Add file limit support.

src/FTPBatch.php

@@ -27,6 +27,7 @@ class FTPBatch implements BatchInterface {
     $file_list = $client->list($params['source_path']);
 
     $total = count($file_list);
+    $file_limit = $params['file_limit'] ?? 0;
     $files_to_process = [];
     $i = 0;
     foreach ($file_list as $file) {
@@ -43,6 +44,10 @@ class FTPBatch implements BatchInterface {
         ]);
         $files_to_process = [];
       }
+
+      if ($file_limit && $i >= $file_limit) {
+        break;
+      }
     }
 
     batch_set($batchBuilder->toArray());

src/Form/FTPBatchForm.php

@@ -86,13 +86,17 @@ class FTPBatchForm extends FormBase {
     $settings = $operation->getPluginSettings();
 
     $form['actions']['#type'] = 'actions';
-    $form['descriptions'] = [
+    $form['description'] = [
       '#markup' => $this->t('Connect to FTP server <b>%host</b> and transfer files from <b>%source</b> to <b>%destination</b>', [
         '%host' => $settings['hostname'],
         '%source' => $settings['source_path'],
         '%destination' => $settings['destination_path'],
       ]),
     ];
+    if ($settings['file_limit']) {
+      $form['description']['#markup'] .= '<br>';
+      $form['description']['#markup'] .= $this->t('<b>Transfer is limited to %limit of files.</b>', ['%limit' => $settings['file_limit']]);
+    }
     $form['actions']['submit'] = [
       '#type' => 'submit',
       '#value' => $this->t('Transfer'),

src/Plugin/file_sync/FTPDirectorySync.php

@@ -160,6 +160,12 @@ class FTPDirectorySync extends OperationPluginBase {
         '#description' => $this->t('Number of files to transfer per batch.'),
         '#default_value' => $settings['batch_size'] ?? 10,
       ];
+      $form['file_limit'] = [
+        '#type' => 'number',
+        '#title' => $this->t('Transfter file limit'),
+        '#description' => $this->t('Limit the number of files to be transfered. After exceeding the limit the operation will stop. <br>This is only useful for testing purposes. <strong>Defaults to "0" which means all files will be downloaded</strong>.'),
+        '#default_value' => $settings['file_limit'] ?? 0,
+      ];
       $form['batch'] = [
         '#type' => 'link',
         '#title' => $this->t('Transfer FTP files'),