Access klayout __version__ when loaded as python module

[qpavsmi]

It would be convenient for us if we could access the version string of the klayout module that is in use. A lot of python modules provide access through the use of __version__ member, I think this could be useful for klayout as well.

This might already be available and I just didn't read the klayout docs carefully enough :D But as far as I'm aware there is only the pya.Application.version member, which is not available when klayout is imported as a python module without running the klayout executable.

[qpavsmi]

Hi, spent an extra 5 seconds reading about importlib. It has version method for any module that is in use, which is sufficient for our needs :D This issue doesn't need to stay open for our sake

[klayoutmatthias]

Exactly. Honestly I thought that if I do setup.py a favour and tell it the version, it would also be able to return it to me. Apparently it took until Python 3.8 for this to become true :)

But your remark about pya.Application is valid. This is also true for Qt-less builds (not only Python), so I'll leave the ticket open and create a standard way of getting the version without pya.Application.

Thanks,

Matthias

[klayoutmatthias]

@thomaslima Thanks for the PR

I found a very simple solution while looking how other projects solve that problem: master...issue-1271

I personally like that the metadata (== version.sh) remains the single source of truth here. Is there an advantage using versioneer over this simple solution?

Thanks,

Matthias

[thomaslima]

@klayoutmatthias You are right. It's simpler. This is solution number 5 in the following guide: https://packaging.python.org/en/latest/guides/single-sourcing-package-version/

As you can see in the failed tests, the only caveat is that it is only available for python >= 3.8. It's backported as a package called importlib_metadata, so we need to install it for python < 3.8. I took the liberty to push a patch to your branch. Check it out.

[klayoutmatthias]

Perfect! Many thanks!

Best regards,

Matthias

[klayoutmatthias]

@thomaslima Azure fails with Python 3.6 with

ERROR: Could not find a version that satisfies the requirement importlib-metadata>=1.0; python_version < "3.8" (from klayout) (from versions: none)
ERROR: No matching distribution found for importlib-metadata>=1.0; python_version < "3.8"

I confirmed on Linux with Python 3.7 (3.6 is no longer available) that the approach basically works also for Python < 3.8.

Unfortunately the other Azure jobs terminate with too much CPU time, so it's difficult to say if the problem is specific to 3.6.

[thomaslima]

I just pushed a commit pinning importlib_metadata's version to 4.8.3. It was the last version supporting 3.6. Let's see if it will pass tests.