Installation with --pure doesn't seem to work any more

[aplaice]

It seems that the method of installing without C bindings recommended in the README doesn't work.

To reproduce

Clone from master and run:

python3 setup.py --pure install

(Or alternatively run pip3 install dulwich --global-option="--pure".)

Expected behaviour

Dulwich is set up without the C extensions.

Actual behaviour

The following error message is raised:

usage: setup.py [global_opts] cmd1 [cmd1_opts] [cmd2 [cmd2_opts] ...]
   or: setup.py --help [cmd1 cmd2 ...]
   or: setup.py --help-commands
   or: setup.py cmd --help

error: option --pure not recognized

Speculation

I suspect that the commit 3b22cba273693e20c491de48cfdcbc30ab0c517d caused the change in behaviour, but haven't investigated further.

Context

I use the "pure" version of Dulwich for an add-on for Anki (CrowdAnki), which has to be distributable in the same form for all platforms, and hence can't rely on compiled C code. This worked with previous versions of Dulwich (e.g. 0.20.24), but doesn't work with the latest version.

---

Thanks for the extremely useful package!

[aplaice]

Thanks so much for the fast fix! (setupy.py with --pure does indeed work now!)

[jelmer]

No worries, thanks for the report.

Ideally setuptools would add some functionality than does this..

[aplaice]

Sorry to bother you again, for something that's totally not your fault (but is due to the changes in pip and setuptools), but unfortunately, it's still the case that neither pip install dulwich --global-option="--pure" nor pip install --no-binary dulwich -r <(echo 'dulwich --global-option="--pure"') (i.e. using requirements.txt) works to get a pure-python install (with or without --no-binary) (--install-option etc. also doesn't work).

(Tested with pip 22.3.1.)

python setup.py install --pure and python setup.py bdist_wheel --pure both function as expected.

Unfortunately, with PEP517 (I think), setuptools/pip do not pass the "--global-option" (when it's passed in this way) to setup.py. (setup.py is, however, still being called, to obtain the ext_modules.)

After some investigations, it seems that (either of) the two following monstrosities do work (producing a pure-python install):

pip install --no-binary dulwich dulwich --config-settings "--global-option=--pure"

pip install --no-binary dulwich dulwich --config-settings "--build-option=--pure"

(--no-binary is needed to avoid using the wheels from PyPi which logically do contain the built C bindings.)

However, (while I'll probably be using one of them for my use (in CrowdAnki)), I'm not sure if they're the correct approach (there might be something less verbose). It also seems that --config-settings cannot (yet) be specified in requirements.txt (pypa/pip#11325). Hence, I'm not opening a PR to update the docs.

(Sorry for not having tested this at the time, but I had assumed that if setup.py worked then so would pip.)

[jelmer]

Unfortunately the pip ecosystem is out of Dulwich' control :) I'm happy to take a PR that updates the instructions for pip.

I'm also somewhat leaning towards just drop those instructions, rather than trying to chase pip and come up with workarounds. Ideally this would be fixed with a flag in upstream pip to indicate you prefer pure packages.