fix(core): Prevent workflow history saving error from happening (#7812)

When performing actions such as renaming a workflow or updating its
settings, n8n errors with "Failed to save workflow version" in the
console although the saving process was successful. We are now correctly
checking whether `nodes` and `connections` exist and only then save a
snapshot.

Github issue / Community forum post (link here to close automatically):

packages/cli/test/unit/services/workflowHistory.service.ee.test.ts

@@ -0,0 +1,114 @@
+import { User } from '@db/entities/User';
+import { WorkflowHistoryRepository } from '@db/repositories/workflowHistory.repository';
+import { SharedWorkflowRepository } from '@db/repositories/sharedWorkflow.repository';
+import { WorkflowHistoryService } from '@/workflows/workflowHistory/workflowHistory.service.ee';
+import { mockInstance } from '../../shared/mocking';
+import { Logger } from '@/Logger';
+import { getWorkflow } from '../WorkflowHelpers.test';
+import { mockClear } from 'jest-mock-extended';
+
+const workflowHistoryRepository = mockInstance(WorkflowHistoryRepository);
+const logger = mockInstance(Logger);
+const sharedWorkflowRepository = mockInstance(SharedWorkflowRepository);
+const workflowHistoryService = new WorkflowHistoryService(
+	logger,
+	workflowHistoryRepository,
+	sharedWorkflowRepository,
+);
+const testUser = Object.assign(new User(), {
+	id: '1234',
+	password: 'passwordHash',
+	mfaEnabled: false,
+	firstName: 'John',
+	lastName: 'Doe',
+});
+let isWorkflowHistoryEnabled = true;
+
+jest.mock('@/workflows/workflowHistory/workflowHistoryHelper.ee', () => {
+	return {
+		isWorkflowHistoryEnabled: jest.fn(() => isWorkflowHistoryEnabled),
+	};
+});
+
+describe('WorkflowHistoryService', () => {
+	beforeEach(() => {
+		mockClear(workflowHistoryRepository.insert);
+	});
+
+	describe('saveVersion', () => {
+		it('should save a new version when workflow history is enabled and nodes and connections are present', async () => {
+			// Arrange
+			isWorkflowHistoryEnabled = true;
+			const workflow = getWorkflow({ addNodeWithoutCreds: true });
+			const workflowId = '123';
+			workflow.connections = {};
+			workflow.id = workflowId;
+			workflow.versionId = '456';
+
+			// Act
+			await workflowHistoryService.saveVersion(testUser, workflow, workflowId);
+
+			// Assert
+			expect(workflowHistoryRepository.insert).toHaveBeenCalledWith({
+				authors: 'John Doe',
+				connections: {},
+				nodes: workflow.nodes,
+				versionId: workflow.versionId,
+				workflowId,
+			});
+		});
+
+		it('should not save a new version when workflow history is disabled', async () => {
+			// Arrange
+			isWorkflowHistoryEnabled = false;
+			const workflow = getWorkflow({ addNodeWithoutCreds: true });
+			const workflowId = '123';
+			workflow.connections = {};
+			workflow.id = workflowId;
+			workflow.versionId = '456';
+
+			// Act
+			await workflowHistoryService.saveVersion(testUser, workflow, workflowId);
+
+			// Assert
+			expect(workflowHistoryRepository.insert).not.toHaveBeenCalled();
+		});
+
+		it('should not save a new version when nodes or connections are missing', async () => {
+			// Arrange
+			isWorkflowHistoryEnabled = true;
+			const workflow = getWorkflow({ addNodeWithoutCreds: true });
+			const workflowId = '123';
+			workflow.id = workflowId;
+			workflow.versionId = '456';
+			// Nodes are set but connections is empty
+
+			// Act
+			await workflowHistoryService.saveVersion(testUser, workflow, workflowId);
+
+			// Assert
+			expect(workflowHistoryRepository.insert).not.toHaveBeenCalled();
+		});
+
+		it('should log an error when failed to save workflow history version', async () => {
+			// Arrange
+			isWorkflowHistoryEnabled = true;
+			const workflow = getWorkflow({ addNodeWithoutCreds: true });
+			const workflowId = '123';
+			workflow.connections = {};
+			workflow.id = workflowId;
+			workflow.versionId = '456';
+			workflowHistoryRepository.insert.mockRejectedValueOnce(new Error('Test error'));
+
+			// Act
+			await workflowHistoryService.saveVersion(testUser, workflow, workflowId);
+
+			// Assert
+			expect(workflowHistoryRepository.insert).toHaveBeenCalled();
+			expect(logger.error).toHaveBeenCalledWith(
+				'Failed to save workflow history version for workflow 123',
+				expect.any(Error),
+			);
+		});
+	});
+});