wip: useCabalFromGHC, look into ghc environment files

Author: pranaysashank

.envrc

@@ -5,7 +5,7 @@
 let
   # Sort and remove duplicates from nonReinstallablePkgs.
   # That way changes to the order of nonReinstallablePkgs does not require rebuilds.
-  nonReinstallablePkgs' = __attrNames (lib.genAttrs nonReinstallablePkgs (x: x));
+  nonReinstallablePkgs' = let x = __attrNames (lib.genAttrs nonReinstallablePkgs (x: x)); in __trace x x;
 
   ghc = if enableDWARF then defaults.ghc.dwarf else defaults.ghc;
 
@@ -151,6 +151,7 @@ let
 
     for p in "''${pkgsHostTarget[@]}"; do
       if [ -e $p/envDep ]; then
+        echo "But not here"
         cat $p/envDep >> $configFiles/ghc-environment
       fi
       ${ lib.optionalString component.doExactConfig ''
@@ -221,7 +222,7 @@ let
     done
   '' + ''
     ${target-pkg} -v0 --package-db $configFiles/${packageCfgDir} recache
-  '';  
+  '';
   drv = runCommand "${ghc.targetPrefix}${fullName}-config" {
       nativeBuildInputs = [ghc];
       propagatedBuildInputs = libDeps;

builder/make-config-files.nix

@@ -22,6 +22,11 @@
       url = "github:haskell/cabal/3.6";
       flake = false;
     };
+
+    hackage-db = {
+      url = "github:michaelpj/hackage-db/83f819cb08742d3c86a83b407d45c1f6c1c7e299";
+      flake = false;
+    };
   };
 
   outputs =

flake.lock

@@ -73,7 +73,7 @@ let
   # nix module system for `nix-tools-unchecked` and `cabal-install-unchecked`.
   nix-tools = if args.nix-tools or null != null
     then args.nix-tools
-    else evalPackages.haskell-nix.nix-tools-unchecked;
+    else evalPackages.haskell-nix.nix-tools;
   cabal-install = nix-tools.exes.cabal;
   forName = pkgs.lib.optionalString (name != null) (" for " + name);
   nameAndSuffix = suffix: if name == null then suffix else name + "-" + suffix;
@@ -423,7 +423,7 @@ let
           # without the source available (we cleanSourceWith'd it),
           # this may not produce the right result.
           if supportHpack
-            then '' 
+            then ''
               echo No .cabal file found, running hpack on $hpackFile
               hpack $hpackFile
             ''
@@ -451,7 +451,7 @@ let
       # some packages that will be excluded by `index-state-max`
       # which is used by cabal (cached-index-state >= index-state-max).
       dotCabal {
-        inherit cabal-install nix-tools extra-hackage-tarballs;
+        inherit nix-tools extra-hackage-tarballs;
         extra-hackage-repos = fixedProject.repos;
         index-state = cached-index-state;
         sha256 = index-sha256-found;
@@ -462,6 +462,7 @@ let
           # packages used by the solver (cached-index-state >= index-state-max).
           pkgs.lib.optionalString (index-state != null) "--index-state=${index-state}"
         } \
+        -v3 \
         -w ${
           # We are using `-w` rather than `--with-ghc` here to override
           # the `with-compiler:` in the `cabal.project` file.

flake.nix

@@ -19,16 +19,16 @@ in {
       description = "The name of the ghc compiler to use eg. \"ghc884\"";
       # Map short version names to the latest GHC version.
       # TODO: perhaps combine this with the `latestVer` mapping in `overlays/boostrap.nix`.
-      apply = name:
-        let
-          fullName = pkgs.haskell-nix.resolve-compiler-name name;
-          ghc910FullName = pkgs.haskell-nix.resolve-compiler-name "ghc910X";
-          ghc911FullName = pkgs.haskell-nix.resolve-compiler-name "ghc911";
-        in
-        # cabal-install from hackage (3.10.1.0) does not build with GHC HEAD
-        if builtins.elem fullName [ ghc910FullName ghc911FullName ] && config.name == "cabal-install" && (builtins.elem config.version ["3.10.1.0" "3.10.2.0" "3.10.2.1"])
-          then "ghc964"
-          else pkgs.haskell-nix.resolve-compiler-name name;
+      # apply = name:
+      #   let
+      #     fullName = pkgs.haskell-nix.resolve-compiler-name name;
+      #     ghc910FullName = pkgs.haskell-nix.resolve-compiler-name "ghc910X";
+      #     ghc911FullName = pkgs.haskell-nix.resolve-compiler-name "ghc911";
+      #   in
+      #   # cabal-install from hackage (3.10.1.0) does not build with GHC HEAD
+      #   if builtins.elem fullName [ ghc910FullName ghc911FullName ] && config.name == "cabal-install" && (builtins.elem config.version ["3.10.1.0" "3.10.2.0" "3.10.2.1"])
+      #     then "ghc964"
+      #     else pkgs.haskell-nix.resolve-compiler-name name;
     };
     compilerSelection = mkOption {
       type = unspecified;

lib/call-cabal-project-to-nix.nix

@@ -17,49 +17,13 @@
 
       compiler = "ghc981";
 
-      nix-tools-overlays = final: prev: {
-        haskell = prev.haskell // {
-          packages = prev.haskell.packages // {
-            "${compiler}" = prev.haskell.packages."${compiler}".override
-              (old: {
-                overrides = final.lib.fold final.lib.composeExtensions
-                  (old.overrides or (_: _: { })) [
-                    (hfinal: hprev:
-                      let
-                        fetchFromHackage = pname: version: hash:
-                          hfinal.callHackageDirect {
-                            pkg = pname;
-                            ver = version;
-                            sha256 = hash;
-                          };
-                        ps-cabal-install-solver = (fetchFromHackage "cabal-install-solver" "3.10.2.1" "sha256-wNwp42fiEketjcKJwhv5etP5/bVGlDitnMryTLX+Z74=") {};
-                        ps-cabal-install = (fetchFromHackage "cabal-install" "3.10.2.1" "sha256-encWM587n+atIrbjHaNjNeavBoxmMsI1QXDS5AtOLoo=") {Cabal-described = null; Cabal-QuickCheck = null; Cabal-tree-diff = null; cabal-install-solver = ps-cabal-install-solver;};
-                      in {
-                        ps-cabal-install = ps-cabal-install;
-                        ps-cabal-install-solver = ps-cabal-install-solver;
-                    })
-                    (hfinal: hprev:
-                      {
-                        nix-tools = final.haskell.lib.dontCheck (final.haskell.lib.markUnbroken (hfinal.callCabal2nix "nix-tools" ./nix-tools {
-                          cabal-install = hfinal.ps-cabal-install;
-                          cabal-install-solver = hfinal.ps-cabal-install-solver;
-                        }));
-
-                        hackage-db = hfinal.callCabal2nix "hackage-db" "${inputs.hackage-db}" {};
-                    })
-                  ];
-              });
-          };
-        };
-      };
-
       # keep it simple (from https://ayats.org/blog/no-flake-utils/)
       forAllSystems = f:
         nixpkgs.lib.genAttrs systems (system:
           f (import nixpkgs {
             inherit system;
             overlays = [
-              nix-tools-overlays
+              (import ./overlay.nix { hackage-db-src = "${inputs.hackage-db}"; })
             ];
           }));
 
@@ -68,6 +32,7 @@
       packages = forAllSystems (pkgs:
         {
           nix-tools = pkgs.haskell.packages.ghc981.nix-tools;
+          pkgs = pkgs;
         });
     };