Dependency install order is 'broken'

[MMeent]

• Pip version: 8.1.2
• Python version: 3.5
• Operating System: Windows, Linux (Debian, Ubuntu)

Description:

For our Django project we have a few dependencies which we want to install using PIP. Most dependencies work normally on both operating systems, but not all.

Specifically I'm speaking about the rcssmin and rjsmin modules, which are required by the 'django-compressor'-library. These do not install normally on windows, but using --install-option="--without-c-extensions" made those two install just fine. Including this into the head of our windows requirements file does not make PIP use these flags while installing these modules. This means that we have to run the pip requirements command 2 times instead of one, which is not terrible but annoying.

Something that would fix this annoyance is that in the requirements file your -r <filename> includes are evaluated only after the other requirements in that file, or (an optional flag for) that requirements are installed in the order the file specifies.

What I've run:

~>pip --version
pip 8.1.2 from C:\Python35\lib\site-packages (python 3.5)

~>cat requirements-windows.txt
## first install rcssmin and rjsmin without c extensions to ensure it won't fail
rcssmin==1.0.6 --install-option="--without-c-extensions"
rjsmin==1.0.12 --install-option="--without-c-extensions"

~>cat requirements.txt
## Django 1.9+ and utils
Django>=1.9
docutils>=0.12
django-auth-ldap>=1.2.7

## django-compressor for sass compiling and ES6 compiling
django-compressor>=2.0
django-compressor-toolkit==0.5.0

[piotr-dobrogost]

All packages are being installed in topological order – see issue #2478 – and that's how it should be.
According to Per-requirement Overrides passing --install-option is supported so it should work...
Btw, the list of supported options in Requirements File Format section does not include --install-option nor --global-option mentioned in the Per-requirement Overrides section.

[MMeent]

The --install-option="without-c-flags" option works in a requirements file with pip install -r, so the problem is just that we cannot say "install this package before the others (with these options)".

Installing packages manually makes this possible, so why not allow an automated way?

If I cannot set the order of installation, can you please update the docs on requirements file from "list of items to be installed" to "set of requirements to be installed in topological, then undetermined order"? This would clear up the misunderstanding that the order of input makes a difference (list implies order implies control of order, which it doesn't have). Although the docs to warn about this not being true, the correct word for something makes a difference.

[dstufft]

We don't promise anything about what order packages are installed (or built) in. They might even be built in parallel at some point in the future. I'm fine if someone wants to submit a PR to change "list" to "set" but I wouldn't want to document what the current order is (because it can change at any time).

[piotr-dobrogost]

@MMeent
Your use of specific requirement file for Windows is a workaround and the real issue is not the fact you can't define the order of installation but that these two packages (rcssmin, rjsmin) do not have their dependencies fully specified. The tricky part here is that dependencies here mean different setuptools option passed which is rather seldom situation I guess. The question is if there is any way to pass different setuptools options based on platform?

[xavfernandez]

Like Donald said, pip install order should not be relevant.
I'm closing this.