
-			if (inputData.hasOwnProperty('main') && inputData.main.length > 0) {
+			if (inputData.main?.length > 0) {
 				// We always use the data of main input and the first input for execute
 				connectionInputData = inputData.main[0] as INodeExecutionData[];
 			}
 
+			let forceInputNodeExecution = nodeType.description.forceInputNodeExecution;
+			if (forceInputNodeExecution !== undefined) {
+				if (typeof forceInputNodeExecution === 'string') {
+					forceInputNodeExecution = !!this.expression.getSimpleParameterValue(
+						node,
+						forceInputNodeExecution,
+						mode,
+						additionalData.timezone,
+						{ $version: node.typeVersion },
+					);
+				}
+
+				if (!forceInputNodeExecution) {
+					// If the nodes do not get force executed data of some inputs may be missing
+					// for that reason do we use the data of the first one that contains any
+					for (const mainData of inputData.main) {
+						if (mainData?.length) {
+							connectionInputData = mainData;
+							break;
+						}
+					}
+				}
+			}
+
 			if (connectionInputData.length === 0) {
 				// No data for node so return
 				return { data: undefined };