Preserve overridden Stack compiler (fixes #2039) (#2041)

* Add test case for #2039

* Preserve overridden Stack compiler (fixes #2039)

Author: cydparser

lib/import-and-filter-project.nix

@@ -17,7 +17,9 @@ let
   projectSubDir'' = if projectSubDir == "" then "" else projectSubDir + "/"; # With trailing /
   project = import "${projectNix}${projectSubDir'}";
 in project // {
-    extras = hackage: let old = (project.extras hackage).packages; in {
+    extras = hackage: let
+      old = project.extras hackage;
+    in old // {
       packages = pkgs.lib.attrsets.mapAttrs (name: value:
         if builtins.isFunction value
           then value
@@ -56,6 +58,6 @@ in project // {
               package = oldPkg.package // {
                 isProject = (pkgs.lib).mkDefault packageInfo.isProject;
               };
-            }) old;
+            }) old.packages;
     };
   }

overlays/haskell.nix

@@ -121,7 +121,7 @@ final: prev: {
                   else module;
                 removeSpecialPackages = ps: removeAttrs ps [ "$locals" "$targets" "$everything" ];
             in mkPkgSet {
-                pkg-def = excludeBootPackages null pkg-def;
+                pkg-def = excludeBootPackages compiler.nix-name pkg-def;
                 pkg-def-extras = [ stack-pkgs.extras
                                    final.ghc-boot-packages.${compiler.nix-name}
                                  ]

test/default.nix

@@ -175,6 +175,7 @@ let
     with-packages = callTest ./with-packages { inherit util; };
     builder-haddock = callTest ./builder-haddock {};
     stack-simple = callTest ./stack-simple {};
+    stack-compiler = callTest ./stack-compiler {};
     stack-local-resolver = callTest ./stack-local-resolver {};
     stack-local-resolver-subdir = callTest ./stack-local-resolver-subdir {};
     stack-remote-resolver = callTest ./stack-remote-resolver {};

test/stack-compiler/.gitignore

@@ -0,0 +1 @@
+/.stack-work/

test/stack-compiler/Lib.hs

@@ -0,0 +1,4 @@
+module Lib where
+
+foo :: Int
+foo = 1

test/stack-compiler/default.nix

@@ -0,0 +1,16 @@
+{ stackProject', recurseIntoAttrs, testSrc, compiler-nix-name, evalPackages }:
+
+let
+  project = stackProject' {
+    src = testSrc "stack-compiler";
+    inherit evalPackages;
+  };
+  packages = project.hsPkgs;
+
+in recurseIntoAttrs {
+  meta.disabled = compiler-nix-name != "ghc947";
+  ifdInputs = {
+    inherit (project) stack-nix;
+  };
+  inherit (packages.stack-compiler.components) library;
+}

test/stack-compiler/stack-compiler.cabal

@@ -0,0 +1,7 @@
+cabal-version: 3.8
+name: stack-compiler
+version: 0.0.1
+
+library
+  exposed-modules: Lib
+  build-depends: base

test/stack-compiler/stack.yaml

@@ -0,0 +1,5 @@
+resolver: lts-21.9
+compiler: ghc-9.4.7
+compiler-check: match-exact
+packages:
+- .