Why are most Python dependencies use depends_lib?

[Mojca Miklavec]

On Sat, 8 Sep 2018 at 06:17, Ryan Schmidt wrote:
> On Sep 7, 2018, at 22:08, Chih-Hsuan Yen wrote:
>
> > Thank you both for explanations and reasoning! As depends_run and
> > depends_lib are practically the same for Python ports, how about
> > moving all ports to either depends_lib or depends_run gradually?
> > Having two patterns hurts my eyes :D
> >
> > If we are moving to depends_run, just remember to keep non-Python
> > dependencies in depends_lib for Python packages with C extensions. For
> > example, in py-openssl, path:lib/libssl.dylib:openssl should be kept
> > in depends_lib and port:py${python.version}-cryptography and
> > port:py${python.version}-six can be moved to depends_run.
>
> I do not know enough about Python to confirm whether such a mass change would be appropriate. I thought some Python modules are compiled. If one compiled Python module depends on another compiled Python module, probably it does so at build time, not just at runtime; in other words, depends_lib would be correct for that case.

Indeed. While mass change is feasible, it should only be done if we
test one-by-one port (even if using some scripting to iterate through
ports), and for each port test whether a port can be compiled and
installed/destrooted without having a particular dependency available.
If that is the case, the dependency could be moved to depends_run.

To me it sounds correct to move dependencies from depends_lib to
depends_run, but only if they are not needed during build time. I
would probably not volunteer for that task though since it takes quite
some time to get this right and there is not so much advantage other
than consistency.

Mojca