There's code using webidl2.js to parse IDL snippets and then applying partials/mixins in at least 3 different places:

• idlharness.js
• webref
• mdn-bcd-collector

None of them are entirely correct in the handling of [Exposed] and updating them individually is a nuisance.

How about a compile(ast), merge(ast), or simplify(ast) method that folds in partials and mixins as part of webidl2.js?