# 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; }; }