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by berti 2255 days ago
Read your way down this thread and note that every defence of Nix is merely shifting the blame in it's entirety to some other part of the ecosystem. Rightly or wrongly that's a big problem for Nix if it intends to gain widespread acceptance.
2 comments
takeda 2255 days ago
It's true somewhat though, but it's a problem is not easy to solve for Python.

The problem is that Python supports C extensions, and for example the psycopg2 package has an extra dependency on a libpq which it expects to have installed on the system i.e. if you were using a docker you would do something like yum install postgresql-devel otherwise it will fail. Python won't install it for you and it doesn't even have a way to relay (except for error message) that such package is needed.

Many people actually get stuck with this and won't know what to do, but quick google show that package is needed they install and everything works. Nix is functional and doesn't have state so you can't just invoke nix-env -i postgresql and now everything will start to work, that behavior would actually ruin reproducibility. Nix instead expects that the C dependency is also provided otherwise it will refuse the build.

That's what OP meant where he said Nix exposes weak build systems.

Anyway, there was significant progress in making things better in python, it is still not awesome, but it is very close. Actually the biggest pain point right now is to setup a build environment that's convenient to use.

I recently created a template that shows how to do it: https://github.com/takeda/example_python_project

It uses pip2nix and it can automatically figure out all python dependencies, the packages like psycopg2 need an additional entry like this: https://github.com/takeda/example_python_project/blob/master... because PyPI packages don't specify any system dependencies.

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Ericson2314 2255 days ago
Almost every language build system ecosystem does someting quite wrong---it's irked me for a while. I hope to within the next year or two find the time/budget to pick one language and make it work properly, and integrate with Nix perfectly.

I think not everything knows what they are missing, and by doing one complete demo we'll be able to raise the bar and give the other languages a good jolt.

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