stdenv: make meta.position overridable

[lolbinarycat]

this is done simply by changing the order in which attrsets are merged with //

fixes #295907

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)
  • sandbox = relaxed
  • sandbox = true
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 24.05 Release Notes (or backporting 23.05 and 23.11 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

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[piegamesde]

I can't judge for the validity of the motivation for this change, but at least there should be a comment about in the code, since this is a very subtle thing which may regress on the next refactoring. If there is the possibility of adding regression tests, that would be even better.

[lolbinarycat]

i feel like if this needs a comment, then so would almost every use of //. i'll add a test.

[lolbinarycat]

@piegamesde thanks for the review btw, is there any chance you could give #294347 a glance too?

[piegamesde]

Sorry my capacities are mostly bound elsewhere currently

[lolbinarycat]

ok, thanks anyways

[philiptaron]

Yeah, checks out.

[drupol]

Diff LGTM

[Aleksanaa]

Yes this makes sense. But maybe it would be better to let someone who knows better judge it.

[Aleksanaa]

To not let us in a dumb situation like last time (although seemingly not)

[philiptaron]

I think it's pretty self-explanatory; the only sticky situation would be if things further in the // block would prevent overrides... but they should prevent overrides actually.

This bit:

{
  # Expose the result of the checks for everyone to see.
  inherit (validity)
    unfree
    broken
    unsupported
    insecure
    ;

  available =
    validity.valid != "no"
    && (
      if config.checkMetaRecursively or false then all (d: d.meta.available or true) references else true
    );
}

[eclairevoyant]

What do you mean by "should prevent overrides" here? or rather why?

[philiptaron]

What do you mean by "should prevent overrides" here? or rather why?

The five fields that are made consistent in this function are unfree, broken, unsupported, insecure, and available. Earlier in this file, the checkValidity function did work to turn the args.meta values into consistent fields. So if we were to place //args.meta after the block I cited, the meta values would be inconsistent.

Imagine a derivation with meta.insecure = "lol". We want the actual insecurity check that was performed above, not that value.

As I understand it, anyway.

[pbsds]

my diff in the related effort #329900 (comment) might be of interest, it should apply here as well

[philiptaron]

I'd like to merge this. Mind fixing the merge conflict?

[pbsds]

from my related pr:

I can find both good and bad cases in the diff, i reckon most of the bad ones come from inherit (some-package) meta; which now becomes a major foot-gun

As such i'd like an entry into the release notes and some documentation covering this foot-gun

[philiptaron]

@pbsds: in the diff you cited, are the following examples of "bad"?

-python311Packages.certbot-dns-ovh: ./pkgs/development/python-modules/certbot-dns-ovh/default.nix:37
-python311Packages.certbot-dns-rfc2136: ./pkgs/development/python-modules/certbot-dns-rfc2136/default.nix:35
-python311Packages.certbot-dns-route53: ./pkgs/development/python-modules/certbot-dns-route53/default.nix:35
+python311Packages.certbot-dns-ovh: ./pkgs/development/python-modules/certbot/default.nix:90
+python311Packages.certbot-dns-rfc2136: ./pkgs/development/python-modules/certbot/default.nix:90
+python311Packages.certbot-dns-route53: ./pkgs/development/python-modules/certbot/default.nix:90

-ocamlPackages.json-data-encoding-bson: ./pkgs/development/ocaml-modules/json-data-encoding/bson.nix:19
+ocamlPackages.json-data-encoding-bson: ./pkgs/development/ocaml-modules/json-data-encoding/default.nix:21

-steam-run: ./pkgs/games/steam/fhsenv.nix:344
-steam-run-native: ./pkgs/games/steam/fhsenv.nix:344
-steam-small: ./pkgs/games/steam/fhsenv.nix:313
+steam-run: ./pkgs/games/steam/steam.nix:43
+steam-run-native: ./pkgs/games/steam/steam.nix:43
+steam-small: ./pkgs/games/steam/steam.nix:43

And the following examples of "good"?

-vimPlugins.nvim-treesitter-parsers.yaml: ./pkgs/applications/editors/vim/plugins/vim-utils.nix:418
-vimPlugins.nvim-treesitter-parsers.yang: ./pkgs/applications/editors/vim/plugins/vim-utils.nix:418
-vimPlugins.nvim-treesitter-parsers.yuck: ./pkgs/applications/editors/vim/plugins/vim-utils.nix:418
-vimPlugins.nvim-treesitter-parsers.zathurarc: ./pkgs/applications/editors/vim/plugins/vim-utils.nix:418
-vimPlugins.nvim-treesitter-parsers.zig: ./pkgs/applications/editors/vim/plugins/vim-utils.nix:418
+vimPlugins.nvim-treesitter-parsers.yaml: ./pkgs/applications/editors/vim/plugins/nvim-treesitter/generated.nix:3139
+vimPlugins.nvim-treesitter-parsers.yang: ./pkgs/applications/editors/vim/plugins/nvim-treesitter/generated.nix:3150
+vimPlugins.nvim-treesitter-parsers.yuck: ./pkgs/applications/editors/vim/plugins/nvim-treesitter/generated.nix:3161
+vimPlugins.nvim-treesitter-parsers.zathurarc: ./pkgs/applications/editors/vim/plugins/nvim-treesitter/generated.nix:3172
+vimPlugins.nvim-treesitter-parsers.zig: ./pkgs/applications/editors/vim/plugins/nvim-treesitter/generated.nix:3183

And the following an example of "meh"?

-xaos: ./pkgs/applications/graphics/xaos/default.nix:44
+xaos: ./pkgs/applications/graphics/xaos/default.nix:12

[pbsds]

correct

[lolbinarycat]

I'd like to merge this. Mind fixing the merge conflict?

I no longer work on nixpkgs, I deleted my local clone, and my internet connection is prohibitively slow.

Sorry, but I'm gonna have to pass this along to someone else.

[wolfgangwalther]

Superseded by #359191