mm_emfield calls node_save() during node_delete()

When the user deletes a node, mm_emfield_media_mover() gets called with $op='delete', which then calls mm_emfield_node_file_delete(), which then calls node_save().

function mm_emfield_media_mover($op, $action = null, $configuration = null, &$file = array(), $job = null, $nid = null) {
  if (module_exists('emfield')) {
    switch ($op) {
      ...
      case 'delete':
        if ($action == MM_EMFIELD_STORE || $action == MM_EMFIELD_COMPLETE) {
          mm_emfield_node_file_delete($configuration, $file);
        }
        break;
    }
  }

As a result, node_save() gets called while node_delete() is in the midst of executing. This causes a bunch of problems when a node is deleted, including:

1. The emfield rows in content_field_myemfield, corresponding to the deleted node's harvested files, are not deleted. (The columns are instead set to NULL, because node_save() causes hook_nodeapi to get called with $op='update'.) See http://drupal.org/node/1497418
2. Similarly, the rows in the content_field_myfilefield database table, corresponding to the deleted node's harvested files, are not deleted.
3. Emfield outputs error message "unserialize() expects parameter 1 to be string". See http://drupal.org/node/1308856.
4. Multiple calls to hook_nodeapi with $op='update', when user deletes node.

I modified media_mover_api.module so that mm_emfield_node_file_delete() is no longer called when a node is deleted. As a result, node_save() is no longer called in the midst of executing node_delete(), and all of the problems listed above went away.

The basic idea was to add an $op to hook_media_mover(), to distinguish between "user has deleted a node" ($op='node_delete') and "user has deleted a file" ($op='delete'). mm_emfield's implementation of hook_media_mover is then able to distinguish these two cases, and call mm_emfield_node_file_delete() only when the user has deleted a file, but not when the user has deleted a node. In this way, node_save() is no longer called in the midst of executing node_delete().

Because this approach distinguishes 'node_delete' from 'delete', it may be necessary to modify the implementation of hook_media_mover() in some other modules. For example, I found it was necessary to add a case statement for $op='node_delete' to mm_s3's implementation of hook_media_mover(), so that mm_s3_delete_file() would get called both when the user deleted a node and when the user deleted a file.

Here are the detailed code changes:

function media_mover_api_node_files_delete()
In the call to media_mover_api_file_delete_call(), I pass $op='node_delete' as a second parameter, to indicate that the user had deleted a node.

function media_mover_api_node_files_delete($node) {
     ...
      if ($configuration->settings->mma_node_item_delete) {
        foreach ($mm_files as $mm_file) {
           // media_mover_api_file_delete_call($mm_file); // original code
           media_mover_api_file_delete_call($mm_file, 'node_delete'); // <--- HERE.  added second parameter
        }
      ...
}

function media_mover_api_file_delete_call()
The function accepts a second parameter, which by default is 'delete', and passes this parameter to _media_mover_api_module_invoke().

function media_mover_api_file_delete_call($file, $op='delete') {
  foreach (media_mover_api_verbs() as $verb) {
    // _media_mover_api_module_invoke($configuration->{$verb}->module, 'media_mover', 'delete', $configuration->{$verb}->action, $configuration->{$verb}->configuration, $file, $configuration); // original code
  _media_mover_api_module_invoke($configuration->{$verb}->module, 'media_mover', $op, $configuration->{$verb}->action, $configuration->{$verb}->configuration, $file, $configuration); // <--- HERE.  replaced 'delete' with $op

  }

With the changes above, mm_emfield_media_mover() no longer calls mm_emfield_node_file_delete() when a node has been deleted.

function mm_s3_media_mover()
I modified mm_s3's implementation of hook_media_mover to support these changes.

function mm_s3_media_mover($op, $action_id = null, $configuration = array(), &$file = array()) {
   switch ($op) {
     case 'node_delete':  // <--- HERE.  Added this line, so mm_s3_delete_file() gets called when node is deleted
     case 'delete':
        mm_s3_delete_file($file, $configuration);
     break;
   }
}