On Fri, Sep 30, 2016 at 9:01 AM, Balazs Lengyel <balazs.leng...@ericsson.com
> wrote:
> My biggest problem with deviations is that a number of things can not be
> deviated:
>
> - description
> - reference
>
>
This does seem quite useful.
I wonder why it got left out.
The way deviations work is rather counter-intuitive to those of us who think
of deviations as source code patches. Almost all deviations are source
code patches,
except type-stmt, and some default-stmt replacements.
It would be nice if a YANG tool could process all the deviations advertised
by the server
and produce a set of valid "deviated modules" which could then be fed to a
YANG compiler
that did not support deviations. This is non-trivial and not always
possible, because of the type-stmt
and possible import loops.
>
> Regards Balazs
>
>
Andy
> On 2016-09-30 00:22, Andy Bierman wrote:
>
> Hi,
>
> The deviation section has a lot of fluff text about how bad deviations are,
> but very little text on how to process the "deviate" statement correctly.
>
> The text is not clear if the statements altered in the target module
> are semantic patches or syntactic patches. Are the sub-statements
> of the deviate-stmt fully processed in the scope of the deviation module
> or in the scope of the target module? In this example, is the type-stmt
> resolved in A or dev-A?
>
> Similar issues for deviating a default for an identityref.
>
>
> module A {
> namespace "...";
> prefix a;
> // no imports!
>
> leaf foo {
> type string;
> }
>
> leaf bar {
> type string;
> }
>
> leaf baz {
> type string;
> }
> }
>
> module A-dev {
> ...
> import A { prefix a; }
> import C { prefix c; }
> import ietf-interfaces { prefix if; }
>
> // variant 1: inline leafref but module A does not import path module
> deviation /a:foo {
> deviate replace {
> type leafref {
> base /c:modules/c:module/c:name;
> }
> }
> }
>
>
> // variant 2: imported typedef but module A does not import it
> deviation /a:bar {
> deviate replace {
> type if:interface-ref;
> }
> }
>
>
> // variant 3: local typedef but module A cannot import it (circular
> imports)
> typedef mystring {
> type string { length "1..10"; }
> }
>
> deviation /a:baz {
> deviate replace {
> type mystring;
> }
> }
> }
>
>
> Andy
>
>
>
> _______________________________________________
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>
>
> --
> Balazs Lengyel Ericsson Hungary Ltd.
> Senior Specialist
> Mobile: +36-70-330-7909 email: balazs.leng...@ericsson.com
>
>
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