fix(Zulip Node): Normalize multiOptions recipients when expression returns a string (#31492)

Co-authored-by: Dawid Myslak <dawid.myslak@gmail.com>

packages/nodes-base/nodes/Zulip/GenericFunctions.ts

@@ -56,6 +56,28 @@ export async function zulipApiRequest(
 	}
 }
 
+// A multiOptions parameter normally resolves to an array. When its value comes
+// from an expression that is wrapped in surrounding text/whitespace, n8n
+// switches to string interpolation and the array is coerced to a comma-joined
+// string. Accept both shapes so the node degrades gracefully instead of
+// throwing a low-level "join is not a function" TypeError.
+export function toMultiOptionsCsv(value: unknown): string {
+	if (Array.isArray(value)) {
+		return value
+			.map((entry) => String(entry).trim())
+			.filter((entry) => entry.length > 0)
+			.join(',');
+	}
+	if (typeof value === 'string') {
+		return value
+			.split(',')
+			.map((entry) => entry.trim())
+			.filter((entry) => entry.length > 0)
+			.join(',');
+	}
+	return '';
+}
+
 export function validateJSON(json: string | undefined): any {
 	let result;
 	try {

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

@@ -10,7 +10,7 @@ import type {
 } from 'n8n-workflow';
 import { NodeConnectionTypes, NodeOperationError } from 'n8n-workflow';
 
-import { validateJSON, zulipApiRequest } from './GenericFunctions';
+import { toMultiOptionsCsv, validateJSON, zulipApiRequest } from './GenericFunctions';
 import { messageFields, messageOperations } from './MessageDescription';
 import type { IMessage } from './MessageInterface';
 import { streamFields, streamOperations } from './StreamDescription';
@@ -138,7 +138,7 @@ export class Zulip implements INodeType {
 				if (resource === 'message') {
 					//https://zulipchat.com/api/send-message
 					if (operation === 'sendPrivate') {
-						const to = (this.getNodeParameter('to', i) as string[]).join(',');
+						const to = toMultiOptionsCsv(this.getNodeParameter('to', i));
 						const content = this.getNodeParameter('content', i) as string;
 						const body: IMessage = {
 							type: 'private',

packages/nodes-base/nodes/Zulip/test/GenericFunctions.test.ts

@@ -0,0 +1,46 @@
+import { toMultiOptionsCsv } from '../GenericFunctions';
+
+describe('Zulip > GenericFunctions', () => {
+	describe('toMultiOptionsCsv', () => {
+		it('joins array values', () => {
+			expect(toMultiOptionsCsv(['user1@example.com', 'user2@example.com'])).toBe(
+				'user1@example.com,user2@example.com',
+			);
+		});
+
+		it('trims entries inside an array (interpolated array elements)', () => {
+			expect(toMultiOptionsCsv(['user1@example.com ', ' user2@example.com'])).toBe(
+				'user1@example.com,user2@example.com',
+			);
+		});
+
+		it('coerces non-string array entries via String()', () => {
+			expect(toMultiOptionsCsv([1, 2, 3])).toBe('1,2,3');
+		});
+
+		it('accepts a comma-joined string (the whitespace-expression coercion case)', () => {
+			expect(toMultiOptionsCsv('user1@example.com,user2@example.com ')).toBe(
+				'user1@example.com,user2@example.com',
+			);
+		});
+
+		it('trims whitespace around each entry in a comma-string', () => {
+			expect(toMultiOptionsCsv(' user1@example.com , user2@example.com ')).toBe(
+				'user1@example.com,user2@example.com',
+			);
+		});
+
+		it('drops empty entries', () => {
+			expect(toMultiOptionsCsv(['user1@example.com', '', '  ', 'user2@example.com'])).toBe(
+				'user1@example.com,user2@example.com',
+			);
+		});
+
+		it('returns an empty string for undefined/null/empty values', () => {
+			expect(toMultiOptionsCsv(undefined)).toBe('');
+			expect(toMultiOptionsCsv(null)).toBe('');
+			expect(toMultiOptionsCsv('')).toBe('');
+			expect(toMultiOptionsCsv([])).toBe('');
+		});
+	});
+});