Import from feed using a selector only if it has a given XML attribute

Question

I'm working on an import from an RSS feed that includes two types of XML <category> elements:

• Subject Areas, e.g. <category>Economics | Social and Behavioral Sciences</category>
• Keywords, e.g. <category domain="keywords">immigration, emigration, immigrants, international migration, poverty, immigration enforcement, asylum policy</category>

I want to import the Keywords as their own taxonomy field. I can write the YAML as follows, but it predictably imports both Keywords and Subject Areas:

source:
  fields:
    -
      name: keywords
      label: Keywords
      selector: 'category'
process:
  field_keywords:
    -
      plugin: explode
      delimiter: ', '
      source: keywords
    -
      plugin: entity_generate

How do I adjust the selector so it only pulls from the <category> element that includes the domain="keywords" attribute?

Answer 1

I figured this out with the help of an XPATH cheatsheet that shows how selectors I might have written to target HTML would transfer to XPATH values.

To only pull <category domain="keywords"> items, I can use category[@domain="keywords"] as my selector. The other set of <category> items don't have a domain attribute, so I pulled them separately using the selector category[not(@domain)].