pip-compile --no-header <blank requirements.in> neither creates nor overwrites requirements.txt

[AndydeCleyre]

If requirements.in is empty, running pip-compile will create or clobber requirements.txt, thereby removing all requirements, but if --no-header is passed to pip-compile, requirements.txt will not be affected in any way, no matter its state.

Environment Versions

1. Linux
2. Python version: 3.7.4
3. pip version: 19.2.3
4. pip-tools version: 4.1.0

Steps to replicate

touch requirements.in
pip-compile --no-header
# no txt file created (unexpected)
pip-compile
# txt file created (as expected)
echo plumbum > requirements.in
pip-compile
echo > requirements.in
pip-compile --no-header
cat requirements.txt

full, unexpected:

#
# This file is autogenerated by pip-compile
# To update, run:
#
#    pip-compile
#
plumbum==1.6.7

[atugushev]

Hello @AndydeCleyre,

Thanks for the report! That's a good catch!

[AndydeCleyre]

I'll submit a pull request for this today. Would it be preferable for the writer line iterator to simply always yield a final extra newline, or to actually keep track of whether or not it has yielded any real lines along the way, and only add the newline in that case?

@atugushev

[atugushev]

@AndydeCleyre

I'd prefer this suggestion:

keep track of whether or not it has yielded any real lines along the way, and only add the newline in that case?