fix(channels): return channel messages instead of an always-empty list (#625)

CHANGELOG.md

@@ -11,6 +11,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - **Native WhatsApp polls** via `POST /api/sessions/:sessionId/messages/send-poll`: question, 2–12 options and an optional `allowMultipleAnswers` flag (default single choice), implemented on both engines (whatsapp-web.js `Poll`, Baileys `poll` content with `selectableCount` 1/0). The message history stores the poll question as the body so the log stays readable. Polls are a first-class `poll` message type end to end — both engines map incoming poll messages to it, so the websocket/webhook events, persisted rows, and dashboard all report `poll` consistently. Thanks @alejo117.
 
+### Fixed
+
+- **`GET /api/sessions/:sessionId/channels/:channelId/messages` always returned an empty array** on the whatsapp-web.js engine (#625). The adapter called `client.getChannelById()`, which does not exist in whatsapp-web.js 1.34.x, so every call threw and the error was swallowed into `[]`. Channel messages are now read from the subscribed `Channel` instance (via `getChannels()`), and an unknown/unsubscribed channel returns a `404` (`ChannelNotFoundError`) instead of a silent empty `200` — matching `GET /channels/:channelId`. Thanks @Header9968.
+
 ## [0.8.7] - 2026-07-03
 
 ### Added

src/common/errors/channel-not-found.error.ts

@@ -0,0 +1,16 @@
+import { NotFoundException } from '@nestjs/common';
+
+/**
+ * Thrown by the engine layer when a channel referenced by id isn't among the session's subscribed
+ * channels (a wrong/typo'd id, or a channel not yet synced into the local collection).
+ *
+ * Extends NestJS `NotFoundException` so it maps to **HTTP 404** through the built-in exception
+ * handler — i.e. it does NOT depend on a custom global filter being registered, and it survives the
+ * `channel.service` passthrough — instead of surfacing as a generic 500 Internal Server Error.
+ * Mirrors {@link MessageNotFoundError}.
+ */
+export class ChannelNotFoundError extends NotFoundException {
+  constructor(channelId: string) {
+    super(`Channel ${channelId} not found`);
+  }
+}

src/engine/adapters/whatsapp-web-js.adapter.spec.ts

@@ -16,6 +16,7 @@ import * as qrcode from 'qrcode';
 import { UnprocessableEntityException } from '@nestjs/common';
 import { EngineNotReadyError } from '../../common/errors/engine-not-ready.error';
 import { EngineNotSupportedError } from '../../common/errors/engine-not-supported.error';
+import { ChannelNotFoundError } from '../../common/errors/channel-not-found.error';
 import { EngineStatus } from '../interfaces/whatsapp-engine.interface';
 import { SsrfBlockedError } from '../../common/security/ssrf-guard';
 import { fetch as undiciFetch } from 'undici';
@@ -365,6 +366,61 @@ describe('WhatsAppWebJsAdapter.forwardMessage (returns the real sent id, not a s
   });
 });
 
+describe('WhatsAppWebJsAdapter channels (#625 — wwebjs Client has no getChannelById)', () => {
+  const CHANNEL = '120363401234567890@newsletter';
+
+  const readyAdapter = (client: unknown): WhatsAppWebJsAdapter => {
+    const adapter = new WhatsAppWebJsAdapter({ sessionId: 's', sessionDataPath: './data/sessions', puppeteer: {} });
+    (adapter as unknown as { status: EngineStatus }).status = EngineStatus.READY;
+    (adapter as unknown as { client: unknown }).client = client;
+    return adapter;
+  };
+
+  it('getChannelMessages fetches via the subscribed Channel (getChannels), not the non-existent getChannelById', async () => {
+    const fetchMessages = jest
+      .fn()
+      .mockResolvedValue([{ id: { _serialized: 'M1' }, body: 'hello', timestamp: 1700000000, hasMedia: false }]);
+    const getChannels = jest.fn().mockResolvedValue([{ id: { _serialized: CHANNEL }, name: 'News', fetchMessages }]);
+
+    const result = await readyAdapter({ getChannels }).getChannelMessages(CHANNEL, 10);
+
+    expect(getChannels).toHaveBeenCalled();
+    expect(fetchMessages).toHaveBeenCalledWith({ limit: 10 });
+    expect(result).toEqual([{ id: 'M1', body: 'hello', timestamp: 1700000000, hasMedia: false, mediaUrl: undefined }]);
+  });
+
+  it('getChannelMessages surfaces a not-found channel as ChannelNotFoundError (→ 404), not a silent []', async () => {
+    const getChannels = jest
+      .fn()
+      .mockResolvedValue([{ id: { _serialized: 'other@newsletter' }, fetchMessages: jest.fn() }]);
+    // Typed NotFoundException subclass so it maps to 404, not a plain Error → generic 500.
+    await expect(readyAdapter({ getChannels }).getChannelMessages(CHANNEL)).rejects.toBeInstanceOf(
+      ChannelNotFoundError,
+    );
+  });
+
+  it('getChannelMessages returns [] for a channel with no messages (empty is not an error)', async () => {
+    const fetchMessages = jest.fn().mockResolvedValue([]);
+    const getChannels = jest.fn().mockResolvedValue([{ id: { _serialized: CHANNEL }, name: 'News', fetchMessages }]);
+    await expect(readyAdapter({ getChannels }).getChannelMessages(CHANNEL)).resolves.toEqual([]);
+  });
+
+  it('getChannelById resolves from the subscribed-channel list (no getChannelById call)', async () => {
+    const getChannels = jest
+      .fn()
+      .mockResolvedValue([
+        { id: { _serialized: CHANNEL }, name: 'News', description: 'desc', subscriberCount: 5, verified: true },
+      ]);
+    const ch = await readyAdapter({ getChannels }).getChannelById(CHANNEL);
+    expect(ch).toMatchObject({ id: CHANNEL, name: 'News', description: 'desc', subscriberCount: 5, verified: true });
+  });
+
+  it('getChannelById returns null for a channel not in the subscribed list (service maps null → 404)', async () => {
+    const getChannels = jest.fn().mockResolvedValue([{ id: { _serialized: 'other@newsletter' }, name: 'Other' }]);
+    await expect(readyAdapter({ getChannels }).getChannelById(CHANNEL)).resolves.toBeNull();
+  });
+});
+
 describe('WhatsAppWebJsAdapter channel-JID guard (#554 — wwebjs Channel lacks Chat methods)', () => {
   const NEWSLETTER = '120363401234567890@newsletter';
   const USER = '628111@c.us';

src/engine/adapters/whatsapp-web-js.adapter.ts

@@ -42,6 +42,7 @@ import { createLogger } from '../../common/services/logger.service';
 import { EngineNotReadyError } from '../../common/errors/engine-not-ready.error';
 import { EngineNotSupportedError } from '../../common/errors/engine-not-supported.error';
 import { MessageNotFoundError } from '../../common/errors/message-not-found.error';
+import { ChannelNotFoundError } from '../../common/errors/channel-not-found.error';
 import { loadRemoteMediaBuffer } from '../../common/media/load-remote-media';
 import {
   GroupChat,
@@ -1463,23 +1464,9 @@ export class WhatsAppWebJsAdapter extends EventEmitter implements IWhatsAppEngin
 
   async getChannelById(channelId: string): Promise<Channel | null> {
     this.ensureReady();
-    try {
-      const ch = await (this.client as unknown as BusinessClient).getChannelById(channelId);
-      if (!ch) {
-        return null;
-      }
-      return {
-        id: String(typeof ch.id === 'object' ? ch.id._serialized : ch.id),
-        name: String(ch.name || ''),
-        description: ch.description ? String(ch.description) : undefined,
-        inviteCode: ch.inviteCode ? String(ch.inviteCode) : undefined,
-        subscriberCount: ch.subscriberCount ? Number(ch.subscriberCount) : undefined,
-        verified: ch.verified ? Boolean(ch.verified) : undefined,
-      };
-    } catch (error) {
-      this.logger.warn(`Failed to get channel: ${channelId}`, String(error));
-      return null;
-    }
+    // wwebjs 1.34.x exposes no client.getChannelById; resolve from the subscribed-channel list (#625).
+    const channels = await this.getSubscribedChannels();
+    return channels.find(c => c.id === channelId) ?? null;
   }
 
   async subscribeToChannel(inviteCode: string): Promise<Channel> {
@@ -1501,26 +1488,24 @@ export class WhatsAppWebJsAdapter extends EventEmitter implements IWhatsAppEngin
 
   async getChannelMessages(channelId: string, limit: number = 50): Promise<ChannelMessage[]> {
     this.ensureReady();
-    try {
-      const ch = await (this.client as unknown as BusinessClient).getChannelById(channelId);
-      if (!ch) {
-        throw new Error(`Channel ${channelId} not found`);
-      }
-      const messages = await ch.fetchMessages({ limit });
-      if (!messages) {
-        return [];
-      }
-      return messages.map(msg => ({
-        id: String(typeof msg.id === 'object' ? msg.id._serialized : msg.id),
-        body: String(msg.body || ''),
-        timestamp: Number(msg.timestamp),
-        hasMedia: Boolean(msg.hasMedia),
-        mediaUrl: msg.mediaUrl ? String(msg.mediaUrl) : undefined,
-      }));
-    } catch (error) {
-      this.logger.error(`Failed to get channel messages: ${String(error)}`);
-      return [];
-    }
+    // wwebjs 1.34.x has no client.getChannelById (calling it threw and the error was swallowed into an
+    // empty list, #625). The subscribed Channel instances returned by getChannels() carry fetchMessages(),
+    // so resolve the channel from that list and read its messages. A missing channel surfaces as a
+    // ChannelNotFoundError (→ 404, like getChannelById) so callers can tell "no messages" apart from
+    // "wrong/unsubscribed channel" instead of getting a silent [].
+    const channels = await (this.client as unknown as BusinessClient).getChannels();
+    const channel = channels?.find(c => (typeof c.id === 'object' ? c.id._serialized : c.id) === channelId);
+    if (!channel) {
+      throw new ChannelNotFoundError(channelId);
+    }
+    const messages = await channel.fetchMessages({ limit });
+    return (messages ?? []).map(msg => ({
+      id: String(typeof msg.id === 'object' ? msg.id._serialized : msg.id),
+      body: String(msg.body || ''),
+      timestamp: Number(msg.timestamp),
+      hasMedia: Boolean(msg.hasMedia),
+      mediaUrl: msg.mediaUrl ? String(msg.mediaUrl) : undefined,
+    }));
   }
 
   // ========== Gap Quick Wins Implementation ==========

src/engine/types/whatsapp-web-js.types.ts

@@ -72,12 +72,11 @@ export interface MessageWithReactions extends Omit<Message, 'hasReaction' | 'get
  */
 export interface BusinessClient extends Omit<
   Client,
-  'subscribeToChannel' | 'unsubscribeFromChannel' | 'getLabels' | 'getLabelById' | 'getChannels' | 'getChannelById'
+  'subscribeToChannel' | 'unsubscribeFromChannel' | 'getLabels' | 'getLabelById' | 'getChannels'
 > {
   getLabels(): Promise<Array<{ id: string; name: string; hexColor: string }>>;
   getLabelById(id: string): Promise<{ id: string; name: string; hexColor: string } | null>;
   getChannels(): Promise<WwjsChannelData[]>;
-  getChannelById(id: string): Promise<WwjsChannelData | null>;
   subscribeToChannel(inviteCode: string): Promise<WwjsChannelData>;
   unsubscribeFromChannel(id: string): Promise<void>;
 }