Local charm has channel specified

[Domas Monkus]

When deploying a juju bundle to a model with the bundle already deployed (to apply config changes), I get the following error:
```
ERROR cannot deploy bundle: application "filebeat": upgrades not supported across channels (existing: "stable", resolved: ""); use --force to override
```

Juju version: 2.9.27
Cloud: openstack

This is a mojo-controlled deployment with a collect phase, so all charms are deployed from local storage, however, they appear to be marked as coming from the stable channel:
```
(...)
 filebeat:
    charm: local:xenial/filebeat-1
    series: xenial
    os: ubuntu
    charm-origin: local
    charm-name: filebeat
    charm-rev: 1
    charm-channel: stable
(...)
```

The bundle itself does not specify the channel:
```
(...)
filebeat:
    charm: {{ build_dir }}/../charms/{{ series }}/filebeat
    options:
(...)
```

[Ian Booth (wallyworld)]

It seems wrong to me that local charms are having the channel set.

[Heather Lanigan (hmlanigan)]

Local charms won't use the channel, this is a cosmetic issue with the output of status. The juju db application has no channel set for local charms.

[Domas Monkus (tasdomas)]

This is obviously more than just a cosmetic issue, since it's preventing us from rolling out configuration changes.

[Domas Monkus (tasdomas)]

Also, from inspecting mojo logs, it looks like this wasn't an issue with juju 2.8.7 and happened after an upgrade to 2.9.21

[Heather Lanigan (hmlanigan)]

It's related to the work for integrating charmhub into juju, so specific to 2.9.

Please supply steps to reproduce outside of mojo.

[Domas Monkus (tasdomas)]

Sure.

# Let's start with a juju 2.8 controller
$ sudo snap install juju --channel 2.8/stable
$ mkdir t; cd t
$ charm pull cs:ubuntu
# copy attached bundle.yaml file
$ juju deploy ./bundle.yaml
$ juju status --yaml
(...)
applications:
  u:
    charm: local:focal/ubuntu-0
    series: focal
    os: ubuntu
    charm-origin: local
    charm-name: ubuntu # no charm-channel present
    charm-rev: 0
    exposed: false
(...)

# upgrade to 2.9
$ sudo snap refresh juju --channel 2.9/stable
$ juju upgrade-controller
$ juju status --format yaml
(...)
applications:
  u:
    charm: local:focal/ubuntu-0
    series: focal
    os: ubuntu
    charm-origin: local
    charm-name: ubuntu
    charm-rev: 0
    charm-channel: stable # oh, what is this?
    exposed: false
(...)

# ok, maybe it's just a cosmetic issue then
$ juju deploy ./bundle.yaml
ERROR cannot deploy bundle: application "u": upgrades not supported across channels (existing: "stable", resolved: ""); use --force to override

Nope, not cosmetic at all.

[Heather Lanigan (hmlanigan)]

This is related to the upgrade, though without it there are a different bugs it looks like.

2.9.30 in develop:

$ juju deploy ./bundle.yaml
Executing changes:
- upload charm /home/heather/notes/bug-1970608/ubuntu for series focal with architecture=amd64
- deploy application u on focal
- add unit u/0 to new machine 1
Deploy of bundle completed.
$ juju deploy ./bundle.yaml
Executing changes:
- set constraints for u to "" <-- why?
Deploy of bundle completed.
$ juju deploy ./bundle.yaml
No changes to apply. <-- replicated with juju 2.8.13
$ juju refresh u --path ./ubuntu
Added local charm "ubuntu", revision 1, to the model

[Heather Lanigan (hmlanigan)]

https://github.com/juju/juju/pull/14039