Should python-daemon be a required package for installing the SSM via the setup.py script?

[gregcorbett]

Currently it's only an optional requirement in setup.py but a hard requirement in apel-ssm.spec.

[gregcorbett]

If it remains an optional requirement in setup.py, L61 should be changed to:

'receiver': ['python-daemon'],

as it seems pip ignores extras with special characters, i.e. - (pypa/pip#3810 and pypa/pip#4037).

Examples below.

$ grep -A 2 "extras_require" setup.py
          extras_require={
              'python-daemon': ['python-daemon'],
          },

$ sudo pip install apel-ssm[python-daemon]
Requirement already satisfied (use --upgrade to upgrade): apel-ssm[python-daemon] in /usr/lib/python2.7/site-packages/apel_ssm-2.2.0-py2.7.egg
  apel-ssm 2.2.0 does not provide the extra 'python-daemon'

$ grep -A 2 "extras_require" setup.py
          extras_require={
              'receiver': ['python-daemon'],
          },

$ sudo pip install apel-ssm[receiver]
Requirement already satisfied (use --upgrade to upgrade): apel-ssm[receiver] in /usr/lib/python2.7/site-packages/apel_ssm-2.2.0-py2.7.egg
...
Installing collected packages: python-daemon
Successfully installed python-daemon-2.1.2

[tofu-rocketry]

I guess we should follow what @jrha says for this kind of thing - if a package is optional then it shouldn't be a requirement and, as there's no consistent way of handling optionals across packaging systems, then it should just be left out.

The flip side of this is that we probably need better exception handling if the packages are missing when an attempt is made to use the parts of our software that do need those packages.

[gregcorbett]

Closing this issue as my question has been answered. Opened #80 to document that a change should be made.