Fix setup-depends dependencies

builder/default.nix

@@ -6,6 +6,12 @@ let
     inherit ghc haskellLib makeConfigFiles ghcForComponent hsPkgs;
   };
 
+  setup-builder = haskellLib.weakCallPackage pkgs ./setup-builder.nix {
+    ghc = buildGHC;
+    hsPkgs = hsPkgs.buildPackages;
+    inherit haskellLib nonReinstallablePkgs makeSetupConfigFiles;
+  };
+
   # Wraps GHC to provide dependencies in a way that works for both the
   # component builder and for nix-shells.
   ghcForComponent = import ./ghc-for-component-wrapper.nix {
@@ -19,6 +25,12 @@ let
   makeConfigFiles = haskellLib.weakCallPackage pkgs ./make-config-files.nix {
     inherit ghc haskellLib nonReinstallablePkgs;
   };
+  # When building setup depends we need to use the build systems GHC and Packages
+  makeSetupConfigFiles = haskellLib.weakCallPackage buildPackages ./make-config-files.nix {
+    inherit haskellLib nonReinstallablePkgs;
+    ghc = buildGHC;
+  };
+
 
   hoogleLocal = let
     nixpkgsHoogleLocal = import (pkgs.path + /pkgs/development/haskell-modules/hoogle.nix);
@@ -45,7 +57,7 @@ in {
   # Build a Haskell package from its config.
   # TODO: this pkgs is the adjusted pkgs, but pkgs.pkgs is unadjusted
   build-package = haskellLib.weakCallPackage pkgs ./hspkg-builder.nix {
-    inherit haskellLib ghc buildGHC comp-builder;
+    inherit haskellLib ghc buildGHC comp-builder setup-builder;
   };
 
   inherit shellFor;

builder/hspkg-builder.nix

@@ -1,4 +1,4 @@
-{ pkgs, buildPackages, stdenv, lib, haskellLib, ghc, buildGHC, fetchurl, runCommand, pkgconfig, comp-builder }:
+{ pkgs, buildPackages, stdenv, lib, haskellLib, ghc, buildGHC, fetchurl, runCommand, comp-builder, setup-builder }:
 
 
 { flags
@@ -38,26 +38,9 @@ let
 
   setup = if package.buildType == "Simple"
     then defaultSetup
-    else stdenv.mkDerivation {
-      name = "${name}-setup";
-      nativeBuildInputs = [buildGHC];
-      inherit src;
-      phases = ["unpackPhase" "buildPhase" "installPhase"];
-      buildPhase = ''
-        for f in Setup.hs Setup.lhs; do
-          if [ -f $f ]; then
-            echo Compiling package $f
-            ghc $f --make -o ./Setup
-            setup=$(pwd)/Setup
-          fi
-        done
-        [ -f ./Setup ] || (echo Failed to build Setup && exit 1)
-      '';
-
-      installPhase = ''
-        mkdir -p $out/bin
-        install ./Setup $out/bin/Setup
-      '';
+    else setup-builder {
+      setup-depends = package.setup-depends;
+      inherit package name src flags;
     };
 
   buildComp = componentId: component: comp-builder {

builder/setup-builder.nix

@@ -0,0 +1,46 @@
+{ stdenv, lib, buildPackages, haskellLib, ghc, nonReinstallablePkgs, hsPkgs, makeSetupConfigFiles }:
+
+{ setup-depends, package, name, src, flags }:
+
+let
+  fullName = "${name}-setup";
+
+  includeGhcPackage = lib.any (p: p.identifier.name == "ghc") setup-depends;
+
+  configFiles = makeSetupConfigFiles {
+    inherit (package) identifier;
+    inherit fullName flags;
+    component = {
+      depends = setup-depends;
+      libs = [];
+      frameworks = [];
+      doExactConfig = false;
+    };
+  }; 
+
+in
+ stdenv.lib.fix (drv:
+    stdenv.mkDerivation {
+      name = "${fullName}";
+      inherit src;
+      nativeBuildInputs = [ghc];
+
+      CABAL_CONFIG = configFiles + /cabal.config;
+      phases = ["unpackPhase" "buildPhase" "installPhase"];
+      buildPhase = ''
+        for f in Setup.hs Setup.lhs; do
+          if [ -f $f ]; then
+            echo Compiling package $f
+            ghc $f '' + (if includeGhcPackage then "-package ghc " else "")
+                + ''-package-db ${configFiles}/package.conf.d --make -o ./Setup
+            setup=$(pwd)/Setup
+          fi
+        done
+        [ -f ./Setup ] || (echo Failed to build Setup && exit 1)
+      '';
+
+      installPhase = ''
+        mkdir -p $out/bin
+        install ./Setup $out/bin/Setup
+      '';
+    })

nix-tools/default.nix

@@ -1,4 +1,4 @@
-{ lib, symlinkJoin, makeWrapper
+{ pkgs, lib, symlinkJoin, makeWrapper
 , hpack, git, nix, nix-prefetch-git
 , fetchExternal, cleanSourceHaskell, mkCabalProjectPkgSet }:
 
@@ -8,6 +8,14 @@ let
     specJSON = ./nix-tools-src.json;
     override = "nix-tools-src";
   });
+  # we need to patch Cabal, as its data directory logic is broken for component builds, which haskell.nix
+  # uses excessively. See issue https://github.com/haskell/cabal/issues/5862, and the fix for Cabal 3.0
+  # in https://github.com/haskell/cabal/pull/6055. We apply the haskell/cabal#6055 here.
+  cabalPatch = pkgs.fetchpatch {
+    url = "https://patch-diff.githubusercontent.com/raw/haskell/cabal/pull/6055.diff";
+    sha256 = "145g7s3z9q8d18pxgyngvixgsm6gmwh1rgkzkhacy4krqiq0qyvx";
+    stripLen = 1;
+  };
 
   pkgSet = mkCabalProjectPkgSet {
     plan-pkgs = import ./pkgs.nix;
@@ -22,6 +30,12 @@ let
       {
         packages.nix-tools.src = src;
       }
+
+      ({ config, ...}: {
+        packages = {
+          Cabal.patches = [ cabalPatch ];
+        };
+      })
     ];
   };