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Nixpkgs/Create and debug packages: Difference between revisions

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# At the top of the derivation, temporarily add <code>with import <nixpkgs> {};</code>. For now, don't worry too much about declaring every dependency as a parameter<!-- TODO clarify. "parameter of the default build function"? -->, to save time.
# At the top of the derivation, temporarily add <code>with import <nixpkgs> {};</code>. For now, don't worry too much about declaring every dependency as a parameter<!-- TODO clarify. "parameter of the default build function"? -->, to save time.
# Build the package with <code>nix-build</code>. Iterate on tweaking the derivation and rebuilding until it succeeds.
# Build the package with <code>nix-build</code>. Iterate on tweaking the derivation and rebuilding until it succeeds.
# For large projects with long compile times, you can use <code>nix-shell</code> instead to [https://ryantm.github.io/nixpkgs/stdenv/stdenv/#sec-building-stdenv-package-in-nix-shell run the individual phases].
# For large projects with long compile times, you can use <code>nix-shell</code> instead to [https://nixos.org/manual/nixpkgs/stable/#sec-building-stdenv-package-in-nix-shell run the individual phases].
# At this stage, you may encounter some build quirks of the project. Compile-time errors will hopefully explain what you're missing. For example [https://github.com/NixOS/nixpkgs/blob/643ce4bd0f057bc0b90f0faebeb83a3b14f01674/pkgs/tools/package-management/micromamba/default.nix#L6-L10 micromamba needs a specialized build of libsolv].
# At this stage, you may encounter some build quirks of the project. Compile-time errors will hopefully explain what you're missing. For example [https://github.com/NixOS/nixpkgs/blob/643ce4bd0f057bc0b90f0faebeb83a3b14f01674/pkgs/tools/package-management/micromamba/default.nix#L6-L10 micromamba needs a specialized build of libsolv].
# Read on below for further steps.
# Read on below for further steps.
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You would have seen the dependencies downloading, but the ''bc-build'' directory remains empty. The build system would next invoke a builder with some arguments. You can obtain the exact name of the builder (usually '''bash''') and the arguments '''args''' of the builder (typically a shell script) by checking the corresponding value in:
You would have seen the dependencies downloading, but the ''bc-build'' directory remains empty. The build system would next invoke a builder with some arguments. You can obtain the exact name of the builder (usually '''bash''') and the arguments '''args''' of the builder (typically a shell script) by checking the corresponding value in:
<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
$ nix show-derivation $(nix-instantiate .)
$ nix derivation show $(nix-instantiate .)
</syntaxhighlight>
</syntaxhighlight>


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<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
$ export out=~/tmpdev/bc-build/out
$ export out=~/tmpdev/bc-build/out
$ source $stdenv/setup
$ set -x # Optional: it prints all commands, can be practical to debug
$ set -x # Optional: it prints all commands, can be practical to debug
$ set +e # Optional: do not quit the shell on simple errors, Ctrl-C,...
$ set +e # Optional: do not quit the shell on simple errors, Ctrl-C,...
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</syntaxhighlight>
</syntaxhighlight>


To only run some specific phases:
To only run some specific phases, use runPhase:


<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
$ phases="buildPhase checkPhase" genericBuild
# Syntax: runPhase *phase*
$ runPhase unpackPhase
</syntaxhighlight>
</syntaxhighlight>


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Tip: A git repository can be used for snapshotting attempts at building the package. This also makes it easy to generate patches, should you need to.
Tip: A git repository can be used for snapshotting attempts at building the package. This also makes it easy to generate patches, should you need to.
== Adding custom libraries and dependencies to a package ==
If you are packaging a dependency, such as a library used by applications for them to compile their code, you might have found you'd like to test if the derivation file installs correctly and can be used by other software.
In order to do this, you'll need to make a simple program that references the library, make a derivation for this program, then add the dependency. For example:
Your program to test the library:
<syntaxhighlight lang="nix">
{
  pkgs ? import <nixpkgs> {
    overlays = [
      (final: prev: {
        my-library = prev.callPackage ./my-library.nix { };
      })
    ];
  },
}:
pkgs.callPackage (
  {
    stdenv,
    hello,
    pkg-config,
    my-library,
  }:
  stdenv.mkDerivation {
    pname = "something";
    version = "1";
    strictDeps = true;
    # host/target agnostic programs
    depsBuildBuild = [
      hello
    ];
    # compilers & linkers & dependecy finding programs
    nativeBuildInputs = [
      pkg-config
    ];
    # libraries
    buildInputs = [
      my-library
    ];
  }
) { }
</syntaxhighlight>


== nix channels ==
== nix channels ==
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</syntaxhighlight>
</syntaxhighlight>


== Formatting Packages with nixpkgs-fmt ==
== Formatting Packages with nixfmt ==
It is "good practice" to format packages in a way that following changed will create as minimal diffs as possible. The formatter [https://github.com/nix-community/nixpkgs-fmt nixpkgs-fmt] can be used for that.
It is "good practice" to format packages in a way that following changed will create as minimal diffs as possible. The formatter [https://github.com/NixOS/nixfmt nixfmt] can be used for that.
<syntaxhighlight lang="bash">
<syntaxhighlight lang="bash">
nixpkgs-fmt path/to/default.nix
nix-shell -p nixfmt-rfc-style --run 'nixfmt path/to/default.nix'
</syntaxhighlight>
</syntaxhighlight>


Retrieved from "https://wiki.nixos.org/wiki/Nixpkgs/Create_and_debug_packages"