Option --pre doesn't work in requirements.in

[atugushev]

The option --pre set in requirements.in doesn't work as expected. Neither --pre package or package==0.0.1 --pre. If --pre passed to the CLI it works like a charm. It seems PyPIRepository doesn't respect PackageFinder.allow_all_prereleases parameter.

Environment Versions

1. OS Type MacOS 10.14.3
2. Python version: 3.7.3
3. pip version: pip 19.1.1 from /Projects/pip-tools/.venv/lib/python3.7/site-packages/pip (python 3.7)
4. pip-tools version: pip-compile, version 3.7.0

Steps to replicate

1. requirements.in:

cat << EOF > requirements.in
--pre django
django<2.2rc1 --pre
EOF

2. pip-compile -rqo-

Expected result

#
# This file is autogenerated by pip-compile
# To update, run:
#
#    pip-compile --output-file=-
#
django==2.2b1
pytz==2019.1              # via django
sqlparse==0.3.0           # via django

Actual result

#
# This file is autogenerated by pip-compile
# To update, run:
#
#    pip-compile --output-file=-
#
django==2.1.8
pytz==2019.1              # via django

Works fine with

$ pip-compile -rqo- --pre
#
# This file is autogenerated by pip-compile
# To update, run:
#
#    pip-compile --output-file=- --pre
#
django==2.2b1
pytz==2019.1              # via django
sqlparse==0.3.0           # via django

[atugushev]

@blueyed

digging in pip internals i've found that --pre is a global boolean flag. You can't set --pre to a specific package, neither in CLI or requirements.txt file, see:

$ pip install --pre=django django channels

Usage:
  pip install [options] <requirement specifier> [package-index-options] ...
  pip install [options] -r <requirements file> [package-index-options] ...
  pip install [options] [-e] <vcs project url> ...
  pip install [options] [-e] <local project path> ...
  pip install [options] <archive url/path> ...

--pre option does not take a value

So --pre can be used only in two ways:

1. As CLI option: pip install --pre
2. As file-based option inside requirements.txt:

$ cat requirements.txt
--pre
django

Looks like it's not a bug, but in the meantime maybe it's a reason to raise an issue on pip side for these points:

• if there is a --pre django in requirements.txt, pip should set --pre and install django
• if there is a django --pre in requirements.txt, pip should raise "unsupported requirement option"

Cheers!

[atugushev]

Anyways, --pre in requirements.in file doesn't work.