fix(editor): Fix trimPayloadToSize mutating original objects in AI assistant (#17498)

packages/frontend/editor-ui/src/composables/useAIAssistantHelpers.test.ts

@@ -1,5 +1,10 @@
 import { describe, it, expect } from 'vitest';
-import type { INode, IRunExecutionData, NodeConnectionType } from 'n8n-workflow';
+import {
+	deepCopy,
+	type INode,
+	type IRunExecutionData,
+	type NodeConnectionType,
+} from 'n8n-workflow';
 import { useAIAssistantHelpers } from './useAIAssistantHelpers';
 import { createTestingPinia } from '@pinia/testing';
 import { setActivePinia } from 'pinia';
@@ -569,7 +574,7 @@ describe('Trim Payload Size', () => {
 	});
 
 	it('Should trim active node parameters in error helper payload', () => {
-		const payload = ERROR_HELPER_TEST_PAYLOAD;
+		const payload = deepCopy(ERROR_HELPER_TEST_PAYLOAD);
 		aiAssistantHelpers.trimPayloadSize(payload);
 		expect((payload.payload as ChatRequest.InitErrorHelper).node.parameters).toEqual({});
 	});
@@ -577,15 +582,18 @@ describe('Trim Payload Size', () => {
 	it('Should trim all node parameters in support chat', () => {
 		// Testing the scenario where only one trimming pass is needed
 		// (payload is under the limit after removing all node parameters and execution data)
-		const payload: ChatRequest.RequestPayload = SUPPORT_CHAT_TEST_PAYLOAD;
-		const supportPayload: ChatRequest.InitSupportChat =
-			payload.payload as ChatRequest.InitSupportChat;
+		const payload: ChatRequest.RequestPayload = deepCopy(SUPPORT_CHAT_TEST_PAYLOAD);
 
 		// Trimming to 4kb should be successful
 		expect(() =>
 			aiAssistantHelpers.trimPayloadSize(payload, PAYLOAD_SIZE_FOR_1_PASS),
 		).not.toThrow();
-		// All active node parameters should be removed
+
+		// Get the modified payload
+		const supportPayload: ChatRequest.InitSupportChat =
+			payload.payload as ChatRequest.InitSupportChat;
+
+		// All active node parameters should be removed in the payload
 		expect(supportPayload?.context?.activeNodeInfo?.node?.parameters).toEqual({});
 		// Also, all node parameters in the workflow should be removed
 		supportPayload.context?.currentWorkflow?.nodes?.forEach((node) => {
@@ -606,14 +614,17 @@ describe('Trim Payload Size', () => {
 	it('Should trim the whole context in support chat', () => {
 		// Testing the scenario where both trimming passes are needed
 		// (payload is over the limit after removing all node parameters and execution data)
-		const payload: ChatRequest.RequestPayload = SUPPORT_CHAT_TEST_PAYLOAD;
-		const supportPayload: ChatRequest.InitSupportChat =
-			payload.payload as ChatRequest.InitSupportChat;
+		const payload: ChatRequest.RequestPayload = deepCopy(SUPPORT_CHAT_TEST_PAYLOAD);
 
 		// Trimming should be successful
 		expect(() =>
 			aiAssistantHelpers.trimPayloadSize(payload, PAYLOAD_SIZE_FOR_2_PASSES),
 		).not.toThrow();
+
+		// Get the modified payload
+		const supportPayload: ChatRequest.InitSupportChat =
+			payload.payload as ChatRequest.InitSupportChat;
+
 		// The whole context object should be removed
 		expect(supportPayload.context).not.toBeDefined();
 	});
@@ -622,4 +633,111 @@ describe('Trim Payload Size', () => {
 		const payload = ERROR_HELPER_TEST_PAYLOAD;
 		expect(() => aiAssistantHelpers.trimPayloadSize(payload, 0.2)).toThrow();
 	});
+
+	it('Should NOT modify the original objects when trimming payload', () => {
+		// Create a test payload to verify that the original objects are not mutated
+		const testNode = {
+			id: 'test-node',
+			name: 'Test Node',
+			type: 'test.node',
+			typeVersion: 1,
+			position: [0, 0] as [number, number],
+			parameters: { key: 'value', nested: { data: 'test' } },
+		};
+
+		const workflowNode = {
+			id: 'workflow-node',
+			name: 'Workflow Node',
+			type: 'test.node',
+			typeVersion: 1,
+			position: [100, 100] as [number, number],
+			parameters: { param1: 'test1', param2: 'test2' },
+		};
+
+		const errorNode = {
+			id: 'error-node',
+			name: 'Error Node',
+			type: 'test.node',
+			typeVersion: 1,
+			position: [200, 200] as [number, number],
+			parameters: { errorParam: 'errorValue' },
+		};
+
+		const payload: ChatRequest.RequestPayload = {
+			sessionId: 'test-session',
+			payload: {
+				type: 'init-support-chat',
+				role: 'user',
+				user: {
+					firstName: 'Test User',
+				},
+				question: 'test question',
+				context: {
+					activeNodeInfo: {
+						node: testNode,
+					},
+					currentWorkflow: {
+						name: 'Test Workflow',
+						nodes: [workflowNode],
+						connections: {},
+						active: false,
+					},
+					executionData: {
+						runData: {
+							'Test Node': [
+								{
+									startTime: 1000,
+									executionTime: 100,
+									executionIndex: 0,
+									source: [],
+									executionStatus: 'success',
+									data: { main: [[{ json: {} }]] },
+								},
+							],
+						},
+					},
+				},
+			},
+		};
+
+		// Create a shared reference to verify immutability
+		const sharedReference = {
+			activeNode: testNode,
+			workflowNode,
+			errorNode,
+		};
+
+		// Store original parameter values
+		const originalTestNodeParams = { ...testNode.parameters };
+		const originalWorkflowNodeParams = { ...workflowNode.parameters };
+		const originalErrorNodeParams = { ...errorNode.parameters };
+
+		// Verify parameters exist before trimming
+		expect(Object.keys(testNode.parameters).length).toBeGreaterThan(0);
+		expect(Object.keys(workflowNode.parameters).length).toBeGreaterThan(0);
+		expect(Object.keys(errorNode.parameters).length).toBeGreaterThan(0);
+
+		// Call trimPayloadSize
+		aiAssistantHelpers.trimPayloadSize(payload, PAYLOAD_SIZE_FOR_1_PASS);
+
+		// Check that the original objects have NOT been modified
+		expect(testNode.parameters).toEqual(originalTestNodeParams);
+		expect(workflowNode.parameters).toEqual(originalWorkflowNodeParams);
+		expect(errorNode.parameters).toEqual(originalErrorNodeParams);
+
+		// The shared references should also remain unchanged
+		expect(sharedReference.activeNode.parameters).toEqual(originalTestNodeParams);
+		expect(sharedReference.workflowNode.parameters).toEqual(originalWorkflowNodeParams);
+		expect(sharedReference.errorNode.parameters).toEqual(originalErrorNodeParams);
+
+		// But the payload itself should have been modified with empty parameters
+		const supportPayload = payload.payload as ChatRequest.InitSupportChat;
+		expect(supportPayload.context?.activeNodeInfo?.node?.parameters).toEqual({});
+		expect(
+			supportPayload.context?.currentWorkflow?.nodes?.every(
+				(node) => Object.keys(node.parameters).length === 0,
+			),
+		).toBe(true);
+		expect(supportPayload.context?.executionData?.runData).toEqual({});
+	});
 });

packages/frontend/editor-ui/src/composables/useAIAssistantHelpers.ts

@@ -265,7 +265,10 @@ export const useAIAssistantHelpers = () => {
 		payload: ChatRequest.RequestPayload,
 		size = AI_ASSISTANT_MAX_CONTENT_LENGTH,
 	): void => {
-		const requestPayload = payload.payload;
+		// Create a deep copy to avoid mutating the original payload
+		const payloadCopy = deepCopy(payload);
+		const requestPayload = payloadCopy.payload;
+
 		// For support chat, remove parameters from the active node object and all nodes in the workflow
 		if (requestPayload.type === 'init-support-chat') {
 			if (requestPayload.context?.activeNodeInfo?.node) {
@@ -288,7 +291,7 @@ export const useAIAssistantHelpers = () => {
 				}
 			}
 			// If the payload is still too big, remove the whole context object
-			if (getRequestPayloadSize(payload) > size) {
+			if (getRequestPayloadSize(payloadCopy) > size) {
 				requestPayload.context = undefined;
 			}
 			// For error helper, remove parameters from the active node object
@@ -297,9 +300,12 @@ export const useAIAssistantHelpers = () => {
 			requestPayload.node.parameters = {};
 		}
 		// If the payload is still too big, throw an error that will be shown to the user
-		if (getRequestPayloadSize(payload) > size) {
+		if (getRequestPayloadSize(payloadCopy) > size) {
 			throw new Error(locale.baseText('aiAssistant.payloadTooBig.message'));
 		}
+
+		// Apply the trimmed payload back to the original object
+		payload.payload = payloadCopy.payload;
 	};
 
 	/**