Re: [Cbor] CDDL 2.0 import and paths

[Carsten Bormann <[e-mail]>]

Christian made a great list of requirements in his email dated 2023-01-25.

cddlc 0.1.2 now implements a tiny bit of that.

   gem update cddlc

(or `gem install cddlc` if you didn’t have that yet.  Requires Ruby ≥ 3.0.)

I didn’t really want to nail pathnames or partial URIs into the CDDL files, so I added a simple CDDL_INCLUDE_PATH as an environment variable.  This is the usual colon-separated list, with a special feature: an empty element points to cddlc’s own collection, which contains 20 fragments of extracted CDDL from published RFCs(**).  If you are missing anything, please tell me.  

I did not implement Web paths (which is interesting because of the colon), some more thinking required.  (There are no useful collections of extracted CDDL on the Web yet that I am aware of, and extractors are another work item.)

The default CDDL_INCLUDE_PATH is  .:  — so you get files out of the current directory and, if not found there, cddlc’s collection.

Based on this, I implemented two directives for now:

;# include rfc9052
;;; include all the rules from rfc9052.cddl as well as the ones imported/included there, no questions asked

and

;# import rfc9052
;;; include only those rules from rfc9052.cddl that actually are undefined references in the current CDDL file, treating rfc9052 as a “library”.

I plan to add something like

;# import rfc9052 as COSE

which would rename the names in the imported rules to start with COSE(*).
(This is of course interesting because of other imported names, as well as prelude names…)

Please have a look.  My favorite command to play with this is

cddlc -2 -tcddl mytestfile.cddl | cddl - gp 10

I’ll update the cddl2 plan document as well as the implementation when I have some feedback.

This is not yet the Pareto 80 %, but already goes surprisingly far!

Grüße, Carsten

(*) I’m not yet sure whether the auto-import mechanism should add glue rules automatically, so you don’t have to call your referencing names COSE.COSE_Encrypt0 while still getting overly generic names such as `label` or `values` prefixed as `COSE.label` and `COSE.values`.  This could be limited to specific names listed in a “import … from” part of the directive.  I need to see more examples to make a useful suggestion.

(**) I also need to reserve an afternoon for submitting all the errata reports for the extracted CDDL.  From a missing closing parenthesis via word wrapping out of a comment to using # as the comment character.  Ouch.