fix(core): Fix task runner logging to browser console (#15111)

packages/@n8n/task-runner/src/js-task-runner/js-task-runner.ts

@@ -1,7 +1,14 @@
+import { isObject } from 'lodash';
 import set from 'lodash/set';
 import { DateTime, Duration, Interval } from 'luxon';
 import { getAdditionalKeys } from 'n8n-core';
-import { WorkflowDataProxy, Workflow, ObservableObject, Expression } from 'n8n-workflow';
+import {
+	WorkflowDataProxy,
+	Workflow,
+	ObservableObject,
+	Expression,
+	jsonStringify,
+} from 'n8n-workflow';
 import type {
 	CodeExecutionMode,
 	IWorkflowExecuteAdditionalData,
@@ -19,7 +26,6 @@ import type {
 	IWorkflowDataProxyData,
 } from 'n8n-workflow';
 import * as a from 'node:assert';
-import { inspect } from 'node:util';
 import { type Context, createContext, runInContext } from 'node:vm';
 
 import type { MainConfig } from '@/config/main-config';
@@ -498,7 +504,11 @@ export class JsTaskRunner extends TaskRunner {
 			// Send log output back to the main process. It will take care of forwarding
 			// it to the UI or printing to console.
 			log: (...args: unknown[]) => {
-				const formattedLogArgs = args.map((arg) => inspect(arg));
+				const formattedLogArgs = args.map((arg) => {
+					if (isObject(arg) && '__isExecutionContext' in arg) return '[[ExecutionContext]]';
+					if (typeof arg === 'string') return `'${arg}'`;
+					return jsonStringify(arg, { replaceCircularRefs: true });
+				});
 				void this.makeRpcCall(taskId, 'logNodeOutput', formattedLogArgs);
 			},
 		};
@@ -521,7 +531,7 @@ export class JsTaskRunner extends TaskRunner {
 		additionalProperties: Record<string, unknown> = {},
 	): Context {
 		return createContext({
-			[inspect.custom]: () => '[[ExecutionContext]]',
+			__isExecutionContext: true,
 			require: this.requireResolver,
 			module: {},
 			console: this.buildCustomConsole(taskId),

packages/core/src/execution-engine/node-execution-context/__tests__/execute-context.test.ts

@@ -226,4 +226,37 @@ describe('ExecuteContext', () => {
 			]);
 		});
 	});
+
+	describe('logNodeOutput', () => {
+		it('when in manual mode, should parse JSON', () => {
+			const json = '{"key": "value", "nested": {"foo": "bar"}}';
+			const expectedParsedObject = { key: 'value', nested: { foo: 'bar' } };
+			const numberArg = 42;
+			const stringArg = 'hello world!';
+
+			const manualModeContext = new ExecuteContext(
+				workflow,
+				node,
+				additionalData,
+				'manual',
+				runExecutionData,
+				runIndex,
+				connectionInputData,
+				inputData,
+				executeData,
+				[closeFn],
+				abortSignal,
+			);
+
+			const sendMessageSpy = jest.spyOn(manualModeContext, 'sendMessageToUI');
+
+			manualModeContext.logNodeOutput(json, numberArg, stringArg);
+
+			expect(sendMessageSpy.mock.calls[0][0]).toEqual(expectedParsedObject);
+			expect(sendMessageSpy.mock.calls[0][1]).toBe(numberArg);
+			expect(sendMessageSpy.mock.calls[0][2]).toBe(stringArg);
+
+			sendMessageSpy.mockRestore();
+		});
+	});
 });

packages/core/src/execution-engine/node-execution-context/execute-context.ts

@@ -20,6 +20,7 @@ import {
 	ApplicationError,
 	createDeferredPromise,
 	createEnvProviderState,
+	jsonParse,
 	NodeConnectionTypes,
 } from 'n8n-workflow';
 
@@ -183,7 +184,10 @@ export class ExecuteContext extends BaseExecuteContext implements IExecuteFuncti
 
 	logNodeOutput(...args: unknown[]): void {
 		if (this.mode === 'manual') {
-			this.sendMessageToUI(...args);
+			const parsedLogArgs = args.map((arg) =>
+				typeof arg === 'string' ? jsonParse(arg, { fallbackValue: arg }) : arg,
+			);
+			this.sendMessageToUI(...parsedLogArgs);
 			return;
 		}