[4.0.4][strict] usage of the python plugin forces the python3 interpreter to be shipped in the snap

[Dmitrii Shcherbakov]

The python plugin uses the following command to set up a venv in the installation directory:

https://github.com/snapcore/snapcraft/blob/4.0.4/snapcraft/plugins/v2/python.py#L117-L120
${SNAPCRAFT_PYTHON_INTERPRETER}" -m venv ${SNAPCRAFT_PYTHON_VENV_ARGS} "${SNAPCRAFT_PART_INSTALL}

This forces python3 to be copied into the snap without any explicit configuration:

snapcraft-microstack # stat parts/openstack-projects/install/bin/python3
  File: parts/openstack-projects/install/bin/python3 -> /root/stage/bin/python3
  Size: 23 Blocks: 0 IO Block: 4096 symbolic link
Device: 10fc80h/1113216d Inode: 7210747 Links: 1
Access: (0777/lrwxrwxrwx) Uid: ( 0/ root) Gid: ( 0/ root)
Access: 2020-06-10 17:27:10.515782934 +0000
Modify: 2020-06-10 17:27:10.511782914 +0000
Change: 2020-06-10 17:27:10.511782914 +0000
 Birth: -

snapcraft-microstack # rm parts/openstack-projects/install/bin/python3

snapcraft-microstack # "${SNAPCRAFT_PYTHON_INTERPRETER}" -m venv ${SNAPCRAFT_PYTHON_VENV_ARGS} "${SNAPCRAFT_PART_INSTALL}"
snapcraft-microstack # stat parts/openstack-projects/install/bin/python3
  File: parts/openstack-projects/install/bin/python3 -> /root/stage/bin/python3
  Size: 23 Blocks: 0 IO Block: 4096 symbolic link
Device: 10fc80h/1113216d Inode: 7210747 Links: 1
Access: (0777/lrwxrwxrwx) Uid: ( 0/ root) Gid: ( 0/ root)
Access: 2020-06-10 17:27:28.487873571 +0000
Modify: 2020-06-10 17:27:28.483873551 +0000
Change: 2020-06-10 17:27:28.483873551 +0000
 Birth: -

Meanwhile, I would like to avoid this and the one shipped with core20.

And at runtime the lack of that leads to subtle failures like this:

# a shell in the snap environment:
# sha256sum /usr/bin/python3.8
3fe2b9781ccb82b2a143cdcac2630ff25a74e049d5f34d6c10edd0598ccb705f /usr/bin/python3.8

# sha256sum /snap/microstack/x11/bin/python3
3fe2b9781ccb82b2a143cdcac2630ff25a74e049d5f34d6c10edd0598ccb705f /snap/microstack/x11/bin/python3

# python3.8
Python 3.8.2 (default, Apr 27 2020, 15:53:34)
[GCC 9.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import keystone
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ModuleNotFoundError: No module named 'keystone'

>>> import sys
>>> sys.path
['', '/usr/lib/python38.zip', '/usr/lib/python3.8', '/usr/lib/python3.8/lib-dynload', '/usr/lib/python3/dist-packages']

# python3
Python 3.8.2 (default, Apr 27 2020, 15:53:34)
[GCC 9.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import keystone
>>> import sys
>>> sys.path
['', '/usr/lib/python38.zip', '/usr/lib/python3.8', '/usr/lib/python3.8/lib-dynload', '/snap/microstack/x11/lib/python3.8/site-packages']

# outside the confined environment:

$ sha256sum /snap/core20/current/usr/bin/python3
3fe2b9781ccb82b2a143cdcac2630ff25a74e049d5f34d6c10edd0598ccb705f /snap/core20/current/usr/bin/python3

$ sha256sum /snap/core20/current/bin/python3
3fe2b9781ccb82b2a143cdcac2630ff25a74e049d5f34d6c10edd0598ccb705f /snap/core20/current/bin/python3

$ sha256sum /snap/microstack/current/bin/python3
05d75e4d16006f760b67b0901587f0f94dace6b7231e1351c1349ecbb0ebaf4c /snap/microstack/current/bin/python3

[Sergio Schvezov (sergiusens)]

We had a symlink issue in the past which caused *cyclic symlinking farm* that has since been solved, is this still an issue today?

[Launchpad Janitor (janitor)]

[Expired for Snapcraft because there has been no activity for 60 days.]