I finally got around to this mail...
On 2020-04-19 16:55, Miro Hrončok wrote:
Hello Python packagers.
After touching the %python_provide topic in:
https://lists.fedoraproject.org/archives/list/python-devel@lists.fedoraproject.org/thread/SSJLPWSGFGPYRSHXQZDR7JNQXSDGGX3Z/
I have realized several things I don't like about %python_provide:
1) It must be used conditionally (it is not defined in python-srpm-macros).
That means you always wrap it in %{?python_provide:...} in order to have
a "valid" specfile even when the macro is not yet defined (e.g. during
SRPM creation in Koji or on a packager's machine without
python-rpm-macros installed).
2) You cannot use it with arbitrary versions. Suppose you package
python3-foo 1.0 but you want to provide python3-bar 2.0 for some reason
-- this is not very common, but it happens. %python_provide only takes
the "name" as an argument, always using %{?epoch} %{version} and
%{release}.
3) You need to both add a virtual provide + use the macro. Suppose you
want to provide python3-pkg_resources from python3-setuptools.
Currently, you need to add:
Provides: python3-pkg_resources = %{version}-%{release}
%{?python_provide:%python_provide python3-pkg_resources}
4) When used with (sub)package name, it generates a duplicate dependency
on Fedora 33+ (and an rpmlint error).
5) It produces Obsoletes, but that might no longer be necessary nor
desired.
6) Broken expectations about %_isa. It used to add %_isa provides based
on wrong data, it no longer does that (except on old releases and
EPELs), can be used manually with name%{?_isa}, but not on the old
releases.
7) Undocuemnted error handling (e.g. the macro expands to nothing when
used with pypy-foo, but errors when used with foo).
Hence, I was thinking (for the sake of backwards compatibility) to
provide a new mechanism to do this and preserve the old macro as is,
deprecating it in Fedora 36-ish, actually maybe removing it once RHEL 9
goes EOL (or never, which is basically the same from today's perspective).
The new macro should solve the problems from above, my current (quick,
untested) ideas are:
1) Define the macro in python-srpm-macros. No need to use it
conditionally. We can backport it to EPEL 8 and define a "stub" macro in
EPEL 7 and 6. (An if we start using the macro only after Fedora 30 goes
EOL, we can make the macro behave consistently across all Fedora versions.)
2) Accept version identifier as an optional argument, use %{?epoch}
%{version} and %{release} as default. (See for example %{pypi_source} on
how this can be done.)
3) Make the macro also produce the provide for the given name and
document that. E.g. when you call it with python3-pkg_resources, it also
provides python3-pkg_resources (not only python-pkg_resources etc.).
4) Make it so that for given arguments, the macro will only expand to
something once per build. Hence when you use it with package name, the
automatic provides won't re-add the same provide again. This also means
you cannot have 2 different (sub)packages provide the same
name-version-release, but that shall be very very very uncommon need and
can always be workarounded somehow if needed.
5) No obsoletes with the new macro. Packagers use manual obsoletes when
desired.
6) Document clearly that there is no %{?_isa} (and there is no
"backwards compatibility" load to carry). When absolutely desired,
packagers can call the macro with %{name}%{?_isa}.
7) Support arbitrary names. Only provide the given name and nothing else
if not "recognized".
Is that better than erroring out when something is not recognized?
As a bonus, I think the current if-elif-elif-elif-elif code can be
replaced with lua patterns (imagine regex).
As always, this leaves us with the name problem, but I'd very much like
to use %python_provides (note the s). The only problem I see is that it
is likely to be mistaken for the old one, but IMHO it shouldn't really
hurt that much.
I guess something like %py_provides would also work, and maybe fit more
nicely with the new generation of macros. Do you like full "python" prefix?
But that's bikeshedding.
Usage example:
%package -n python3-setuptools
%python_provides python3-pkg_resources
Resulting provides:
python3-setuptools = 46.6.6-6.fc33
python-setuptools = 46.6.6-6.fc33
python39-pkg_resources = 46.6.6-6.fc33
python3-pkg_resources = 46.6.6-6.fc33
python-pkg_resources = 46.6.6-6.fc33
python39-pkg_resources = 46.6.6-6.fc33
I assume you meant "python39-setuptools" there.
Another example:
%package -n python3-pillow
%python_provides python3-PIL 1.1.6-100
Resulting provides:
python3-pillow = 7.1.1-1.fc33
python-pillow = 7.1.1-1.fc33
python39-pillow = 7.1.1-1.fc33
python3-PIL = 1.1.6-100
python-PIL = 1.1.6-100
python39-PIL = 1.1.6-100
Dummy when used with package name:
%package -n python3-pip
%python_provides python3-pip
Provides:
python3-pip = 20.0.2-1.fc33
python-pip = 20.0.2-1.fc33
python39-pip = 20.0.2-1.fc33
(all of them only once)
Any name is OK:
%python_provides wroom 666
Provides:
wroom = 666
What do you think?
Love it! I haven't thought about how feasible it is to implement, but I
trust you on that.
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