Enable modules to hook into existing parsers

How's this? (see patch)

Here's what an implementation of the hooks might look like:

/**
 * Implementation of parser_simplepie_feed().
 * @param $feed The feed's url
 * @param $parser The instance of SimplePie
 * @param $parsed_source A reference to the object that will be returned from parser_simplepie_feedapi_parse()
 */
function motogpod_parser_simplepie_feed($feed, $parser, &$parsed_source) {
  drupal_set_message("motogpod_parser_simplepie_feed($parsed_source->title)");
  $parsed_source->title = 'FOO: ' . $parsed_source->title;
}

/**
 * Implementation of parser_simplepie_item().
 * @param $simplepie_item
 * @param $curr_item
 */
function motogpod_parser_simplepie_item($simplepie_item, &$curr_item) {
  drupal_set_message("motogpod_parser_simplepie_item($curr_item->title)");
  $curr_item->title = 'BAR: ' . $curr_item->title;
}

Updated title, category and status.

No, the parsers are independent.

The reason I had to patch simplepie was because simplepie doesn't keep track of any fields in the feed or item that it doesn't know about (eg: enclosures! and some iTunes specific stuff). This patch allows custom modules to save whatever they want, and use it later when creating the nodes.

FWIW, I also patched feedapi_item to allow modules to mess with the node being created, using the data saved in the parser. Both these changes were required so that I could perform a reasonably simple task: consume a podcast RSS feed, and create audio nodes from it:

- I used the first parser hook to set_time_limit(0); (since downloading the MP3s takes quite a while) IIRC, I also saved a couple of attributes, so I could use them later when creating nodes.

- I used the second parser hook to add the enclosure information from the $simplepie_item into the $feed_item (so we can download it in the item processor)

- I used the extra hook mentioned above to customize $node after feedapi_item had created a default. In my case, I created an audio node using the audio API, then copied the pertinent fields from $mynode into $node.

I think if I was doing it again now, I'd also pass $feed into the item processor, which may reduce the need for the first hook.

The patch in this issue still applies correctly to DRUPAL-5 feedapi (with an offset). Or are you talking about the patch to feedapi_item? It's trivial, attached.

PS: I'm not especially attached to the hook names, or even the exact parameters, I just wanted to open a discussion about the ability to extend existing parsers/processors without duplicating them entirely.

FWIW, the podcast example I talked about above, used the roughly the following hooks in my module:

(simplepie item hook) This particular bit of code saves the enclosure from the item into the feeditem options, and actually fiddles with the title/description (by pulling the first line of the RSS item description into the title, rather than using the title that was in the <item>.

/**
 * Implementation of parser_simplepie_item().
 * @param $simplepie_item
 * @param $curr_item
 */
function motogpod_parser_simplepie_item($simplepie_item, &$feed_item) {
  // save the enclosure from the simplepie item into the feed options
  $feed_item->options->enclosure = $simplepie_item->get_enclosure();

  // fixup $node from RSS feed
  if (preg_match('#^(Episode[^\r\n]*)#', $feed_item->description, $matches)) {
    $feed_item->title = $matches[1];
    $feed_item->description = preg_replace('#^Episode[^\r\n]*#', '', $feed_item->description);
    $feed_item->options->teaser = $feed_item->description;
  }
}

(feedapi_item save hook) This bit of code uses the information saved above to download the MP3 enclosure, and create an audio node using Audio API. It then copies the information from the node it just created into $node, so when the caller calls node_save, it's really an update, not a create-new. Some error checking/etc removed for clarity.

function motogpod_feedapi_item_savehook(&$feed_item, &$node) {
  // only download the MP3 on a create, not an update
  if (!isset($feed_item->nid)) {

    // determine the URL of the mp3
    $mp3url = $feed_item->options->enclosure->link;

    // removed: fetch the mp3, save as $filename

    // create the new node using audio_api_insert()
    $new_node = audio_api_insert($filename, $feed_item->title);

    // copy information about the audio node into $node
    $node->nid = $new_node->nid;
    $node->audio_tags = $new_node->audio_tags;
    $node->audio_file = $new_node->audio_file;
    $node->audio_fileinfo = $new_node->audio_fileinfo;
  }

  // make other updates to the node
  $vocabs = taxonomy_get_vocabularies('audio');
  if ($vocabs) {
    $vocab = array_shift($vocabs);
    $node->taxonomy['tags'][$vocab->vid] = implode(',', $feed_item->options->enclosure->keywords);
  }
}

To be honest, I haven't updated this client to newer versions of FeedAPI, because I did their site before Aron established an upgrade path :)