src/polling: Fix the Offset Infinite Loop bug

References:

  * Issue #36: #36
    * answer/solution: #36 (comment)

doc/api.md

@@ -122,6 +122,7 @@ Emits `message` when a message arrives.
 | [options.request] | <code>Object</code> |  | Options which will be added for all requests to telegram api.  See https://github.com/request/request#requestoptions-callback for more information. |
 | [options.baseApiUrl] | <code>String</code> | <code>https://api.telegram.org</code> | API Base URl; useful for proxying and testing |
 | [options.filepath] | <code>Boolean</code> | <code>true</code> | Allow passing file-paths as arguments when sending files,  such as photos using `TelegramBot#sendPhoto()`. See [usage information][usage-sending-files-performance]  for more information on this option and its consequences. |
+| [options.badRejection] | <code>Boolean</code> | <code>false</code> | Set to `true`  **if and only if** the Node.js version you're using terminates the  process on unhandled rejections. This option is only for  *forward-compatibility purposes*. |
 
 <a name="TelegramBot+on"></a>
 

src/telegram.js

@@ -174,6 +174,10 @@ class TelegramBot extends EventEmitter {
    * @param {Boolean} [options.filepath=true] Allow passing file-paths as arguments when sending files,
    *  such as photos using `TelegramBot#sendPhoto()`. See [usage information][usage-sending-files-performance]
    *  for more information on this option and its consequences.
+   * @param {Boolean} [options.badRejection=false] Set to `true`
+   *  **if and only if** the Node.js version you're using terminates the
+   *  process on unhandled rejections. This option is only for
+   *  *forward-compatibility purposes*.
    * @see https://core.telegram.org/bots/api
    */
   constructor(token, options = {}) {
@@ -184,6 +188,7 @@ class TelegramBot extends EventEmitter {
     this.options.webHook = (typeof options.webHook === 'undefined') ? false : options.webHook;
     this.options.baseApiUrl = options.baseApiUrl || 'https://api.telegram.org';
     this.options.filepath = (typeof options.filepath === 'undefined') ? true : options.filepath;
+    this.options.badRejection = (typeof options.badRejection === 'undefined') ? false : options.badRejection;
     this._textRegexpCallbacks = [];
     this._replyListenerId = 0;
     this._replyListeners = [];

src/telegramPolling.js

@@ -79,6 +79,18 @@ class TelegramBotPolling {
     return !!this._lastRequest;
   }
 
+  /**
+   * Handle error thrown during polling.
+   * @private
+   * @param  {Error} error
+   */
+  _error(error) {
+    if (!this.bot.listeners('polling_error').length) {
+      return console.error('error: [polling_error] %j', err); // eslint-disable-line no-console
+    }
+    return this.bot.emit('polling_error', error);
+  }
+
   /**
    * Invokes polling (with recursion!)
    * @return {Promise} promise of the current request
@@ -99,12 +111,25 @@ class TelegramBotPolling {
       })
       .catch(err => {
         debug('polling error: %s', err.message);
-        if (this.bot.listeners('polling_error').length) {
-          this.bot.emit('polling_error', err);
-        } else {
-          console.error('error: [polling_error] %j', err); // eslint-disable-line no-console
+        /**
+         * We need to mark the already-processed items
+         * to avoid fetching them again once the application
+         * is restarted, or moves to next polling interval
+         * (in cases where unhandled rejections do not terminate
+         * the process).
+         * See https://github.com/yagop/node-telegram-bot-api/issues/36#issuecomment-268532067
+         */
+        if (!this.bot.options.badRejection) {
+          return this._error(err);
         }
-        return null;
+        const opts = {
+          offset: this.options.params.offset,
+          limit: 1,
+          timeout: 0,
+        };
+        return this.bot.getUpdates(opts).then(() => {
+          return this._error(err);
+        });
       })
       .finally(() => {
         if (this._abort) {