Choose proper llvm version for llvm-hs and make stack infra work like stack does (#1724)

* update llvm-hs llvm from 11 to 12

* allow passing version args to build-tools; fix llvm-hs build-tools, pass allRefs to builtins.fetchGit to allow fetching non-standard-refs (to mirror stack behaviour)

Author: MangoIV

builder/comp-builder.nix

@@ -235,10 +235,16 @@ let
         "--ghc-options=-j1"
     );
 
+  # the build-tools version might be depending on the version of the package, similarly to patches
   executableToolDepends =
     (lib.concatMap (c: if c.isHaskell or false
       then builtins.attrValues (c.components.exes or {})
-      else [c]) build-tools) ++
+      else [c]) 
+      (builtins.filter (x: !(isNull x))
+      (map 
+        (p: if builtins.isFunction p
+          then p { inherit  (package.identifier) version; inherit revision; }
+          else p) build-tools))) ++
     lib.optional (pkgconfig != []) buildPackages.cabalPkgConfigWrapper;
 
   # Unfortunately, we need to wrap ghc commands for cabal builds to

builder/setup-builder.nix

@@ -34,11 +34,18 @@ let
       ;
   };
 
-  executableToolDepends =
+  # the build-tools version might be depending on the version of the package, similarly to patches
+  executableToolDepends = 
+    let inherit (component) pkgconfig build-tools; in
     (lib.concatMap (c: if c.isHaskell or false
       then builtins.attrValues (c.components.exes or {})
-      else [c]) component.build-tools) ++
-    lib.optional (component.pkgconfig != []) buildPackages.cabalPkgConfigWrapper;
+      else [c]) 
+      (builtins.filter (x: !(isNull x))
+      (map 
+        (p: if builtins.isFunction p
+          then p { inherit  (package.identifier) version; inherit revision; }
+          else p) build-tools))) ++
+    lib.optional (pkgconfig != []) buildPackages.cabalPkgConfigWrapper;
 
   drv =
     stdenv.mkDerivation ({

lib/stack-cache-generator.nix

@@ -98,6 +98,7 @@ concatMap (dep:
                 else builtins.fetchGit ({
                   inherit (dep) url rev;
                   submodules = true;
+                  allRefs = true;
                 } // evalPackages.lib.optionalAttrs (branch != null) { ref = branch; });
         in map (subdir: {
                 name = cabalName "${pkgsrc}/${subdir}";

modules/configuration-nix.nix

@@ -91,7 +91,18 @@ in {
 
   packages.discount.components.library.libs = pkgs.lib.mkForce [ pkgs.discount ];
 
-  packages.llvm-hs.components.library.build-tools = pkgs.lib.mkForce [ pkgs.llvm ];
+  packages.llvm-hs.components.library.build-tools = pkgs.lib.mkForce [ 
+    (fromUntil "5.0.0" "6" pkgs.llvmPackages_5.llvm)
+    (fromUntil "6.0.0" "7" pkgs.llvmPackages_6.llvm)
+    (fromUntil "7.0.0" "8" pkgs.llvmPackages_7.llvm)
+    (fromUntil "8.0.0" "9" pkgs.llvmPackages_8.llvm)
+    (fromUntil "9.0.0" "12" pkgs.llvmPackages_9.llvm)
+    (fromUntil "12.0.0" "15" pkgs.llvmPackages_12.llvm)
+    # NOTE: we currently don't have a llvm versoin > 12 that has a tag 
+    #       in nixpkgs, so we probably can't build `llvm-hs > 12`, there 
+    #       is however a head version of llvm in nixpkgs, which we might 
+    #       be able to use if that case were to occur
+  ];
 
   packages.BNFC.components.tests.doctests.build-tools = [
     config.hsPkgs.buildPackages.alex