Using Drupal 8 Feeds with Xpath parser, can I concatenate two attribute values that appear in a single tag?
Well, I have a solution but it's not elegant. I used this query:
//theme/@name|//theme/@rank

and Imploded the resulting array to get theme1,rank1,theme2,rank2, etc,

then used a regex to replace every odd comma with a dash:
/(\w+)\W*,\W*(\w+)/
$1-$2

and then Exploded back to an array.

Would still like to know if there's a better alternative.