From 4f407ed2d4cbb3186877c24a7a60bfb1730b75c7 Mon Sep 17 00:00:00 2001
From: Andrea Bedini <andrea.bedini@tweag.io>
Date: Thu, 2 Feb 2023 16:49:31 +0800
Subject: [PATCH 1/3] First attempt

---
 builder/comp-builder.nix            |  2 +-
 builder/hspkg-builder.nix           |  4 ---
 lib/call-cabal-project-to-nix.nix   |  3 ---
 overlays/ghc-packages.nix           |  2 +-
 test/with-nixpkgs-ghc/default.nix   | 38 +++++++++++++++++++++++++++++
 test/with-nixpkgs-ghc/empty/.almost |  0
 6 files changed, 40 insertions(+), 9 deletions(-)
 create mode 100644 test/with-nixpkgs-ghc/default.nix
 create mode 100644 test/with-nixpkgs-ghc/empty/.almost

diff --git a/builder/comp-builder.nix b/builder/comp-builder.nix
index 7092a8b8e7..bcca8c11a0 100644
--- a/builder/comp-builder.nix
+++ b/builder/comp-builder.nix
@@ -82,7 +82,7 @@ let self =
 , enableTSanRTS ? false
 
 # LLVM
-, useLLVM ? ghc.useLLVM
+, useLLVM ? false
 , smallAddressSpace ? false
 
 }@drvArgs:
diff --git a/builder/hspkg-builder.nix b/builder/hspkg-builder.nix
index dd99d061b6..a0de9d127c 100644
--- a/builder/hspkg-builder.nix
+++ b/builder/hspkg-builder.nix
@@ -18,10 +18,6 @@ config:
 , ...
 }@pkg:
 
-assert (if ghc.isHaskellNixCompiler or false then true
-  else throw ("It is likely you used `haskell.compiler.X` instead of `haskell-nix.compiler.X`"
-    + pkgs.lib.optionalString (name != null) (" for " + name)));
-
 let
   # Some packages bundled with GHC are not the same as they are in hackage.
   bundledSrc = {
diff --git a/lib/call-cabal-project-to-nix.nix b/lib/call-cabal-project-to-nix.nix
index bc0f5c3577..ecaf102428 100644
--- a/lib/call-cabal-project-to-nix.nix
+++ b/lib/call-cabal-project-to-nix.nix
@@ -107,9 +107,6 @@ let
               pkgs.haskell-nix.compiler."${compiler-nix-name}";
 
 in
-  assert (if ghc'.isHaskellNixCompiler or false then true
-    else throw ("It is likely you used `haskell.compiler.X` instead of `haskell-nix.compiler.X`"
-      + forName));
 
 let
   ghc = ghc';
diff --git a/overlays/ghc-packages.nix b/overlays/ghc-packages.nix
index 0a8870d287..99d39b72d2 100644
--- a/overlays/ghc-packages.nix
+++ b/overlays/ghc-packages.nix
@@ -163,7 +163,7 @@ in rec {
               inherit subDir;
               includeSiblings = true;
             }
-            else "${ghc.passthru.configured-src}/${subDir}";
+            else "${ghc.configured-src}/${subDir}";
         nix = callCabal2Nix ghcName "${ghcName}-${pkgName}" src;
       }) (ghc-extra-pkgs ghc.version))
     final.buildPackages.haskell-nix.compiler;
diff --git a/test/with-nixpkgs-ghc/default.nix b/test/with-nixpkgs-ghc/default.nix
new file mode 100644
index 0000000000..84c62de04a
--- /dev/null
+++ b/test/with-nixpkgs-ghc/default.nix
@@ -0,0 +1,38 @@
+let
+
+  haskell-nix = import ../../default.nix { };
+  nixpkgs = haskell-nix.inputs.nixpkgs.outPath;
+
+  o2 = (
+    final: prev: {
+      haskell-nix = prev.haskell-nix // {
+        compiler = prev.haskell-nix.compiler // {
+          ghc8107 = prev.haskell.compiler.ghc8107 // {
+            # Add stuff not in nixpkgs ghc
+            configured-src = prev.haskell-nix.compiler.ghc8107.configured-src; # Needed for reinstallableLibGhc to work
+          };
+        };
+      };
+    }
+  );
+
+  pkgs = import nixpkgs {
+    system = __currentSystem;
+    inherit (haskell-nix) config;
+    overlays = [
+      # haskell-nix.overlays.haskell
+      # haskell-nix.overlays.tools
+      haskell-nix.overlay
+      o2
+    ];
+  };
+
+  prj = pkgs.haskell-nix.cabalProject {
+    src = ./empty;
+    cabalProject = "extra-packages: lens";
+    compiler-nix-name = "ghc8107";
+  };
+in
+
+prj.plan-nix
+
diff --git a/test/with-nixpkgs-ghc/empty/.almost b/test/with-nixpkgs-ghc/empty/.almost
new file mode 100644
index 0000000000..e69de29bb2

From 9085614f00a8abe453cf62dd5a7a992a58f3b782 Mon Sep 17 00:00:00 2001
From: Andrea Bedini <andrea.bedini@tweag.io>
Date: Sun, 5 Feb 2023 12:30:54 +0800
Subject: [PATCH 2/3] WIP

---
 test/with-nixpkgs-ghc/default.nix                      | 10 ++++------
 .../empty/{.almost => almost/.gitkeep}                 |  0
 2 files changed, 4 insertions(+), 6 deletions(-)
 rename test/with-nixpkgs-ghc/empty/{.almost => almost/.gitkeep} (100%)

diff --git a/test/with-nixpkgs-ghc/default.nix b/test/with-nixpkgs-ghc/default.nix
index 84c62de04a..cb8e884e45 100644
--- a/test/with-nixpkgs-ghc/default.nix
+++ b/test/with-nixpkgs-ghc/default.nix
@@ -1,3 +1,4 @@
+{ with-nixpkgs ? true }:
 let
 
   haskell-nix = import ../../default.nix { };
@@ -17,14 +18,12 @@ let
   );
 
   pkgs = import nixpkgs {
-    system = __currentSystem;
     inherit (haskell-nix) config;
     overlays = [
-      # haskell-nix.overlays.haskell
-      # haskell-nix.overlays.tools
       haskell-nix.overlay
-      o2
-    ];
+    ]
+    ++
+    (if with-nixpkgs then [ o2 ] else [ ]);
   };
 
   prj = pkgs.haskell-nix.cabalProject {
@@ -35,4 +34,3 @@ let
 in
 
 prj.plan-nix
-
diff --git a/test/with-nixpkgs-ghc/empty/.almost b/test/with-nixpkgs-ghc/empty/almost/.gitkeep
similarity index 100%
rename from test/with-nixpkgs-ghc/empty/.almost
rename to test/with-nixpkgs-ghc/empty/almost/.gitkeep

From 99e5334b31f85a3be20ac5e6e009df19e9af9427 Mon Sep 17 00:00:00 2001
From: Andrea Bedini <andrea.bedini@tweag.io>
Date: Sun, 5 Feb 2023 20:21:46 +0800
Subject: [PATCH 3/3] WIP

This seems to work. Revert a couple of unnecessary changes.
---
 builder/comp-builder.nix          |  2 +-
 overlays/ghc-packages.nix         |  2 +-
 test/with-nixpkgs-ghc/default.nix | 60 ++++++++++++++++++++++++++++---
 3 files changed, 57 insertions(+), 7 deletions(-)

diff --git a/builder/comp-builder.nix b/builder/comp-builder.nix
index bcca8c11a0..7092a8b8e7 100644
--- a/builder/comp-builder.nix
+++ b/builder/comp-builder.nix
@@ -82,7 +82,7 @@ let self =
 , enableTSanRTS ? false
 
 # LLVM
-, useLLVM ? false
+, useLLVM ? ghc.useLLVM
 , smallAddressSpace ? false
 
 }@drvArgs:
diff --git a/overlays/ghc-packages.nix b/overlays/ghc-packages.nix
index 99d39b72d2..0a8870d287 100644
--- a/overlays/ghc-packages.nix
+++ b/overlays/ghc-packages.nix
@@ -163,7 +163,7 @@ in rec {
               inherit subDir;
               includeSiblings = true;
             }
-            else "${ghc.configured-src}/${subDir}";
+            else "${ghc.passthru.configured-src}/${subDir}";
         nix = callCabal2Nix ghcName "${ghcName}-${pkgName}" src;
       }) (ghc-extra-pkgs ghc.version))
     final.buildPackages.haskell-nix.compiler;
diff --git a/test/with-nixpkgs-ghc/default.nix b/test/with-nixpkgs-ghc/default.nix
index cb8e884e45..401dfb0084 100644
--- a/test/with-nixpkgs-ghc/default.nix
+++ b/test/with-nixpkgs-ghc/default.nix
@@ -4,14 +4,63 @@ let
   haskell-nix = import ../../default.nix { };
   nixpkgs = haskell-nix.inputs.nixpkgs.outPath;
 
+  fix = final: prev: compiler-nix-name:
+    let
+      haskell-nix-ghc = prev.haskell-nix.compiler.${compiler-nix-name};
+      nixpkgs-ghc = prev.haskell.compiler.${compiler-nix-name};
+
+      exactDepOut =
+        pkgs.runCommand "${nixpkgs-ghc.name}-exactDeps" { }
+          ''
+            mkdir -p $out
+            ${nixpkgs-ghc}/bin/ghc-pkg --version
+            for P in $(${nixpkgs-ghc}/bin/ghc-pkg list --simple-output | sed 's/-[0-9][0-9.]*//g'); do
+              mkdir -p $out/exactDeps/$P
+              touch $out/exactDeps/$P/configure-flags
+              touch $out/exactDeps/$P/cabal.config
+
+              if id=$(${nixpkgs-ghc}/bin/ghc-pkg field $P id --simple-output); then
+                echo "--dependency=$P=$id" >> $out/exactDeps/$P/configure-flags
+              elif id=$(${nixpkgs-ghc}/bin/ghc-pkg field "z-$P-z-*" id --simple-output); then
+                name=$(${nixpkgs-ghc}/bin/ghc-pkg field "z-$P-z-*" name --simple-output)
+                # so we are dealing with a sublib. As we build sublibs separately, the above
+                # query should be safe.
+                echo "--dependency=''${name#z-$P-z-}=$id" >> $out/exactDeps/$P/configure-flags
+              fi
+              if ver=$(${nixpkgs-ghc}/bin/ghc-pkg field $P version --simple-output); then
+                echo "constraint: $P == $ver" >> $out/exactDeps/$P/cabal.config
+                echo "constraint: $P installed" >> $out/exactDeps/$P/cabal.config
+              fi
+            done
+
+            mkdir -p $out/evalDeps
+            for P in $(${nixpkgs-ghc}/bin/ghc-pkg list --simple-output | sed 's/-[0-9][0-9.]*//g'); do
+              touch $out/evalDeps/$P
+              if id=$(${nixpkgs-ghc}/bin/ghc-pkg field $P id --simple-output); then
+                echo "package-id $id" >> $out/evalDeps/$P
+              fi
+            done
+          '';
+    in
+    pkgs.symlinkJoin {
+      paths = [ nixpkgs-ghc exactDepOut ];
+
+      name = "${nixpkgs-ghc.name}-with-evalDeps";
+      inherit (nixpkgs-ghc) version;
+
+      # BLAH
+      inherit (haskell-nix-ghc) passthru;
+      # enableShared = true;
+      # targetPrefix = "";
+      # passthru.configured-src = haskell-nix-ghc.passthru.configured-src;
+      # useLLVM = false;
+    };
+
   o2 = (
     final: prev: {
       haskell-nix = prev.haskell-nix // {
         compiler = prev.haskell-nix.compiler // {
-          ghc8107 = prev.haskell.compiler.ghc8107 // {
-            # Add stuff not in nixpkgs ghc
-            configured-src = prev.haskell-nix.compiler.ghc8107.configured-src; # Needed for reinstallableLibGhc to work
-          };
+          ghc8107 = fix final prev "ghc8107";
         };
       };
     }
@@ -23,7 +72,8 @@ let
       haskell-nix.overlay
     ]
     ++
-    (if with-nixpkgs then [ o2 ] else [ ]);
+    (if with-nixpkgs then [ o2 ] else [ ])
+    ;
   };
 
   prj = pkgs.haskell-nix.cabalProject {