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0 pointstakeda6y ago0 comments

That's the cost of full reproducibility though. If Nix would not expect the postgresql package listed in dependencies and instead relied on what's currently installed on your system we would get to the starting point. Where something works on one person's computer but doesn't on another.

Yes it is harder, but if you incorporate nix definitions in your source code (you need to pin nixpkgs though) then everyone will get exact same versions of the packages and your code works on everyone's computer.

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throwaway8943456y ago

There are other ways to get enough reproducibility without the headaches of Nix, however, so that’s what we ended up doing. Reproducibility is nice, but if we need to be able to develop software quickly and for the time being, Nix is an impediment. As previously mentioned, this doesn’t have to be the case; it’s mostly an artifact of lack of documentation and a strong preference for the novel and unfamiliar over the familiar, but also for lack of escape hatches.

takedaOP6y ago

What other ways?

If you don't specify essential dependency and rely on the dependency to be installed that by definition is not reproducible.

The fix in Nix for psycopg2 is specify that it also depends on postgresql, and that's all what's needed.

Here's definition of psycopg2 from NixPkgs: https://github.com/NixOS/nixpkgs/blob/master/pkgs/developmen... (the highlighted part is the only thing that's needed everything else is just informational, doCheck is to control whether unit tests should be run during build and disabled = isPyPy tells that psycopg2 doesn't work with PyPy, which it doesn't work with, because PyPy doesn't support C extensions)

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