Deprecate series in bundles

[jack-w-shaw]

Show a deprecation warning when deploying a bundle with series

We are deprecating series in favour of base in general. In Juju 4.0 we will error out if a bundle provides a base. This change in in preparation for this later breaking change

Checklist

• Code style: imports ordered, good names, simple structure, etc
• Comments saying why design decisions were made
• Go unit tests, with comments saying what you're testing
• Integration tests, with comments saying what you're testing
• doc.go added or updated in changed packages

QA steps

Deploy some bundles

$ cat ./bundle.yaml
series: focal
applications:
  ubuntu:
    charm: ubuntu
    num_units: 1
    to:
    - "0"
machines:
  "0":

$ juju deploy ./bundle.yaml
WARNING series in being deprecated in favour of bases. For more information about the transition to bases see https://discourse.charmhub.io/t/transition-from-series-to-base-in-juju-4-0/14127
...

$ cat bundle.yaml 
applications:
  ubuntu:
    series: focal
    charm: ubuntu
    num_units: 1
    to:
    - "0"
machines:
  "0":
    base: ubuntu@20.04

$ juju deploy ./bundle.yaml
WARNING series in being deprecated in favour of bases. For more information about the transition to bases see https://discourse.charmhub.io/t/transition-from-series-to-base-in-juju-4-0/14127
...

$ cat bundle.yaml 
applications:
  ubuntu:
    base: ubuntu@20.04
    charm: ubuntu
    num_units: 1
    to:
    - "0"
machines:
  "0":
    series: focal

$ juju deploy ./bundle.yaml
WARNING series in being deprecated in favour of bases. For more information about the transition to bases see https://discourse.charmhub.io/t/transition-from-series-to-base-in-juju-4-0/14127
...

$ cat ./bundle.yaml
series: focal
default-base: ubuntu@20.04
applications:
  ubuntu:
    charm: ubuntu
    num_units: 1
    to:
    - "0"
machines:
  "0":

$ juju deploy ./bundle.yaml
WARNING series in being deprecated in favour of bases. For more information about the transition to bases see https://discourse.charmhub.io/t/transition-from-series-to-base-in-juju-4-0/14127
...

default-base: ubuntu@20.04
applications:
  ubuntu:
    charm: ubuntu
    num_units: 1
    to:
    - "0"
machines:
  "0":

$ juju deploy ./bundle.yaml
...

$ juju deploy charmed-kubernetes
Located bundle "charmed-kubernetes" in charm-hub, revision 1243
WARNING series in being deprecated in favour of bases. For more information about the transition to bases see https://discourse.charmhub.io/t/transition-from-series-to-base-in-juju-4-0/14127
...

Links

Jira card: JUJU-5596

[SimonRichardson]

I'm not a fan of doing this in 3.1, as we've already released this. We should be doing things with "The Principle of Least Surprise". If the user deployed a bundle yesterday with no warning and if the user got an automatic snap refresh and deployed the same bundle today, they get a warning, that's concerning.

I think this should have been in 3.5

[SimonRichardson]

Also if we do land this, we shouldn't use that text. As it's not only bundles that this issue concerns.

WARNING series is being deprecated in favor of base. See ... for more information about the transition to bases.

[jack-w-shaw]

I'm not a fan of doing this in 3.1, as we've already released this. We should be doing things with "The Principle of Least Surprise". If the user deployed a bundle yesterday with no warning and if the user got an automatic snap refresh and deployed the same bundle today, they get a warning, that's concerning.

I think this should have been in 3.5

Not sure if I agree this principle applies for a deprecation warning. The reason I picked 3.1 is to socialise this warning to as many people as possible. If someone has only been using 3.1 and they're 'surprised' by this warning after a snap refresh, that's probably a good thing

Especially given the warning specifically mentions the version this functionality will be released. A user running 3.1 who suddenly sees this will quite quickly realise it won't affect them until a later major version

[jack-w-shaw]

Also if we do land this, we shouldn't use that text. As it's not only bundles that this issue concerns.

WARNING series is being deprecated in favor of base. See ... for more information about the transition to bases.

Yes I should probably create a discourse post highlighting all the differences

[SimonRichardson]

Especially given the warning specifically mentions the version this functionality will be released. A user running 3.1 who suddenly sees this will quite quickly realise it won't affect them until a later major version

Also, it will warn them every single time, as the person who deploys might not be the author of the charm. Something to consider.

[jack-w-shaw]

/merge