Tracker http://joomlacode.org/gf/project/joomla/tracker/?action=TrackerItemEdit&tracker_item_id=31339

Actually if we did this and then added

    if (isset($table->newTags))
    {
        $newTags = $table->newTags;
    }

In tags.php at line 774 we could take out the $new->tags from the call and thus not have a change in api. Which would be great.

What I would say is let's add a property that indicates if a table supports tagging (because we don't have a field like asset_id or hits to check for). Then if that is true, set the newTags property.

So
/*

• @var Boolean indicating if tagging is supported */

$tagsSupport = true;

// If tagging is supported and the newTags property does not exists, set the default.
if ($this->tags && !property_exists($this, 'newTags'))
{
$this->newTags = array();
}

I think there is more overhead on checking if the tagging is supported than simply setting the $this->newTags = array();.
Adding an empty array property to the object isn't really that big of a deal.

No it makes more sense because it is more generally useful to have that information all the time (since tags is used for many other things) than it is to always have the information that you only need if you happen to be in a store context and not have any new tags. It's very useful for many many purposes (such as rendering and doing queries) to know if tags is supported especially as we try to make those things more and more generic.

See #1452