When the build backend prints to stdout via non-Python means,
for example when a setup.py script calls a verbose program via os.system(),
the output leaked to stdout of %pyproject_buildrequires was treated as generated BuildRequires.
Fore example, if the setup.py script has:
rv = os.system('/usr/bin/patch -N -p3 -d build/lib < lib/py-lmdb/env-copy-txn.patch')
(From https://github.com/jnwatson/py-lmdb/blob/py-lmdb_1.0.0/setup.py#L117)
The stdout of /usr/bin/patch leaked to stdout of %pyproject_buildrequires:
[lmdb-1.0.0]$ /usr/bin/python3 -Bs /usr/lib/rpm/redhat/pyproject_buildrequires.py --python3_pkgversion 3 2>/dev/null
python3dist(setuptools) >= 40.8
python3dist(wheel)
patching file lmdb.h
patching file mdb.c
python3dist(wheel)
patching file lmdb.h
patching file mdb.c
This resulted in DNF errors like this:
No matching package to install: 'lmdb.h'
No matching package to install: 'mdb.c'
No matching package to install: 'patching'
Moreover, it resulted in bogus BuildRequires that may have existed (e.g. "file").
By replacing the usage of contextlib.redirect_stdout
(which only redirects Python's sys.stdout)
with a custom context manager that captures stdout on file descriptor level
(in addition to Python's sys.stdout),
we avoid this leak.
File descriptor magic heavily inspired by the capfd pytest fixture.
Related: rhbz#2168193
Before:
usage: %pyproject_buildrequires [-w] [-R] [-e TOXENVS] [-t] [-x EXTRAS] [-N] [REQUIREMENTS.TXT ...]
After:
usage: %pyproject_buildrequires [-x EXTRAS] [-t] [-e TOXENVS] [-w] [-R] [-N] [REQUIREMENTS.TXT ...]
The order was determined as:
0. suppressed options
1. extras, the easiest way to specify test deps (x)
2. tox related options (te)
3. build wheel, as it is provisional (w)
4. "disablers" (RN)
5. varargs are always listed last
Previous order was pretty much random.
Related: rhbz#2168193
The hook is optional, see https://www.python.org/dev/peps/pep-0517/#prepare-metadata-for-build-wheel
> If a build frontend needs this information and the method is not defined,
> it should call build_wheel and look at the resulting metadata directly.
This is not yet automatically detected because the feature is provisional.
Use `%pyproject_buildrequires -w` to opt-in.
Resolves: rhbz#2060109
%pyproject_buildrequires macro now accepts multiple file names to load
additional dependencies from them.
New option -N was added to disable automatical generation of requirements
in case package does not use build system. Option -N cannot be used in
combination with options -r, -e, -t, -x.
Co-authored-by: Miro Hrončok <miro@hroncok.cz>
Related: rhbz#1950291
