sysrepo: Delete operation on operational on a leaf-list element in a module container tagged with config false does nothing

Hi,

I’ve been running in a problem, whenever I have a leaf-list (of string for the example) inside a container tagged with config false;, any delete operation on a leaf-list element ends up doing absolutely nothing.

• libyang 2.40.4 (branch devel)
• libsysrepo 7.19.12 (branch devel)

How to reproduce

• Install libyang
  • git clone https://github.com/CESNET/libyang.git
  • cd libyang
  • mkdir build
  • cd build
  • cmake …
  • make install -j
• Install sysrepo/libsysrepo
  • git clone https://github.com/sysrepo/sysrepo.git
  • cd sysrepo
  • mkdir build
  • cd build
  • cmake …
  • make install -j

(For this example I’ll use sysrepo-python, so you need to install it pip install sysrepo)

• Create a test.yang file with:

module test-module {
  yang-version 1.1;
  namespace "http://example.com/test-module";
  prefix test;

  container container {
    config false;
    leaf-list string-list {
        type string;
        description "a dummy string";
    }
  }
}

• Install the test.yang module

  • sysrepoctl -i test.yang

• Create a little python script to manipulate the operational datastore

  • manage_operational.py

#!/usr/bin/env python3

import sysrepo
import sys
import os

conn = sysrepo.connection.SysrepoConnection()
ds = 'operational'
session = conn.start_session(ds)
print("connected")

while True:
    try:
        s = input("'action xpath': ")
    except:
        break
    try:
        command = s.split(' ')
        while len(command) != 3:
            command.append('')
        action, xpath, value = command
        if action == 'get':
            values = session.get_items(xpath, no_subs=True)
            for value in values:
                print(value)
        elif action == 'delete':
            session.delete_item(xpath)
            session.apply_changes()
        elif action == 'set':
            session.set_item(xpath, value)
            session.apply_changes()
        elif action == 'quit':
            break
    except Exception as e:
        print(f'{s}: {e}')

This script gives 3 commands:
- get <xpath>
- delete <xpath>
- set <xpath> <value>

• Run the manage_operational.py script

  • python3 manage_operational.py

• Create leaf-list elements from manage_operational.py CLI

  • > set /test-module:container/string-list test_value1
  • > set /test-module:container/string-list test_value2
  • > set /test-module:container/string-list test_value3

• See if elements are created

  • > get /test-module:container/string-list or sysrepocfg --export -d operational

• We can see 3 elements now, test_value1, test_value2 and test_value3

• Delete one of them from manage_operational.py CLI

  • > delete /test-module:container/string-list[.='test_value1']

• See if element is deleted

  • > get /test-module:container/string-list or sysrepocfg --export -d operational

• It’s still there 😢

Note that THIS EXACT same deletion works if config false; is not present in the test.yang file.

Origin of the behavior

In sr_delete_item the deletion node operation:remove is added correctly in the edit tree. In sr_apply_changes, in sr_edit_merge_r, the function tries to find the trg_node with sr_edit_find_match. In sr_edit_find_match, sysrepo uses the macro lysc_is_dup_inst_list

#define lysc_is_dup_inst_list(lysc_node) \
    ((lysc_node && (((lysc_node->nodetype == LYS_LIST) && (lysc_node->flags & LYS_KEYLESS)) || \
            ((lysc_node->nodetype == LYS_LEAFLIST) && !(lysc_node->flags & LYS_CONFIG_W)))) ? 1 : 0)

As you can see, this define does not return 1 if the leaf-list is not in a container flagged with LYS_CONFIG_W This flag is set with config true;.

This behavior seems pretty strange, it might be me not understanding the correct behavior of config false; on operational but we do not want to change it in our yang file.

What do you think ?