Changes/Platform Python Stack

Platform Python Stack

Summary

A revisit of the System Python change from Fedora 24. It has been renamed from System Python to Platform Python not to collide with upstream PEP 432.

Platform Python will be a separate stack fo Python packages living in the Platform module aimed to provide all necessary dependencies to run and build dnf. In Fedora 27 this will be Python 3.6 (same version as python3, but this might change in the future with the Modularity effort).

Owner

• Name: Miro Hrončok
• Email: <python-maint at redhat.com>
• Release notes owner:

Current status

• Targeted release: Fedora 27
• Last updated: 2017-07-04
• Tracker bug: <will be assigned by the Wrangler>

Detailed Description

The changes made during the System Python change from Fedora 24 will be reverted.

A new platform-python (source) package will be created as a copy of the python3 package. It will only be built as part of the Platform module. Unlike python3, it will be changed so that:

• the location of files will not be /usr/lib/python3.6/ but /usr/lib/platform-python/
  • the script that generates the python(abi) requirement will be adapted to generate platform-python(abi) requirement for that location
• the location of the binary will be /usr/libexec/platform-python
• all subpackages will be named platform-python-*
• the debug build will be disabled
• the modules that are (before this change) not part of system-python-libs but rather python3-libs will relocate to platform-python-libs-devel to be available only on build-time
• platform-python-libs will provide platform-python(abi) instead of python(abi)

Several packages (see bellow) will be adapted to build a new platform-python- subpackage when built for the platform module. Example specfile of such package:

%global pypi_name foo

Name:           python-%{pypi_name}
Version:        0.13
Release:        1%{?dist}
Summary:        Python %{pypi_name} module

License:        GPLv2
URL:            https://github.com/fedora-python/%{pypi_name}
Source0:        https://files.pythonhosted.org/packages/source/f/%{pypi_name}/%{pypi_name}-%{version}.tar.gz


%if 0%{?platform_module}
  %global pyprefix platform-python
%else
  %global pyprefix python3
  %global platform_module 0
%endif

%if !%{platform_module}
BuildRequires:  python2-devel
BuildRequires:  python2-setuptools
%endif

BuildRequires:  %{pyprefix}-devel
BuildRequires:  %{pyprefix}-setuptools


BuildArch:      noarch

%description
...

%if !%{platform_module}
%package -n     python2-%{pypi_name}
Summary:        %{summary}
Requires:       python2-bar
%{?python_provide:%python_provide python2-%{pypi_name}}

%description -n python2-%{pypi_name}
...
%endif

%package -n     %{pyprefix}-%{pypi_name}
Summary:        %{summary}
Requires:       %{pyprefix}-bar
%{?python_provide:%python_provide %{pyprefix}-%{pypi_name}}

%description -n %{pyprefix}-%{pypi_name}
...



%prep
%autosetup -n %{pypi_name}-%{version}


%build
%if !%{platform_module}
%py2_build
%endif
%py3_build

%install
%if !%{platform_module}
%py2_install
rm %{buildroot}%{_bindir}/%{pypi_name}
%endif

%py3_install


%check
%if !%{platform_module}
export PYTHONPATH=%{buildroot}%{python2_sitelib}
%{__python2} -m unittest discover -v
%endif

export PYTHONPATH=%{buildroot}%{python3_sitelib}
%{__python3} -m unittest discover -v


%if !%{platform_module}
%files -n python2-%{pypi_name}
%doc README.rst CHANGES.rst
%license COPYING
%{python2_sitelib}/%{pypi_name}.so
%{python2_sitelib}/%{pypi_name}-%{version}-py?.?.egg-info
%endif

%files -n %{pyprefix}-%{pypi_name}
%doc README.rst CHANGES.rst
%license COPYING

%if %{platform_module}
  %exclude %{_bindir}/%{pypi_name}
%else
  %{_bindir}/%{pypi_name}
%endif

%{python3_sitelib}/%{pypi_name}.cpython-%{python3_version_nodots}*.so
%{python3_sitelib}/%{pypi_name}-%{version}-py?.?.egg-info


%changelog
...

The complete list of affected packages is not final yet. It should be all the Python build dependencies of dnf and their build dependencies as well, excluding packages only needed to build the documentation (because the docs package can be pulled form the standard build).

Currently, we have established this as a list of packages:

dbus-python
gpgme
libcomps
libdnf
librepo
pytest
python-argcomplete
python-cffi
python-contextlib2
python-coverage
python-cryptography
python-decorator
python-extras
python-fixtures
python-funcsigs
python-hypothesis
python-idna
python-iniparse
python-jinja2
python-jsonschema
python-keyring
python-linecache2
python-markupsafe
python-mimeparse
python-mock
python-nose
python-pbr
python-pexpect
python-pip
python-ply
python-ptyprocess
python-py
python-pyasn1
python-pycparser
python-pygpgme
python-pytest-timeout
python-rpm-macros
python-SecretStorage
python-setuptools
python-setuptools_scm
python-six
python-testtools
python-traceback2
python-unittest2
python-wheel
pyxattr
pyxdg
rpm

Only the following list will be installable from the platform module (the rest is merely meant as a build dependency):

platform-python
platform-python-dnf
platform-python-gpg
platform-python-hawkey
platform-python-iniparse
platform-python-libcomps
platform-python-librepo
platform-python-libs
platform-python-rpm
platform-python-six

Benefit to Fedora

With the Modularity effort a minimal stack of Python only needed to run dnf is needed to be part of the Platform.

Scope

• Proposal owners:
  • identify a list of runtime and build dependencies of dnf
  • create a platform-python source package
  • change the script that generates the python(abi) requirements to also generate platform-python(abi) requirements
  • revert system-python related things from the python3 package, add provides and obsoletes
  • change specfiles of identified packages to create platform-python- subpackages in platform module
  • switch dnf to use that stack

• Other developers: N/A (not a System Wide Change)

• Release engineering: #Releng issue number (a check of an impact with Release Engineering is needed)
  • List of deliverables: N/A (not a System Wide Change)

• Policies and guidelines: N/A (not a System Wide Change)

• Trademark approval: N/A (not needed for this Change)

Upgrade/compatibility impact

N/A (not a System Wide Change)

How To Test

N/A (not a System Wide Change)

User Experience

Nothing should change for the user, except a slightly larger amount of packages will be installed on the system.

Dependencies

N/A (not a System Wide Change)

Contingency Plan

• Contingency mechanism: (What to do? Who will do it?) N/A (not a System Wide Change)
• Contingency deadline: N/A (not a System Wide Change)
• Blocks release? No (not a System Wide Change)
• Blocks product? No

If not done on time: Keep dnf running on python3. Finish the work in time of Fedora 28.

If proven not to work as designed: Retire platform-python package and remove all changes in said packages.

Documentation

N/A (not a System Wide Change)