fix to decode JSON from response to get_facts

[chidanandpujar]

ROOT CAUSE & FIX SUMMARY

ROOT CAUSE

Ansible persistent connections use a JSON-RPC Unix socket. The connection plugin
process serializes return values via pickle.dumps(). When get_facts() returned
dict(self.dev.facts), the dict contained PyEZ junos.version_info namedtuple
objects which are not safely picklable. This caused the connection process to
crash without sending a socket reply. The caller received None from the socket,
which json.loads('None') could not parse, producing:

"Unable to decode JSON from response to get_facts(). Received 'None'."

Secondary bug: PR #816 partially fixed this using json.dumps(..., default=str),
but str() converted namedtuples to opaque strings like
"junos.version_info(major=(25, 4), type=R, minor=1, build=12)" instead of
structured dicts, breaking version_info and junos_info[re0]['object'].

FILES MODIFIED

1. plugins/connection/pyez.py

   a) Added module-level helper before class Connection:

   def _serialize_fact(obj):
   if hasattr(obj, "_fields"): # namedtuple
   return dict(zip(obj._fields, obj))
   return str(obj)

   Converts junos.version_info namedtuples to plain dicts
   e.g. {"major": [25, 4], "type": "R", "minor": 1, "build": 12}
   Falls back to str() only for truly unknown types.

   b) Updated get_facts() method:

   @ensure_connect # guarantees device is connected
   def get_facts(self):
   facts = self.dev.facts
   if facts is None: # guard against None facts
   return {}
   return json.loads(json.dumps(dict(facts), default=_serialize_fact))

   Changes: added @ensure_connect, None guard, default=_serialize_fact
   (was: default=str, no decorator, no None guard)

2. plugins/modules/facts.py

   Added None guard in get_facts_dict() pyez path:

   else:
   facts = junos_module.get_facts()
   if facts is None: # <-- added
   facts = {} # <-- added

   Prevents KeyError/TypeError if get_facts() returns None.

Before fix:

[WARNING]: Deprecation warnings can be disabled by setting `deprecation_warnings=False` in ansible.cfg.
[DEPRECATION WARNING]: Importing 'to_bytes' from 'ansible.module_utils._text' is deprecated. This feature will be removed from ansible-core version 2.24. Use ansible.module_utils.common.text.converters instead.
[ERROR]: Task failed: Module failed: Unable to decode JSON from response to get_facts(). Received 'None'.

Task failed: Module failed.
Origin: /root/ansible_release_final/ansible-junos-stdlib/tests/pb.juniper_junos_facts.yml:6:7

4   gather_facts: false
5   tasks:
6     - name: "TEST 1 - Gather Facts"
        ^ column 7

<<< caused by >>>

Unable to decode JSON from response to get_facts(). Received 'None'.

fatal: [pyez_connection_testcases]: FAILED! => {
    "changed": false,
    "msg": "Task failed: Module failed: Unable to decode JSON from response to get_facts(). Received 'None'."
}
...ignoring

TASK [Check TEST 1] ******************************************************************************************************************
task path: /root/ansible_release_final/ansible-junos-stdlib/tests/pb.juniper_junos_facts.yml:12
[ERROR]: Task failed: Action failed: Assertion failed
Origin: /root/ansible_release_final/ansible-junos-stdlib/tests/pb.juniper_junos_facts.yml:12:7

10
11
12     - name: Check TEST 1
         ^ column 7

fatal: [pyez_connection_testcases]: FAILED! => {
    "assertion": "test1.facts.hostname is defined and test1.facts.hostname | length > 0",
    "changed": false,
    "evaluated_to": false,
    "msg": "Assertion failed"
}

PLAY RECAP ***************************************************************************************************************************
pyez_connection_testcases  : ok=1    changed=0    unreachable=0    failed=1    skipped=0    rescued=0    ignored=1 

After fix:

(relfinal) root@masterhost:~/ansible_release_final/ansible-junos-stdlib/tests# ansible-playbook -i inventory pb.juniper_junos_facts.yml 

PLAY [Test juniper.device.facts module] **********************************************************************************************

TASK [TEST 1 - Gather Facts] *********************************************************************************************************
[WARNING]: Deprecation warnings can be disabled by setting `deprecation_warnings=False` in ansible.cfg.
[DEPRECATION WARNING]: Importing 'to_bytes' from 'ansible.module_utils._text' is deprecated. This feature will be removed from ansible-core version 2.24. Use ansible.module_utils.common.text.converters instead.
ok: [pyez_connection_testcases]

TASK [Check TEST 1] ******************************************************************************************************************
ok: [pyez_connection_testcases] => {
    "changed": false,
    "msg": "All assertions passed"
}

TASK [TEST 2 - get facts in xml format] **********************************************************************************************
ok: [pyez_connection_testcases]

TASK [Check TEST 2] ******************************************************************************************************************
ok: [pyez_connection_testcases] => {
    "changed": false,
    "msg": "All assertions passed"
}

PLAY RECAP ***************************************************************************************************************************
pyez_connection_testcases  : ok=4    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0