treewide: remove placeholder usage

[jtojnar]

Motivation for this change

I keep forgetting 17.03 is not released yet, see 2abac54

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option build-use-sandbox in nix.conf on non-NixOS)
• 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 nox --run "nox-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Fits CONTRIBUTING.md.

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[matthewbauer]

@jtojnar Can this be merged? Lots of people have been complaining about some variation of this.

Can probably end up closing #37875 with this.

[jtojnar]

I did not yet have time to test if it works (webkitgtk rebuild).

[matthewbauer]

IMO we should just merge this immediately and test it through Hydra. The placeholder usage means that evaluation is broken for Nix 1.11 users which is pretty critical (and means they can't upgrade even if they want to).

[jtojnar]

Apparently, at least libgee was broken by this.

[jtojnar]

Okay, all the packages seem to build and the executables run.

[infinisil]

You forgot https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/libraries/pipewire/default.nix#L37

[jtojnar]

@infinisil does it matter? It is only used by mutter. Who would be using unstable desktop but outdated Nix?

[LnL7]

Yes, it matters for evaluation.

[infinisil]

@jtojnar nixpkgs is used by many people that aren't using NixOS, and they should be able to use mutter and pipewire too (without having to update to latest Nix). Nix and nixpkgs should mostly stay forwards and backwards compatible

[jtojnar]

Is not evaluation lazy? Anyway, this broke evolution-data-server, will push a fix for both shortly.

[matthewbauer]

Yeah evaluation is lazy if you are using nix-env -iA. Unfortunately lots of people are still in the habit of using nix-env -i. Since it's still supported we aim to not break evaluation (although this is a special case because it will evaluate under Nix 2.0 which OfBorg and Hydra are on).

[jtojnar]

Fix pushed, including the one for #36978: 025881c

[matthewbauer]

Awesome thanks!