php.packages: Make packages overridable

[jtojnar]

Motivation for this change

This will allow patching extensions without having to manually having to patch all occurrences in the dependency tree (like I did in fossar/selfoss@cb22131), see clean-up PR depending on this PR.

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS linux)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Ensured that relevant documentation is up to date
• Fits CONTRIBUTING.md.

[aanderse]

Unfortunately, Nixpkgs repository does not contain old PHP versions
but it is trivial with Nix to build them ourselves. We will be able to
use Cachix to avoid rebuilding them over and over again.

It sounds like you're going to publish this for broad use? I have a few internal applications I need to support still running 5.6 and this would be really nice... Would you mind sending me a ping when this is available?

[jtojnar]

@aanderse It is already in the selfoss repository (see the links in the OP). Though I hope to remove PHP 5.6 as soon as I manage to release selfoss 2.19, which is the last version I promised PHP 5 support for.

[aanderse]

@jtojnar there isn't a binary cache yet, though, is there? Thanks! Awesome work.

[jtojnar]

@aanderse Yes, there is. Turns out Cachix is amazing: cachix use fossar

[FRidh]

Related PR for emacs #107152. We really need to converge on a single interface here (partially NixOS/rfcs#67).

[FRidh]

Python nowadays also supports overrideScope' but it has not been documented yet. My intention is to deprecate this packageOverrides because it does not compose.

[jtojnar]

It does actually compose:

let
  pkgs = import ./. { };

  idOverlay = final: prev: {};
  composeOverlays =
    old:
    new:

    final:
    prev:

    let
      oldInstantiated = old final prev;
      prevWithOld = prev // oldInstantiated;
    in
      oldInstantiated // new final prevWithOld;

  oldPhp = pkgs.php.override {
    packageOverrides = final: prev: {
      extensions = prev.extensions // {
        mysqlnd = prev.extensions.mysqlnd.overrideAttrs (attrs: {
          foo = "foo";
        });
      };
    };
  };
in
  oldPhp.override (oldOverrides: {
    packageOverrides = composeOverlays (oldOverrides.packageOverrides or idOverlay) (final: prev: {
      extensions = prev.extensions // {
        mysqlnd = prev.extensions.mysqlnd.overrideAttrs (attrs: {
          foo = prev.extensions.mysqlnd.foo or "" + "bar";
        });
      };
    });
  })

But yeah, it is a mouthful.

[FRidh]

Wrote a draft for an RFC on this topic NixOS/rfcs#83.

[jtojnar]

Merging as is for now, will update it to match the RFC once we figure it out.

[etu]

I approve of these changes since it doesn't make sense to wait around for the RFC process to happen. This brings us benefits right now, and we can match the RFC API later on.

[jtojnar]

@aanderse I have extracted the PHP expressions into a separate repository: https://github.com/fossar/nix-phps

[aanderse]

@jtojnar thank you very much! That is great! ✨

[nixos-discourse]

This pull request has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/php-extensions-not-building-against-php-with-overridden-attributes/11451/2