urbit/nix/lib/dimension.nix

# From https://github.com/input-output-hk/plutus/blob/99f3a16cdf20e9e78a6105a097956a3773466b14/nix/dimension.nix
{
  /* dimension: name -> attrs -> function -> attrs
     where
       function: keyText -> value -> attrsOf package

     WARNING: Attribute names must not contain periods (".").
              See https://github.com/NixOS/nix/issues/3088

     NOTE: The dimension name will be picked up by agent and web ui soon.

     Specifies a dimension of the build matrix. For example

         dimension "Example" {
           withP = { p = true; }
           withoutP = { p = false; }
         } (key:      # either "withP" or "withoutP"
           { p }:     # either p = true or p = false
           myProject p
         )

     evaluates roughly to

         {
           withP = myProject true;
           withoutP = myProject false;
         }

     Use nested calls for multiple dimensions.

     Example:

         dimension "System" {
           "x86_64-linux" = {};
           # ...
           }: (system: {}:

           dimension "Nixpkgs release" (
             {
               "nixpkgs-19_03".nixpkgs = someSource
             } // optionalAttrs (system != "...") {
               "nixpkgs-unstable".nixpkgs = someOtherSource
             }
             ) (_key: { nixpkgs }:

             myProject system nixpkgs

           )
         )

     evaluates roughly to

         {
           x86_64-linux.nixpkgs-19_03 = myProject "x86_64-linux" someSource;
           x86_64-linux.nixpkgs-unstable = myProject "x86_64-linux" someOtherSource;
           ...
         }

     If you need to make references across attributes, you can do so by binding
     the result. Wherever you write

         dimension "My dimension" {} (key: value: f1 key value)

     You can also write

         let
           myDimension = dimension "My dimension" {} (key: value: f2 key value myDimension)
         in
           myDimension

     This example builds a single test runner to reuse across releases:

         let
           overlay =
             testRunnerPkgs: self: super: {
               # ...
             };
           myProject =
             { nixpkgs,
               pkgs ? import nixpkgs { overlays = [ overlay ]; },
               testRunnerPkgs ? pkgs
             }: pkgs;
         in

         let
           latest = "nixpkgs-19_03";
           releases =
             dimension "Nixpkgs release"
               {
                 nixpkgs-18_09.nixpkgs = someSource
                 nixpkgs-19_03.nixpkgs = someOtherSource
               }
               (_key: { nixpkgs }:

                 myProject {
                   inherit nixpkgs;
                   testRunnerPkgs = releases."${latest}";
                 }

               );
         in releases;
  */
  dimension = name: attrs: f:
    builtins.mapAttrs (k: v:
      let o = f k v;
      in o // { recurseForDerivations = o.recurseForDerivations or true; })
    attrs // {
      meta.dimension.name = name;
    };
}