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Comment by laserlight | Hacker News Reader

By documentation, I believe people mean tutorials. At least, lack of tutorials is my complaint. I've read all introductory material. I want to build a customized version of emacs on nix, yet I have no idea how to do it or where to start.

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Why use a tutorial when ChatGPT has you covered?

> How do I create a nix package that clones eMacs from GitHub and builds it from source?

{ pkgs ? import <nixpkgs> {}, fetchFromGitHub }:

let

  emacsSrc = fetchFromGitHub {

    owner = "emacs-mirror";

    repo = "emacs";

    rev = "master";

    sha256 = "0xabcd1234";

  };

in pkgs.stdenv.mkDerivation {

  name = "emacs";

  version = "27.1";

  src = emacsSrc;

  buildInputs = [ pkgs.autoconf pkgs.make ];

  configurePhase = ''

    autoconf

    ./configure --prefix=$out

  '';

  buildPhase = "make";

  installPhase = "make install";

}

As usual for ChatGPT this is full of mistakes and bad code. The buildPhase and installPhase it writes are completely unnecessary and worse than the default, the configurePhase might work in some cases but most likely won't, and it's unnecessary when instead autoreconfHook should be used, stdenv/autoconf should be taken as an argument for the function returning the derivation, autoconf should be a nativeBuildInput, make is already in stdenv, etc.

More fundamentally, even if the code produced by ChatGPT worked and was high-quality, why should a new user have to rely on a chatbot instead of useful/up-to-date tutorials and guides?

You're also supposed to call the pre and post hooks for these phases.

> sha256 = "0xabcd1234";

Am I right in assuming this is a ChatGPT misunderstanding, or is it a wildcard SHA256 in nix to allow any download?

Definitely not a wildcard, such things are not allowed. You can fetch at evaluation time with the built-in fetchers (builtins.fetchgit, builtins.fetchTarball, etc) and not provide a hash, which makes the expression "impure", which means the expression wouldn't be acceptable in nixpkgs and it has consequences for flakes.

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