Bug 1821486

We have a %py3_dist macro in Fedora. It evaluates to python3dist(...)

In Fedora, we want python3dist() to be buildrequired, not python3.8dist(), because we want a SRPM created on Fedora 31 to be buildable on Fedora 33. Hence "hardcoding" the Python version to the generated buildrequires of that SRPM is a problem. Hence, the current behavior makes perfect sense.


If we add multiple Python stacks and we want to be able to have a "hardcoded Python version" specfile, the requirements rapidly change.


Consider the following spec snippet:

  %global python3_pkgversion 39
  %global __python3 %{_bindir}/python3.9
  ...
  BuildRequires:  %{py3_dist foo}

This buildrequires python3dist(foo) while it should really buildrequire python3.9dist(foo).

We could provide an alternate version of the macro, called %py3X_dist that does exactly that. However, the specfile could no longer remain "identical" because in regular specfiles, we would need to use %py3_dist and in special specfiles like this, %py3X_dist.

There are 2 possible ways out of this:

 1) Modify the behavior of %py3_dist -- when %python3_pkgversion is 3, it produces python3dist(), when %python3_pkgversion is 39, it produces python3.9dist()

 2) Keep %py3_dist as is, create %py3X_dist to work as described in (1).


A slight problem with both approaches is to derive 3.9 from 39. We could either:

 - stick a dot after the first "3" (works fine but feels very hackish)
 - add provides for python39dist() and use those (but the provides keep piling up)
 - use %python3_version if %python3_pkgversion is not 3 (this is fragile in case %python3_pkgversion is set, but not %__python3)
 - require yet another macro to be defined (e.g. %__py3_dist_version)

The last approach is the most flexible one, but it would require the specs to have 3 global defines:

  %global python3_pkgversion 39
  %global __python3 %{_bindir}/python3.9
  %global __py3_dist_version 3.9

That's starting to be complicated... but we can have a high level macro for this that does all of those and possibly others needed for the future, something like:


  %{python3_version_is 3.9}