fix(core): Validate task runner mode (#14376)

packages/@n8n/config/package.json

@@ -22,7 +22,8 @@
   ],
   "dependencies": {
     "@n8n/di": "workspace:*",
-    "reflect-metadata": "catalog:"
+    "reflect-metadata": "catalog:",
+    "zod": "catalog:"
   },
   "devDependencies": {
     "@n8n/typescript-config": "workspace:*"

packages/@n8n/config/src/configs/runners.config.ts

@@ -1,18 +1,21 @@
+import { z } from 'zod';
+
 import { Config, Env } from '../decorators';
 
-/**
- * Whether to enable task runners and how to run them
- * - internal: Task runners are run as a child process and launched by n8n
- * - external: Task runners are run as a separate program not launched by n8n
- */
-export type TaskRunnerMode = 'internal' | 'external';
+const runnerModeSchema = z.enum(['internal', 'external']);
+
+export type TaskRunnerMode = z.infer<typeof runnerModeSchema>;
 
 @Config
 export class TaskRunnersConfig {
 	@Env('N8N_RUNNERS_ENABLED')
 	enabled: boolean = false;
 
-	@Env('N8N_RUNNERS_MODE')
+	/**
+	 * Whether the task runner should run as a child process spawned by n8n (internal mode)
+	 * or as a separate process launched outside n8n (external mode).
+	 */
+	@Env('N8N_RUNNERS_MODE', runnerModeSchema)
 	mode: TaskRunnerMode = 'internal';
 
 	/** Endpoint which task runners connect to */

packages/@n8n/config/src/decorators.ts

@@ -1,6 +1,7 @@
 import 'reflect-metadata';
 import { Container, Service } from '@n8n/di';
 import { readFileSync } from 'fs';
+import { z } from 'zod';
 
 // eslint-disable-next-line @typescript-eslint/ban-types
 type Class = Function;
@@ -10,6 +11,7 @@ type PropertyType = number | boolean | string | Class;
 interface PropertyMetadata {
 	type: PropertyType;
 	envName?: string;
+	schema?: z.ZodType<unknown>;
 }
 
 const globalMetadata = new Map<Class, Map<PropertyKey, PropertyMetadata>>();
@@ -33,14 +35,22 @@ export const Config: ClassDecorator = (ConfigClass: Class) => {
 			throw new Error('Invalid config class: ' + ConfigClass.name);
 		}
 
-		for (const [key, { type, envName }] of classMetadata) {
+		for (const [key, { type, envName, schema }] of classMetadata) {
 			if (typeof type === 'function' && globalMetadata.has(type)) {
 				config[key] = Container.get(type as Constructable);
 			} else if (envName) {
 				const value = readEnv(envName);
 				if (value === undefined) continue;
 
-				if (type === Number) {
+				if (schema) {
+					const result = schema.safeParse(value);
+					if (result.error) {
+						console.warn(
+							`Invalid value for ${envName} - ${result.error.issues[0].message}. Falling back to default value.`,
+						);
+						continue;
+					}
+				} else if (type === Number) {
 					const parsed = Number(value);
 					if (isNaN(parsed)) {
 						console.warn(`Invalid number value for ${envName}: ${value}`);
@@ -84,18 +94,21 @@ export const Nested: PropertyDecorator = (target: object, key: PropertyKey) => {
 };
 
 export const Env =
-	(envName: string): PropertyDecorator =>
+	(envName: string, schema?: PropertyMetadata['schema']): PropertyDecorator =>
 	(target: object, key: PropertyKey) => {
 		const ConfigClass = target.constructor;
 		const classMetadata =
 			globalMetadata.get(ConfigClass) ?? new Map<PropertyKey, PropertyMetadata>();
+
 		const type = Reflect.getMetadata('design:type', target, key) as PropertyType;
-		if (type === Object) {
+		const isEnum = schema instanceof z.ZodEnum;
+		if (type === Object && !isEnum) {
 			// eslint-disable-next-line n8n-local-rules/no-plain-errors
 			throw new Error(
 				`Invalid decorator metadata on key "${key as string}" on ${ConfigClass.name}\n Please use explicit typing on all config fields`,
 			);
 		}
-		classMetadata.set(key, { type, envName });
+
+		classMetadata.set(key, { type, envName, schema });
 		globalMetadata.set(ConfigClass, classMetadata);
 	};

packages/@n8n/config/test/config.test.ts

@@ -399,4 +399,20 @@ describe('GlobalConfig', () => {
 			'Invalid number value for DB_LOGGING_MAX_EXECUTION_TIME: abcd',
 		);
 	});
+
+	describe('string unions', () => {
+		it('on invalid value, should warn and fall back to default value', () => {
+			process.env = {
+				N8N_RUNNERS_MODE: 'non-existing-mode',
+			};
+
+			const globalConfig = Container.get(GlobalConfig);
+			expect(globalConfig.taskRunners.mode).toEqual('internal');
+			expect(consoleWarnMock).toHaveBeenCalledWith(
+				expect.stringContaining(
+					"Invalid value for N8N_RUNNERS_MODE - Invalid enum value. Expected 'internal' | 'external', received 'non-existing-mode'. Falling back to default value.",
+				),
+			);
+		});
+	});
 });

pnpm-lock.yaml

@@ -396,6 +396,9 @@ importers:
       reflect-metadata:
         specifier: 'catalog:'
         version: 0.2.2
+      zod:
+        specifier: 'catalog:'
+        version: 3.24.1
     devDependencies:
       '@n8n/typescript-config':
         specifier: workspace:*