Summary
With ansible-core 2.20 a filter plugin using Python's dataclasses module with caller-provided values raises UnsupportedConstructionMethodError ("Direct construction of lazy containers is not supported.") for lists and dictionaries.
Similar to #85606.
Issue Type
Bug Report
Component Name
_lazy_containers
Ansible Version
$ ansible --version
ansible [core 2.20.5]
config file = None
configured module search path = ['<redacted>/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
ansible python module location = /usr/local/lib/python3.13/dist-packages/ansible
ansible collection location = <redacted>/.ansible/collections:/usr/share/ansible/collections
executable location = /usr/local/bin/ansible
python version = 3.13.5 (main, Jun 25 2025, 18:55:22) [GCC 14.2.0] (/usr/bin/python3)
jinja version = 3.1.6
pyyaml version = 6.0.3 (with libyaml v0.2.5)
Configuration
# if using a version older than ansible-core 2.12 you should omit the '-t all'
$ ansible-config dump --only-changed -t all
CONFIG_FILE() = None
EDITOR(env: EDITOR) = /usr/bin/nano
PAGER(env: PAGER) = /usr/bin/less
GALAXY_SERVERS:
OS / Environment
Debian 13 (Trixie) with Ansible installed via Python pip.
Steps to Reproduce
Playbook:
- hosts: localhost
gather_facts: false
connection: local
vars:
literal: hello world
mylist:
- a
- b
mydict:
first: hello
second: world
tasks:
# Working
- debug: msg="{{ literal | bug }}"
# Failing
- debug: msg="{{ mylist | bug }}"
- debug: msg="{{ mydict | bug }}"filter_plugins/test.py:
import dataclasses
@dataclasses.dataclass()
class _Data:
value: dict
def bug(value):
return dataclasses.asdict(_Data(value=value))
class FilterModule:
def filters(self):
return {"bug": bug}Expected Results
ok: [localhost] => {
"msg": {
"value": "hello world"
}
}
ok: [localhost] => {
"msg": {
"value": ["a", "b"]
}
}
ok: [localhost] => {
"msg": {
"value": {"first": "hello", "second": "world"}
}
}
Actual Results
PLAY [localhost] **********************************************************************************************************************************************
TASK [debug] **************************************************************************************************************************************************
ok: [localhost] => {
"msg": {
"value": "hello world"
}
}
TASK [debug] **************************************************************************************************************************************************
[ERROR]: Task failed: Finalization of task args for 'ansible.builtin.debug' failed: Error while resolving value for 'msg': The filter plugin 'bug' failed: Direct construction of lazy containers is not supported.
Task failed: Finalization of task args for 'ansible.builtin.debug' failed.
Origin: <redacted>/temp/ansible-lazy-direct-construction/playbook.yml:17:7
15
16 # Failing
17 - debug: msg="{{ mylist | bug }}"
^ column 7
<<< caused by >>>
Error while resolving value for 'msg': The filter plugin 'bug' failed: Direct construction of lazy containers is not supported.
Origin: <redacted>/temp/ansible-lazy-direct-construction/playbook.yml:17:14
15
16 # Failing
17 - debug: msg="{{ mylist | bug }}"
^ column 14
fatal: [localhost]: FAILED! => {"msg": "Task failed: Finalization of task args for 'ansible.builtin.debug' failed: Error while resolving value for 'msg': The filter plugin 'bug' failed: Direct construction of lazy containers is not supported."}
PLAY RECAP ****************************************************************************************************************************************************
localhost : ok=1 changed=0 unreachable=0 failed=1 skipped=0 rescued=0 ignored=0Code of Conduct
Summary
With ansible-core 2.20 a filter plugin using Python's
dataclassesmodule with caller-provided values raisesUnsupportedConstructionMethodError("Direct construction of lazy containers is not supported.") for lists and dictionaries.Similar to #85606.
Issue Type
Bug Report
Component Name
_lazy_containers
Ansible Version
Configuration
OS / Environment
Debian 13 (Trixie) with Ansible installed via Python pip.
Steps to Reproduce
Playbook:
filter_plugins/test.py:Expected Results
Actual Results
Code of Conduct