A callback is implemented against a contract given by a behaviour, which dictates names and arities, so you now all you need…
Please check if the :decorator package suites your needs or if you can take some insights from it.
Maybe you can also pull some use from the @on_definition module attribute.
At the moment, I really can’t tell you anything more, since I simply do ot understand what you want to achieve… You say, you want to decorate all foo, but then you say you do not know what you want to decorate, and then again you say thats a callback, so you have a contract… I’m confused about your plans…
