Will this work with episodes by date?

Updated the commit to handle episodes by date.

Also, will this support other media types? Plex has music, movies etc libraries...

These changes are exclusive to entries determined to be Plex episodes.

As for movies, the only fields used by the movies metainfo plugins are title, imdb_id, and tmdb_id. Plex already provides the title. In most cases the title is sufficient to obtain the correct metainfo (although there is certainly the possibility of error).

Plex can provide the imdb_id for movies and the tvdb_id for TV shows by parsing urls that look like com.plexapp.agents.imdb://tt0338751?lang=en or com.plexapp.agents.thetvdb://248742/1/1?lang=en. But at that point we are just replacing Flexget lookup with Plex lookup. This seems like a poor decision because we lose control over the metainfo lookup logic for Plex entries. However I would be more than willing to add that as well if you think it would be a desired modification.

For other media (music, photos, and home videos), there aren't any metainfo plugins for these types of content, so there isn't any work to be done in this PR.

I got no issues with relying on metainfo retrieved via Plex or any other input source for that matter. The rare situation that the metadata is incorrect in the source does not match up to the advantage of adding metadata without needing additional lookup.

I was wondering if you added a check that knows if it should populate movie or series fields based on content type or library type or whatever

Okay, I'll add the metainfo id parsing to this PR.

That check already existed in this plugin (see the variable viewgroup). That info is determined in the XML returned by Plex. I'm using that to determine which fields to populate.

Currently, Flexget makes a single request to Plex and receives an XML response containing of list with limited info about the requested items in Plex. This limited info does not include the fields necessary to populate the imdb_id or tvdb_id. In order to populate these fields, Flexget would have to make an additional request for each entry listed in the original response. While this is certainly possible, it is outside the scope of this commit.

As I mentioned earlier, the info returned by Plex is almost always sufficient to retrieve movie metainfo using other plugins. This PR was motivated by the desire the ensure that the Plex plugin provides enough info for other metainfo plugins to retrieve info about series episodes.

Fair enough, thanks for this!