is_effective_base_eol() crashes with UnknownVersionError on build-base: devel

[lengau]

Note: This issue was drafted by an AI assistant (GitHub Copilot CLI) on behalf of @lengau, based on investigation of a spread test failure in canonical/imagecraft.

Bug Description

ProjectService.is_effective_base_eol() does not handle a build-base/base of devel (or any base unrecognized by distro-support) the same way its sibling methods do, causing an unhandled UnknownVersionError crash.

Both check_base_is_supported() and base_eol_soon_date() already special-case or defensively catch this:

• check_base_is_supported() explicitly treats a devel series as always-supported:

  if build_base.series == "devel":
      build_base = None

• base_eol_soon_date() catches the error and assumes the base is supported:

  except (UnknownDistributionError, UnknownVersionError):
      # If distro-support doesn't know about this base, assume it's supported.
      return None

However, is_effective_base_eol() has neither protection:

def is_effective_base_eol(self) -> bool:
    """Determine whether the base on which to build is end-of-life."""
    base = craft_platforms.DistroBase.from_str(self.get().effective_base)
    return not self._is_supported_on(base=base, date=datetime.date.today())

This method is called from commands/lifecycle.py::_check_supported_base() specifically on the --ignore=unmaintained path:

if "unmaintained" in ignore_items:
    if project_service.is_effective_base_eol():
        ...

So any project with build-base: devel (or base: devel) that runs pack --ignore=unmaintained crashes with:

distro_support.errors.UnknownVersionError: Unknown version ubuntu devel

This is closely related to #986, but that issue was about an outdated pinned distro-support version for a real series (ubuntu@26.04), fixed by bumping the dependency. This case is different: devel is never going to be a version distro-support recognizes, so bumping the dependency won't fix it — the code path itself needs the same devel/UnknownVersionError handling used elsewhere.

To Reproduce

1. Create a project with:

   base: bare
   build-base: devel

2. Run <app> pack --ignore=unmaintained.

Relevant log output

imagecraft internal error: UnknownVersionError('Unknown version ubuntu devel')
Traceback (most recent call last):
  ...
  File ".../craft_application/commands/lifecycle.py", line 227, in _check_supported_base
    if project_service.is_effective_base_eol():
       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File ".../craft_application/services/project.py", line 761, in is_effective_base_eol
    base = craft_platforms.DistroBase.from_str(self.get().effective_base)
  File ".../craft_application/services/project.py", line 694, in _is_supported_on
    support_range = distro_support.get_support_range(base.distribution, base.series)
  File ".../distro_support/__init__.py", line 19, in get_support_range
    raise UnknownVersionError(distribution, version)
distro_support.errors.UnknownVersionError: Unknown version ubuntu devel

Suggested fix

Give is_effective_base_eol() the same treatment as check_base_is_supported()/base_eol_soon_date(): treat a devel series as always-supported (not EOL), and/or catch (UnknownDistributionError, UnknownVersionError) and assume the base is supported when distro-support doesn't recognize it.