fix(MySQL Node): Support "Continue on Error" for connection-related errors (#25032)

packages/nodes-base/nodes/MySql/test/v2/mysql.integration.test.ts

@@ -101,9 +101,7 @@ describe('MySQL Integration - NODE-4174', () => {
 		expect(result[0][0].json).toHaveProperty('message');
 	});
 
-	// NODE-4174: createPool() is outside try-catch, so connection errors bypass continueOnFail.
-	// Remove .fails when fixed.
-	test.fails('bug: connection error should return error item with continueOnFail', async () => {
+	test('connection error should return error item with continueOnFail', async () => {
 		const params = {
 			resource: 'database',
 			operation: 'executeQuery',

packages/nodes-base/nodes/MySql/test/v2/runQueries.test.ts

@@ -207,4 +207,40 @@ describe('Test MySql V2, runQueries', () => {
 
 		expect(connectionReleaseSpy).toBeCalledTimes(1);
 	});
+
+	it('should return error item with continueOnFail = true for connection error', async () => {
+		const nodeOptions: IDataObject = { queryBatching: BATCH_MODE.SINGLE, nodeVersion: 2 };
+		const pool = createFakePool(fakeConnection);
+		pool.getConnection = jest.fn(() => {
+			throw new Error('ECONNREFUSED');
+		});
+		const fakeExecuteFunction = createMockExecuteFunction({}, mySqlMockNode);
+		fakeExecuteFunction.continueOnFail = () => true;
+
+		const result = await configureQueryRunner.call(
+			fakeExecuteFunction,
+			nodeOptions,
+			pool,
+		)([{ query: 'SELECT * FROM my_table WHERE id = ?', values: [55] }]);
+
+		expect(result).toEqual([{ json: expect.objectContaining({ message: 'Connection refused' }) }]);
+	});
+
+	it('should throw error when continueOnFail = false for connection error', async () => {
+		const nodeOptions: IDataObject = { queryBatching: BATCH_MODE.SINGLE, nodeVersion: 2 };
+		const pool = createFakePool(fakeConnection);
+		pool.getConnection = jest.fn(() => {
+			throw new Error('ECONNREFUSED');
+		});
+		const fakeExecuteFunction = createMockExecuteFunction({}, mySqlMockNode);
+		fakeExecuteFunction.continueOnFail = () => false;
+
+		await expect(
+			configureQueryRunner.call(
+				fakeExecuteFunction,
+				nodeOptions,
+				pool,
+			)([{ query: 'SELECT * FROM my_table WHERE id = ?', values: [55] }]),
+		).rejects.toThrow('Connection refused');
+	});
 });

packages/nodes-base/nodes/MySql/v2/helpers/interfaces.ts

@@ -4,6 +4,7 @@ import type { IDataObject, INodeExecutionData, SSHCredentials } from 'n8n-workfl
 export type Mysql2Connection = mysql2.Connection;
 export type Mysql2Pool = mysql2.Pool;
 export type Mysql2OkPacket = mysql2.OkPacket;
+export type Mysql2PoolConnection = mysql2.PoolConnection;
 
 export type QueryValues = Array<string | number | IDataObject>;
 export type QueryWithValues = { query: string; values: QueryValues };

packages/nodes-base/nodes/MySql/v2/helpers/utils.ts

@@ -10,6 +10,7 @@ import { NodeOperationError } from 'n8n-workflow';
 
 import type {
 	Mysql2Pool,
+	Mysql2PoolConnection,
 	ParameterMatch,
 	QueryMode,
 	QueryValues,
@@ -320,7 +321,17 @@ export function configureQueryRunner(
 		let returnData: INodeExecutionData[] = [];
 		const mode = (options.queryBatching as QueryMode) || BATCH_MODE.SINGLE;
 
-		const connection = await pool.getConnection();
+		let connection: Mysql2PoolConnection;
+		try {
+			connection = await pool.getConnection();
+		} catch (e) {
+			const error = parseMySqlError.call(this, e);
+			if (!this.continueOnFail()) {
+				throw error;
+			}
+
+			return [{ json: { message: error.message, error: { ...error } } }];
+		}
 
 		if (mode === BATCH_MODE.SINGLE) {
 			const formattedQueries = queries.map(({ query, values }) => connection.format(query, values));
@@ -533,7 +544,7 @@ export function addWhereClauses(
 		}${valueReplacement}${operator}`;
 	});
 
-	return [`${query}${whereQuery}`, replacements.concat(...values)];
+	return [`${query}${whereQuery}`, replacements.concat.apply(replacements, values)];
 }
 
 export function addSortRules(
@@ -552,7 +563,7 @@ export function addSortRules(
 		orderByQuery += ` ${escapeSqlIdentifier(rule.column)} ${direction}${endWith}`;
 	});
 
-	return [`${query}${orderByQuery}`, replacements.concat(...values)];
+	return [`${query}${orderByQuery}`, replacements.concat.apply(replacements, values)];
 }
 
 export function replaceEmptyStringsByNulls(