lib.systems.doubles.all: reorganize

[alyssais]

Motivation for this change

The previous mess was partially grouped by OS, and partially grouped
by architecture, which made it very difficult to know where to add new
entries.

I've chosen to group by OS entirely, because OSes are likely to
maintain exhaustive lists of supported architectures, but it's far
less likely we'd be able to find exhaustive lists of supported OSes
for every architecture.

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.

[Ericson2314]

I'm fine with rearranging the big lists, but I think all lists below should be calculated not handwritten. This is important to ensure that the predicates and the platforms list stay in sync.

[Ericson2314]

See also https://github.com/NixOS/nixpkgs/blob/master/lib/tests/systems.nix for the lists which are supposed to stay hand coded.

[alyssais]

I'm fine with rearranging the big lists, but I think all lists below should be calculated not handwritten. This is important to ensure that the predicates and the platforms list stay in sync.

I don't understand what you mean by this. Can you rephrase?

[Ericson2314]

I mean when we do e.g.

darwin = filterDoubles predicates.isDarwin;

and then in https://github.com/NixOS/nixpkgs/blob/master/lib/tests/systems.nix do

testdarwin = mseteq darwin [ "x86_64-darwin" "i686-darwin" "aarch64-darwin" "armv7a-darwin" ];

we are testing isDarwin does what we expect, but if we write

darwin = [ "x86_64-darwin" "i686-darwin" "aarch64-darwin" "armv7a-darwin" ];

here we are no longer testing isDarwin.

[alyssais]

I mean when we do e.g. ``` darwin = filterDoubles predicates.isDarwin; ``` and then in https://github.com/NixOS/nixpkgs/blob/master/lib/tests/systems.nix do ``` testdarwin = mseteq darwin [ "x86_64-darwin" "i686-darwin" "aarch64-darwin" "armv7a-darwin" ]; ``` we are testing `isDarwin` does what we expect, but if we write ``` darwin = [ "x86_64-darwin" "i686-darwin" "aarch64-darwin" "armv7a-darwin" ]; ``` here we are no longer testing `isDarwin`.

Ah, I see. So should I just make `all` a big array, with comments to seperate different OSes maybe, and go back to generating all the smaller lists?

[Ericson2314]

That sounds great to me!