Subject: Re: [PATCH net-next v1 02/12] tools/net/ynl: Support sub-messages in nested attribute spaces

From: Jakub Kicinski <[email-masked]>
Date: Mon, 29 Jan 2024 17:32:59 -0800

On Sun, 28 Jan 2024 19:36:29 +0000 Donald Hunter wrote:
> > from collections import ChainMap
> >
> > class LevelChainMap(ChainMap):
> >     def __getitem__(self, key):
> >         for mapping in self.maps:
> >             try:
> >                 return mapping[key], self.maps[::-1].index(mapping)
> >             except KeyError:
> >                 pass
> >         return self.__missing__(key)
> >
> >     def get(self, key, default=None, level=None):
> >         val, lvl = self[key] if key in self else (default, None)
> >         if level:
> >             if lvl != level:
> >                 raise Exception("Level mismatch")
> >         return val, lvl
> >
> > # example usage
> > c = LevelChainMap({'a':1}, {'inner':{'a':1}}, {'outer': {'inner':{'a':1}}})
> > print(c.get('a', level=2))
> > print(c.get('a', level=1)) #raise err
> >
> > This will leave the spec as it is and will require small changes.
> >
> > What do you think?  
> 
> The more I think about it, the more I agree that using path-like syntax
> in the selector is overkill. It makes sense to resolve the selector
> level from the spec and then directly access the mappings from the
> correct scope level.

Plus if we resolve from the spec that's easily reusable in C / C++ 
code gen :)