Validation does not catch missing mandatory leaf

[lukasmacko]

Missing mandatory leaf is not detected in a sibling subtree by lyd_validate function. However, invalid data can not be loaded by lyd_parse_path.
libyang version 0.8.54

#include <stdio.h>
#include <stdlib.h>
#include <libyang/libyang.h>

#define XPATH "/ietf-interfaces:interfaces/interface[name='gigaeth0']/ietf-ip:ipv6/address[ip='fe80::ab8']/prefix-length"


int main(int argc, char **argv)
{
   /* create context load module*/
   struct ly_ctx *ctx = ly_ctx_new(".");
   lys_parse_path(ctx, "iana-if-type.yin", LYS_IN_YIN);
   const struct lys_module *module = lys_parse_path(ctx, "ietf-ip@2014-06-16.yin", LYS_IN_YIN);
   if (NULL == module) {
      return 1;
   }

   /* load data file*/
   struct lyd_node *root = lyd_parse_path(ctx, "data.xml", LYD_XML, LYD_OPT_STRICT | LYD_OPT_CONFIG);
   if (NULL == root || 0 != lyd_validate(&root, LYD_OPT_STRICT | LYD_OPT_NOAUTODEL | LYD_OPT_CONFIG)){
      puts("Validation failed");
      return 2;
   }

   /* remove mandatory element */
   struct ly_set *set = lyd_get_node(root, XPATH);
   if (NULL == set || set->number < 1){
      return 3;
   }
   lyd_unlink(set->set.d[0]);
   lyd_free(set->set.d[0]);

   /* VALIDATION SHOULD FAIL !!!*/
   if (0 != lyd_validate(&root, LYD_OPT_STRICT | LYD_OPT_NOAUTODEL | LYD_OPT_CONFIG)){
      puts("Validation failed");
      return 4;
   }

   /* write invalid content */   
   FILE *f = fopen("out.xml", "w");
   if (NULL == f) {
     return 5;
   }
   if (0 != lyd_print_file(f, root, LYD_XML, LYP_WITHSIBLINGS | LYP_FORMAT)){
      return 6;
   }

   /* unable to load "valid" written content */
   struct lyd_node *edited = lyd_parse_path(ctx, "out.xml", LYD_XML, LYD_OPT_STRICT | LYD_OPT_CONFIG);
   if (NULL == edited){
      puts("Error");
      return 7;
   }

   ly_set_free(set);
   lyd_free_withsiblings(root);
   ly_ctx_destroy(ctx, NULL);
   return 0;

}

data.xml

<interfaces xmlns="urn:ietf:params:xml:ns:yang:ietf-interfaces">
  <interface>
    <name>eth0</name>
    <description>Ethernet 0</description>
    <type>ethernetCsmacd</type>
    <enabled>true</enabled>
    <ipv4 xmlns="urn:ietf:params:xml:ns:yang:ietf-ip">
      <enabled>true</enabled>
      <mtu>1500</mtu>
      <address>
        <ip>192.168.2.100</ip>
        <prefix-length>24</prefix-length>
      </address>
    </ipv4>
  </interface>
  <interface>
    <name>eth1</name>
    <description>Ethernet 1</description>
    <type>ethernetCsmacd</type>
    <enabled>true</enabled>
    <ipv4 xmlns="urn:ietf:params:xml:ns:yang:ietf-ip">
      <enabled>true</enabled>
      <mtu>1500</mtu>
      <address>
        <ip>10.10.1.5</ip>
        <prefix-length>16</prefix-length>
      </address>
    </ipv4>
  </interface>
  <interface>
    <name>gigaeth0</name>
    <description>GigabitEthernet 0</description>
    <type>ethernetCsmacd</type>
    <enabled>false</enabled>
    <ipv6 xmlns="urn:ietf:params:xml:ns:yang:ietf-ip">
      <address>
        <ip>fe80::ab8</ip>
        <prefix-length>64</prefix-length>
      </address>
    </ipv6>
  </interface>
</interfaces>

Used .yin files can be found here