Builds of charm using reactive plugin produces different config option

[chanchiwai-ray]

Bug Description

Take https://github.com/canonical/charm-juju-local for example, after updating the charmcraft.yaml to the syntax to what charmcraft 3 supports:

type: charm
parts:
  charm:
    source: .
    plugin: reactive
    build-snaps: [charm/2.x/stable]
platforms:
  [email protected]:amd64:
  [email protected]:amd64:

The produced charm file will have different config.yaml than what was build using charmcraft 2

diff charmcraft2/config.yaml charmcraft3/config.yaml 
1,47c1,8
< # Copyright 2016 Canonical Ltd.
< #
< # This file is part of the Snap layer for Juju.
< #
< # Licensed under the Apache License, Version 2.0 (the "License");
< # you may not use this file except in compliance with the License.
< # You may obtain a copy of the License at
< #
< #  http://www.apache.org/licenses/LICENSE-2.0
< #
< # Unless required by applicable law or agreed to in writing, software
< # distributed under the License is distributed on an "AS IS" BASIS,
< # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
< # See the License for the specific language governing permissions and
< # limitations under the License.
< "options":
<   # snap_proxy and snap_proxy_url have been deprecated for some time.
<   # If your charm still needs them, add these config items manually
<   # to your charm's config.yaml.
<   # snap_proxy:
<   #   description: >
<   #     DEPRECATED. Use snap-http-proxy and snap-https-proxy model configuration settings.
<   #     HTTP/HTTPS web proxy for Snappy to use when accessing the snap store.
<   #   type: string
<   #   default: ""
<   # snap_proxy_url:
<   #   default: ""
<   #   type: string
<   #   description: >
<   #     DEPRECATED. Use snap-store-proxy model configuration setting.
<   #     The address of a Snap Store Proxy to use for snaps e.g. http://snap-proxy.example.com
<   "snapd_refresh":
<     "default": ""
<     "type": "string"
<     "description": >
<       How often snapd handles updates for installed snaps. The default
<       (an empty string) is 4x per day. Set to "max" to check once per month
<       based on the charm deployment date. You may also set a custom string as
<       described in the 'refresh.timer' section here:
<         https://forum.snapcraft.io/t/system-options/87
<   "juju-channel":
<     "default": "2.9/stable"
<     "type": "string"
<     "description": |-
<       The channel of juju snap to install. Default to 2.9/stable.
<       Note: This value needs to be set at deployment time. Changes made
<       post-deployment will not be taken into effect.
---
> options:
>   juju-channel:
>     default: "2.9/stable"
>     type: string
>     description: |
>         The channel of juju snap to install. Default to 2.9/stable.
>         Note: This value needs to be set at deployment time. Changes made
>         post-deployment will not be taken into effect.
\ No newline at end of file

The difference in the config.yaml causes error during the installation of the charm

unit-juju-local-0: 2025-02-24 06:55:11 ERROR unit.juju-local/0.juju-log Hook error:
Traceback (most recent call last):
  File "/var/lib/juju/agents/unit-juju-local-0/.venv/lib/python3.10/site-packages/charms/reactive/__init__.py", line 74, in main
    bus.dispatch(restricted=restricted_mode)
  File "/var/lib/juju/agents/unit-juju-local-0/.venv/lib/python3.10/site-packages/charms/reactive/bus.py", line 390, in dispatch
    _invoke(other_handlers)
  File "/var/lib/juju/agents/unit-juju-local-0/.venv/lib/python3.10/site-packages/charms/reactive/bus.py", line 359, in _invoke
    handler.invoke()
  File "/var/lib/juju/agents/unit-juju-local-0/.venv/lib/python3.10/site-packages/charms/reactive/bus.py", line 181, in invoke
    self._action(*args)
  File "/var/lib/juju/agents/unit-juju-local-0/charm/reactive/snap.py", line 345, in change_snapd_refresh
    timer = hookenv.config()["snapd_refresh"]
KeyError: 'snapd_refresh'

To Reproduce

git clone https://github.com/canonical/charm-juju-local

1. Use charmcraft 2 (2.x/stable) to pack the charm, and unzip the charm file.
2. Update the charmcraft.yaml as the following (see below) . Then ,use charmcraft 3 (3.x/stable) to pack the charm, and unzip the charm file.
3. Compare the config.yaml between the two builds

Environment

Name                            Version                     Rev    Tracking            Publisher            Notes
charm                           3.0.7                       745    3.x/stable          canonical✓           classic
charmcraft                      3.4.2                       5977   3.x/stable          canonical✓           classic
...

charmcraft.yaml

type: charm
parts:
  charm:
    source: .
    plugin: reactive
    build-snaps: [charm/2.x/stable]
platforms:
  [email protected]:amd64:
  [email protected]:amd64:

Relevant log output

unit-juju-local-0: 2025-02-24 06:55:11 ERROR unit.juju-local/0.juju-log Hook error:
Traceback (most recent call last):
  File "/var/lib/juju/agents/unit-juju-local-0/.venv/lib/python3.10/site-packages/charms/reactive/__init__.py", line 74, in main
    bus.dispatch(restricted=restricted_mode)
  File "/var/lib/juju/agents/unit-juju-local-0/.venv/lib/python3.10/site-packages/charms/reactive/bus.py", line 390, in dispatch
    _invoke(other_handlers)
  File "/var/lib/juju/agents/unit-juju-local-0/.venv/lib/python3.10/site-packages/charms/reactive/bus.py", line 359, in _invoke
    handler.invoke()
  File "/var/lib/juju/agents/unit-juju-local-0/.venv/lib/python3.10/site-packages/charms/reactive/bus.py", line 181, in invoke
    self._action(*args)
  File "/var/lib/juju/agents/unit-juju-local-0/charm/reactive/snap.py", line 345, in change_snapd_refresh
    timer = hookenv.config()["snapd_refresh"]
KeyError: 'snapd_refresh'

[lengau]

Thanks for the report! I think I know why this is occurring, but actually implementing the fix is going to require some research.

[syncronize-issues-to-jira]

Thank you for reporting your feedback to us!

The internal ticket has been created: https://warthogs.atlassian.net/browse/CRAFT-4206.

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