Hi William,
I think that what yanglint is doing here is sane, i.e. I think that its
interpretation/split between imported vs implemented modules is
supported by the YANG RFC.
However, for validation purposes it seems that it would be useful if
yanglint had an option to assume that all imported modules are
implicitly implemented without requiring them to be explicitly specified.
Thanks,
Rob
On 06/03/2017 16:44, William Lupton wrote:
All,
This message arose from a yang-multic...@ietf.org
<mailto:yang-multic...@ietf.org> “draft-ietf-pim-igmp-mld-yang-02.txt:
YANG compilation isuse” (sic) thread
<https://www.ietf.org/mail-archive/web/yang-multicast/current/threads.html#00232> initiated
by Benoit.
I thought it would be useful for NETMOD to see the part of the
discussion that relates to implemented versus imported YANG modules.
1. Benoit Claise reported this warning:
* warn: Schema node "ietf-ip:ipv4" not found
(/ietf-interfaces:interfaces/ietf-interfaces:interface[ietf-interfaces:name
= current()]/ietf-ip:ipv4)
2. Radek Krejčí replied:
* These warnings are printed because in yanglint, until
explicitly stated, the imported modules (such as
ietf-interfaces and ietf-ip), are supposed to be only
imported, not implemented. The data nodes in imported schemas
are not available, which is the reason of these warnings.
3. William Lupton (that’s me!) asked / commented:
* Why are the complaints only about ip:ipv4 (etc) and not about
if:interfaces (etc), which are also referenced in the must
statements?
* This makes it hard for an automated tool (such as Benoit’s)
because it needs to know which other YANG files to process in
addition to the “file of interest”.
4. Radek Krejčí replied:
* According to RFC 7950, sec 5.6.6 (3rd paragraph) [ED: 5.6.5?],
when an implemented module augments another module
(ietf-interfaces), the augmented module MUST be also
implemented. So libyang automatically changes the augmented
module from imported to the implemented. The same rule applies
also in case of referring a module in path (leafref) and
by deviating a module. But it does not apply when a module
data is used in must or when conditions. That's the reason why
it complains just about ietf-ip and not about ietf-interfaces.
* YANG actually does not provide a way to specify that a
particular import is also expected to be implemented.
Therefore, libyang needs some help with setting modules
implemented - all the explicitly loaded modules are supposed
to be implemented, if the module is just implicitly loaded
from the search directory and user did not expressed that it
is supposed to be implemented, it is kept only imported to
provide groupings or type definitions
5. Benoit Claise asked (referring to my reference to automated tools):
* Would it be possible to improve the warning (and the related
test, by testing implemented instead of import), basically
telling that the module itself is fine?
I’m interested to know that NETMOD thinks about this distinction
between implemented versus imported (in the absence of any instance
documents). I guess my (maybe naive) view is that if all I’m doing is
checking for errors in my YANG model then I don’t care about this. If
my YANG is good I want to see no warnings or errors, and if it’s bad
then I want to be told this (and why).
Thanks,
William
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