Good answer. If I may add.

You can't use Output or ByRef arguments on these functions, or let me rather say that I have not gotten it to work.

What you can do is return a collection type property, or you can pass in the context as a parameter to set properties on the context.
If you are wondering how to reference a context in a ruleset, add a property to you context of type %RegisteredObject and call it something like RefToSelf. Set the property to the OREF of the context once the context has been created.
Then in the rulefunction call, you pass in RefToSelf.

Hi,

My 2c on this, and maybe I am missing something or do not know how to use these VSCode extensions correctly.
The single source of truth principle can't really be applied when using these extensions, as BPLs, transformations, and rulesets should still be edited in the Management Portal or in Studio.

Because there is not a sync functionality, I have seen devs overwriting changes on BPLs, etc., when they import and compile from VSCode. You have to explicitly export it on the server explorer.

Please correct me if I'm mistaking.

Just to keep you informed.

I did a few tests. The more columns selected, the slower the output is, and quite significantly.