Remove flake utils (#2027)

* Remove flake-utils

* WIP

* Try to depend on pkgs rather than system

* Use builtins

* Try putting back internal as it was

* Remove/update some comments

* Better name for forEachSystem'

* Minor changes

* Remove extra nixpkgs in default.nix

* Use flake-compat override-inputs to implement sourcesOverride

This makes the overlays in compat internal the same as the ones in the
flake.

* Deprecate using overlaysOverrideable

* Move internal.compat to default.nix

* Adapt ci.nix

* ghc945 -> ghc947

* Minor changes

* Slightly more readable

* Fix

* Bump haskell.nix in nix-tools flake.

This removes the transitive dependency on
https://github.com/hamishmack/flake-utils which is not needed anymore.

* Pre-fetch nixpkgs before calling flake-compat

* Fix evalSystem in ci.nix

* Avoid issues with restricted evaluation

* Trivial change

---------

Co-authored-by: Hamish Mackenzie <Hamish.K.Mackenzie@gmail.com>

Author: andreabedini

ci-lib.nix

@@ -1,8 +1,5 @@
-{
-  # Generic nixpkgs, use *only* for lib functions that are stable across versions
-  pkgs,
-  lib ? pkgs.lib
-}: rec {
+{ lib }:
+rec {
   inherit (import ./dimension.nix) dimension;
 
   # A filter for removing packages that aren't supported on the current platform

ci.nix

@@ -1,29 +1,49 @@
 # 'supportedSystems' restricts the set of systems that we will evaluate for. Useful when you're evaluating
 # on a machine with e.g. no way to build the Darwin IFDs you need!
 { ifdLevel ? 3
-# Whether or not we are evaluating in restricted mode. This is true in Hydra, but not in Hercules.
-, restrictEval ? false
 , checkMaterialization ? false
-, compat
-, system
+, system ? builtins.currentSystem
 , evalSystem ? builtins.currentSystem or "x86_64-linux"
-, pkgs ? (compat { inherit system; }).pkgs }:
+  # NOTE: we apply checkMaterialization when defining nixpkgsArgs
+, haskellNix ? import ./default.nix { inherit system ; }
+}:
  let
-  inherit (import ./ci-lib.nix { inherit pkgs; }) dimension platformFilterGeneric filterAttrsOnlyRecursive;
-  inherit (pkgs.haskell-nix) sources;
+  inherit (haskellNix) inputs;
+  inherit (inputs.nixpkgs) lib;
+  inherit
+    (import ./ci-lib.nix { inherit lib; })
+    dimension
+    platformFilterGeneric
+    filterAttrsOnlyRecursive;
+
+  # short names for nixpkgs versions
   nixpkgsVersions = {
-    "R2205" = "nixpkgs-2205";
-    "R2211" = "nixpkgs-2211";
-    "R2305" = "nixpkgs-2305";
-    "unstable" = "nixpkgs-unstable";
+    "R2205" = inputs.nixpkgs-2205;
+    "R2211" = inputs.nixpkgs-2211;
+    "R2305" = inputs.nixpkgs-2305;
+    "unstable" = inputs.nixpkgs-unstable;
   };
-  haskellNix = compat { inherit checkMaterialization system; };
-  nixpkgsArgs = haskellNix.nixpkgsArgs // {
+
+  nixpkgsArgs = {
+    # set checkMaterialization as per top-level argument
+    overlays = [
+      haskellNix.overlay
+      (final: prev: {
+        haskell-nix = prev.haskell-nix // {
+          inherit checkMaterialization;
+        };
+      })
+    ];
     # Needed for dwarf tests
-    config = haskellNix.nixpkgsArgs.config // {
-      permittedInsecurePackages = ["libdwarf-20210528" "libdwarf-20181024" "dwarfdump-20181024"];
+    config = haskellNix.config // {
+      permittedInsecurePackages = [
+        "libdwarf-20210528"
+        "libdwarf-20181024"
+        "dwarfdump-20181024"
+      ];
     };
   };
+
   compilerNixNames = nixpkgsName: nixpkgs:
     # Include only the GHC versions that are supported by haskell.nix
     nixpkgs.lib.filterAttrs (compiler-nix-name: _:
@@ -73,31 +93,30 @@
     # of 'lib.systems.examples' are not understood between all versions
     let lib = nixpkgs.lib;
     in lib.optionalAttrs (nixpkgsName == "unstable"
-      && ((system == "x86_64-linux"  && __elem compiler-nix-name ["ghc8107" "ghc962" "ghc9820230704"])
-       || (system == "aarch64-linux" && __elem compiler-nix-name ["ghc8107" "ghc962" "ghc9820230704"])
-       || (system == "x86_64-darwin" && __elem compiler-nix-name ["ghc8107" "ghc962" "ghc9820230704"])
-       || (system == "aarch64-darwin" && __elem compiler-nix-name ["ghc8107" "ghc962" "ghc9820230704"])
+      && ((system == "x86_64-linux"  && builtins.elem compiler-nix-name ["ghc8107" "ghc962" "ghc9820230704"])
+       || (system == "aarch64-linux" && builtins.elem compiler-nix-name ["ghc8107" "ghc962" "ghc9820230704"])
+       || (system == "x86_64-darwin" && builtins.elem compiler-nix-name ["ghc8107" "ghc962" "ghc9820230704"])
+       || (system == "aarch64-darwin" && builtins.elem compiler-nix-name ["ghc8107" "ghc962" "ghc9820230704"])
        )) {
     inherit (lib.systems.examples) ghcjs;
   } // lib.optionalAttrs (nixpkgsName == "unstable"
-      && ((system == "x86_64-linux"  && __elem compiler-nix-name ["ghc8107" "ghc902" "ghc926" "ghc927" "ghc928" "ghc947" "ghc962" "ghc9820230704"])
-       || (system == "x86_64-darwin" && __elem compiler-nix-name []))) { # TODO add ghc versions when we have more darwin build capacity
+      && ((system == "x86_64-linux"  && builtins.elem compiler-nix-name ["ghc8107" "ghc902" "ghc926" "ghc927" "ghc928" "ghc947" "ghc962" "ghc9820230704"])
+       || (system == "x86_64-darwin" && builtins.elem compiler-nix-name []))) { # TODO add ghc versions when we have more darwin build capacity
     inherit (lib.systems.examples) mingwW64;
-  } // lib.optionalAttrs (system == "x86_64-linux" && nixpkgsName == "unstable" && __elem compiler-nix-name ["ghc8107" "ghc902" "ghc922" "ghc923" "ghc924" "ghc926" "ghc927" "ghc928" "ghc947" "ghc962" "ghc9820230704"]) {
+  } // lib.optionalAttrs (system == "x86_64-linux" && nixpkgsName == "unstable" && builtins.elem compiler-nix-name ["ghc8107" "ghc902" "ghc922" "ghc923" "ghc924" "ghc926" "ghc927" "ghc928" "ghc947" "ghc962" "ghc9820230704"]) {
     # Musl cross only works on linux
     # aarch64 cross only works on linux
     inherit (lib.systems.examples) musl64 aarch64-multiplatform;
-  } // lib.optionalAttrs (system == "x86_64-linux" && nixpkgsName == "unstable" && __elem compiler-nix-name ["ghc927" "ghc928"]) {
+  } // lib.optionalAttrs (system == "x86_64-linux" && nixpkgsName == "unstable" && builtins.elem compiler-nix-name ["ghc927" "ghc928"]) {
     # TODO fix this for the compilers we build with hadrian (ghc >=9.4)
     inherit (lib.systems.examples) aarch64-multiplatform-musl;
-  } // lib.optionalAttrs (system == "aarch64-linux" && nixpkgsName == "unstable" && __elem compiler-nix-name ["ghc927" "ghc928" "ghc947" "ghc962" "ghc9820230704"]) {
+  } // lib.optionalAttrs (system == "aarch64-linux" && nixpkgsName == "unstable" && builtins.elem compiler-nix-name ["ghc927" "ghc928" "ghc947" "ghc962" "ghc9820230704"]) {
     inherit (lib.systems.examples) aarch64-multiplatform-musl;
   };
   isDisabled = d: d.meta.disabled or false;
 in
-dimension "Nixpkgs version" nixpkgsVersions (nixpkgsName: nixpkgs-pin:
-  let pinnedNixpkgsSrc = sources.${nixpkgs-pin};
-      evalPackages = import pinnedNixpkgsSrc (nixpkgsArgs // { system = evalSystem; });
+dimension "Nixpkgs version" nixpkgsVersions (nixpkgsName: pinnedNixpkgsSrc:
+  let evalPackages = import pinnedNixpkgsSrc (nixpkgsArgs // { system = evalSystem; });
   in dimension "GHC version" (compilerNixNames nixpkgsName evalPackages) (compiler-nix-name: {runTests}:
       let pkgs = import pinnedNixpkgsSrc (nixpkgsArgs // { inherit system; });
           build = import ./build.nix { inherit pkgs evalPackages ifdLevel compiler-nix-name haskellNix; };

default.nix

@@ -1,21 +1,42 @@
-{...}@args:
+{ system ? builtins.currentSystem
+, sourcesOverride ? { }
+, checkMaterialization ? false
+, ...
+}:
 
 let
-  pins = (__fromJSON (__readFile ./flake.lock)).nodes;
-  nixpkgsPin = pins.nixpkgs-2211.locked;
-  flakeCompatPin = pins.flake-compat.locked;
-  nixpkgsSrc =
+  lock = builtins.fromJSON (builtins.readFile ./flake.lock);
+
+  # NOTE: This has to be whitelisted in restricted evaluation mode
+  flake-compat =
+    with lock.nodes.flake-compat.locked;
     builtins.fetchTarball {
-      url = "https://github.com/NixOS/nixpkgs/archive/${nixpkgsPin.rev}.tar.gz";
-      sha256 = nixpkgsPin.narHash;
+      url = "https://github.com/input-output-hk/flake-compat/archive/${rev}.tar.gz";
+      sha256 = narHash;
     };
-  pkgs = args.pkgs or (import nixpkgsSrc {});
-  flake-compat =
-    pkgs.fetchzip {
-      url = "https://github.com/input-output-hk/flake-compat/archive/${flakeCompatPin.rev}.tar.gz";
-      sha256 = flakeCompatPin.narHash;
+
+  # With flake-compat you will end up fetching the flake inputs with
+  # builtins.fetchTarball. This is simply because you don't have access to any
+  # nixpkgs before fetching the inputs.
+  #
+  # This won't work in restricted evaluation mode.
+  #
+  # Under the mild assumtion that https://github.com/NixOS is whitelisted, we
+  # can manually fetch nixpkgs and let flake-compat fetch the rest of the
+  # inputs with the nixpkgs just fetched.
+  #
+  # Manually fetch nixpkgs
+  nixpkgs =
+    with lock.nodes.nixpkgs.locked;
+    builtins.fetchTarball {
+      url = "https://github.com/NixOS/nixpkgs/archive/${rev}.tar.gz";
+      sha256 = narHash;
     };
-  self = import flake-compat {
+  #
+  # Instantiate the flake fetching the other inputs with the nixpkgs already
+  # fetched
+  self = (import flake-compat {
+    pkgs = import nixpkgs { };
     # We bypass flake-compat's rootSrc cleaning by evading its detection of this as a git
     # repo.
     # This is done for 3 reasons:
@@ -26,7 +47,49 @@ let
     #   in `test/default.nix`).  If `flake-compat` copies the whole git repo, any change to the
     #   repo causes a change of input for all tests.
     src = { outPath = ./.; };
-    inherit pkgs;
+    override-inputs = sourcesOverride;
+  }).defaultNix;
+
+  inherit (self.inputs.nixpkgs) lib;
+
+  # coming from internal.compat
+  overlays = [ self.overlay ]
+    ++ lib.optional checkMaterialization
+    (final: prev: {
+      haskell-nix = prev.haskell-nix // {
+        checkMaterialization = true;
+      };
+    });
+  nixpkgsArgs = {
+    inherit overlays;
+    inherit (self) config;
   };
-in self.defaultNix // (self.defaultNix.internal.compat
-({ system = args.pkgs.system or builtins.currentSystem; } // args))
+  pkgs = import self.inputs.nixpkgs (nixpkgsArgs // {
+    localSystem = { inherit system; };
+  });
+in
+self // {
+  inherit nixpkgsArgs pkgs;
+  inherit (nixpkgsArgs) config overlays;
+  sources = self.inputs;
+  allOverlays = self.overlays;
+  pkgs-2105 = import self.inputs.nixpkgs-2105 (nixpkgsArgs // {
+    localSystem = { inherit system; };
+  });
+  pkgs-2111 = import self.inputs.nixpkgs-2111 (nixpkgsArgs // {
+    localSystem = { inherit system; };
+  });
+  pkgs-2205 = import self.inputs.nixpkgs-2205 (nixpkgsArgs // {
+    localSystem = { inherit system; };
+  });
+  pkgs-2211 = import self.inputs.nixpkgs-2211 (nixpkgsArgs // {
+    localSystem = { inherit system; };
+  });
+  pkgs-2305 = import self.inputs.nixpkgs-2305 (nixpkgsArgs // {
+    localSystem = { inherit system; };
+  });
+  pkgs-unstable = import self.inputs.nixpkgs-unstable (nixpkgsArgs // {
+    localSystem = { inherit system; };
+  });
+  hix = import ./hix/default.nix { inherit pkgs; };
+}