Re: [netmod] Module update rules: changing a type to a union

Martin Bjorklund <mbj@tail-f.com> Mon, 13 August 2018 10:08 UTC

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Date: Mon, 13 Aug 2018 12:08:16 +0200 (CEST)
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To: jason.sterne@nokia.com
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From: Martin Bjorklund <mbj@tail-f.com>
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Subject: Re: [netmod] Module update rules: changing a type to a union
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"Sterne, Jason (Nokia - CA/Ottawa)" <jason.sterne@nokia.com>; wrote:
> Hi all,
> 
> I'm uncertain about how to interpret the YANG module update rules when a type changes to a union.
> 
> Is the following change allowed?
> 
> From:
>   typedef my-type {
>     type enumeration {
>       enum "foo";
>     }
>   }
> To:
>   typedef my-type {
>     type union {
>       type enumeration {
>         enum "foo";
>       }
>       type uint32;
>     }
>   }
> 
> The general spirit of the rules is that expanding the value space is generally OK, but this case does seem to violate this paragraph of section 11:
> 
>    o  A "type" statement may be replaced with another "type" statement
>       that does not change the syntax or semantics of the type.  For
>       example, an inline type definition may be replaced with a typedef,
>       but an int8 type cannot be replaced by an int16, since the syntax
>       would change.

Right.  I think that changing from an enumeration to a union changes
the syntax of the type, so this would not be allowed.


/martin


> 
> 
> Does the addition of the union change the semantics of the type if that union encompasses the original type?
> 
> With XML encoding I can see how an "old" client could easily still communicate with a "new" server for this change. But I wonder about other possible encodings that might change when a type becomes a union that contains additional types.
> 
> Regards,
> Jason