fix(n8n Form Node): Resolve expressions in HTML fields

packages/nodes-base/nodes/Form/Form.node.ts

@@ -336,15 +336,7 @@ export class Form extends Node {
 				});
 			}
 		} else {
-			fields = (context.getNodeParameter('formFields.values', []) as FormFieldsParameter).map(
-				(field) => {
-					if (field.fieldType === 'hiddenField') {
-						field.fieldLabel = field.fieldName as string;
-					}
-
-					return field;
-				},
-			);
+			fields = context.getNodeParameter('formFields.values', []) as FormFieldsParameter;
 		}
 
 		const method = context.getRequestObject().method;

packages/nodes-base/nodes/Form/formNodeUtils.ts

@@ -6,7 +6,7 @@ import {
 	type IWebhookResponseData,
 } from 'n8n-workflow';
 
-import { renderForm, sanitizeHtml } from './utils';
+import { renderForm } from './utils';
 
 export const renderFormNode = async (
 	context: IWebhookFunctions,
@@ -42,12 +42,6 @@ export const renderFormNode = async (
 			) as string) || 'Submit';
 	}
 
-	for (const field of fields) {
-		if (field.fieldType === 'html') {
-			field.html = sanitizeHtml(field.html as string);
-		}
-	}
-
 	const appendAttribution = context.evaluateExpression(
 		`{{ $('${trigger?.name}').params.options?.appendAttribution === false ? false : true }}`,
 	) as boolean;

packages/nodes-base/nodes/Form/test/formNodeUtils.test.ts

@@ -1,4 +1,5 @@
 import { type Response } from 'express';
+import type { MockProxy } from 'jest-mock-extended';
 import { mock } from 'jest-mock-extended';
 import {
 	type FormFieldsParameter,
@@ -9,10 +10,19 @@ import {
 import { renderFormNode } from '../formNodeUtils';
 
 describe('formNodeUtils', () => {
+	let webhookFunctions: MockProxy<IWebhookFunctions>;
+
+	beforeEach(() => {
+		webhookFunctions = mock<IWebhookFunctions>();
+	});
+
+	afterEach(() => {
+		jest.clearAllMocks();
+	});
+
 	it('should sanitize custom html', async () => {
-		const executeFunctions = mock<IWebhookFunctions>();
-		executeFunctions.getNode.mockReturnValue({ typeVersion: 2.1 } as any);
-		executeFunctions.getNodeParameter.calledWith('options').mockReturnValue({
+		webhookFunctions.getNode.mockReturnValue({ typeVersion: 2.1 } as any);
+		webhookFunctions.getNodeParameter.calledWith('options').mockReturnValue({
 			formTitle: 'Test Title',
 			formDescription: 'Test Description',
 			buttonLabel: 'Test Button Label',
@@ -47,12 +57,12 @@ describe('formNodeUtils', () => {
 			},
 		];
 
-		executeFunctions.getNodeParameter.calledWith('formFields.values').mockReturnValue(formFields);
+		webhookFunctions.getNodeParameter.calledWith('formFields.values').mockReturnValue(formFields);
 
 		const responseMock = mock<Response>({ render: mockRender } as any);
 		const triggerMock = mock<NodeTypeAndVersion>({ name: 'triggerName' } as any);
 
-		await renderFormNode(executeFunctions, responseMock, triggerMock, formFields, 'test');
+		await renderFormNode(webhookFunctions, responseMock, triggerMock, formFields, 'test');
 
 		expect(mockRender).toHaveBeenCalledWith('form-trigger', {
 			appendAttribution: true,

packages/nodes-base/nodes/Form/test/utils.test.ts

@@ -17,6 +17,7 @@ import {
 	isFormConnected,
 	sanitizeHtml,
 	validateResponseModeConfiguration,
+	prepareFormFields,
 } from '../utils';
 
 describe('FormTrigger, parseFormDescription', () => {
@@ -994,4 +995,40 @@ describe('validateResponseModeConfiguration', () => {
 
 		expect(() => validateResponseModeConfiguration(webhookFunctions)).not.toThrow();
 	});
+
+	describe('prepareFormFields', () => {
+		it('should resolve expressions in html fields', async () => {
+			webhookFunctions.evaluateExpression.mockImplementation((expression) => {
+				if (expression === '{{ $json.formMode }}') {
+					return 'Title';
+				}
+			});
+
+			const result = prepareFormFields(webhookFunctions, [
+				{
+					fieldLabel: 'Custom HTML',
+					fieldType: 'html',
+					elementName: 'test',
+					html: '<h1>{{ $json.formMode }}</h1>',
+				},
+			]);
+
+			expect(result[0].html).toBe('<h1>Title</h1>');
+		});
+		it('should prepare hiddenField', async () => {
+			const result = prepareFormFields(webhookFunctions, [
+				{
+					fieldLabel: '',
+					fieldName: 'test',
+					fieldType: 'hiddenField',
+				},
+			]);
+
+			expect(result[0]).toEqual({
+				fieldLabel: 'test',
+				fieldName: 'test',
+				fieldType: 'hiddenField',
+			});
+		});
+	});
 });

packages/nodes-base/nodes/Form/utils.ts

@@ -72,6 +72,28 @@ export function sanitizeHtml(text: string) {
 	});
 }
 
+export const prepareFormFields = (context: IWebhookFunctions, fields: FormFieldsParameter) => {
+	return fields.map((field) => {
+		if (field.fieldType === 'html') {
+			let { html } = field;
+
+			if (!html) return field;
+
+			for (const resolvable of getResolvables(html)) {
+				html = html.replace(resolvable, context.evaluateExpression(resolvable) as string);
+			}
+
+			field.html = sanitizeHtml(html as string);
+		}
+
+		if (field.fieldType === 'hiddenField') {
+			field.fieldLabel = field.fieldName as string;
+		}
+
+		return field;
+	});
+};
+
 export function sanitizeCustomCss(css: string | undefined): string | undefined {
 	if (!css) return undefined;
 
@@ -411,6 +433,8 @@ export function renderForm({
 		} catch (error) {}
 	}
 
+	formFields = prepareFormFields(context, formFields);
+
 	const data = prepareFormData({
 		formTitle,
 		formDescription,
@@ -476,17 +500,8 @@ export async function formWebhook(
 	}
 
 	const mode = context.getMode() === 'manual' ? 'test' : 'production';
-	const formFields = (context.getNodeParameter('formFields.values', []) as FormFieldsParameter).map(
-		(field) => {
-			if (field.fieldType === 'html') {
-				field.html = sanitizeHtml(field.html as string);
-			}
-			if (field.fieldType === 'hiddenField') {
-				field.fieldLabel = field.fieldName as string;
-			}
-			return field;
-		},
-	);
+	const formFields = context.getNodeParameter('formFields.values', []) as FormFieldsParameter;
+
 	const method = context.getRequestObject().method;
 
 	validateResponseModeConfiguration(context);