[Fedora-packaging] Re: Packaging python3-*-devel subpackages

[Petr Pisar]

V Fri, Feb 17, 2023 at 03:38:45PM +0100, Miro Hrončok napsal(a):
>  Hello Pythonistats and packaging folks.
>  
>  Tomáš (CCed) approached me today with an interesting question.
>  A Python package he is packaging into RPM (python3-rapidfuzz) installs some
>  development files (.h and .pxd).
>  
>  Tomáš queried upstream about those files to figure out if they should be
>  installed or if they are only needed to build the package itself. Upstream
>  responded:
>  
>  > rapidfuzz.h and __init__.pxd provide a capi for rapidfuzz, which allows users
>  > to write their own similarity metrics in C/C++/Cython, which can be called by
>  > rapidfuzz in a more performant way through this C-API.
>  > For this reason the header file should be part of the installation as well.
>  
>  OK, we want to ship them. Our packaging guidelines however say:
>  
>  https://docs.fedoraproject.org/en-US/packaging-guidelines/#_devel_packages
>  
>  > Specifically, -devel packages must be used to contain files which are
>  > intended solely for development or needed only at build-time. This is done to
>  > minimize the install footprint for users. There are some types of files which
>  > almost always belong in a -devel package:
>  >  - Header files...
>  
>  So from our guidelines perspective, the files would go to
>  python3-rapidfuzz-devel. The way we packaged Python in 201x, this would be
>  the end of it.
>  
>  However, in this decade with automatic Python BuildRequires, we could easily
>  end up in this situation:
>  
>   1. a Python package lists rapidfuzz as a build requirement
>   2. %pyproject_buildrequires generates a dependency on python3dist(rapidfuzz)
>   3. only python3-rapidfuzz is pulled
>   4. %build wants to use rapidfuzz.h
>   5. packager needs to manually BuildRequire python3-rapidfuzz-devel
>  
>  To avoid (5), my suggestion was to add the following requirement to
>  python3-rapidfuzz:
>  
>    Requires: (python3-rapidfuzz-devel%{?_isa} =
>               %{?epoch:%{epoch}:}%{version}-%{release} if python3-devel)
>  
>  That way, application packages that pull in pytohn3-rapidfuzz as a runtime
>  dependency won't get it (we are minimizing the install footprint for users),
>  but users who build stuff (including RPM packages) will get it (we make
>  automatically generated dependencies work as intended).
>  
>  (Of course, users who have python3-devel installed for reasons other than
>  rapidfuxx will still get the files, but the assumption here is that users
>  who install -devel packages intent to /generally/ build stuff.)
>  
>  Is that a good suggestion? And if so, should it be a general recommendation
>  for such cases?
>   
Originally I wrote a long reply and I found out that I'm in two minds and
deleted it.

Now thinking more on it, I conclude that the only effect of the proposal is to
make Fedora packaging compatible with upstream (installing Python modules with
pip, automatic generation of Fedora packages) at the expense of forcing users
to install the devel subpackage.

The reasoning is this: If the devel package is small (size- and
dependency-wise), it's content could be merged into a main package and
nobody would notice. If the devel package is large, then it would matter,
especially to people who do not want to install it. And that's exactly the
situation where a downstream's packaging differing from upstream is the raison
d'être for existence of the downstream itself.

Try to answer why we do not put Requires: (openssl-devel if gcc) to
openssl-libs.

Therefore I recommend not to require adding the dependency. Instea, the
packager should evaluate whether the feature is essential or optional, and do
not split it from the main package, or split it without conditions.

-- Petr