build_charm should return Path object

[paulomach]

Issue

pytest_operator.Ops_Test.build_charm return type is pathlib.Path
pytest_operator_cache.Ops_Test.build_charm return type is str

Tests relying on a charm with as Path object will fail on CI only.

[github-actions]

https://warthogs.atlassian.net/browse/DPE-2432

[carlcsaposs-canonical]

Could you elaborate more on your use case?

ops_test.model.deploy from python-libjuju expects a str, not a path: https://github.com/juju/python-libjuju/blob/f21bc426952579efb980439f6a07d59bcb4cce0b/juju/model.py#L1670

python-libjuju contains a workaround for the non-conformant type signature in pytest-operator to cast the path to a string. However, it will fail to detect that the string is for a local charm (instead of a charm from charmhub) unless the path is resolved to an absolute path.

If possible, I'd prefer to avoid using this workaround since I'm worried it might introduce instabilities. I'd prefer to return a value that python-libjuju/juju expects—e.g. "./foo.charm" for a local charm.

However, if your use case requires a path, we should revisit this