Fix settings.<name>.cabalFlags implementation (#178)

* Fix cabalFlags implementation

* Improve impl; add test

* update changelog

---------

Co-authored-by: Sridhar Ratnakumar <srid@srid.ca>

CHANGELOG.md

@@ -9,7 +9,7 @@
   - `flake.haskellFlakeProjectModules`: Dropped all defaults, except the `output` module, which now exports `packages` and `settings`. Added a `defaults.projectModules.output` option that allows the user to override this module, or directly access the generated module.
   - Add `project.config.defaults.settings.default` defining sensible defaults for local packages.
   - Add `project.config.defaults.enable` to turn off all default settings en masse.
-  - Regressions in this PR: #169
+  - Regressions in this PR: #169, #178
 
 ## 0.3.0 (May 22, 2023)
 

nix/modules/project/settings/all.nix

@@ -199,12 +199,11 @@ in
       '';
       impl = flags: drv:
         let
-          enabled = lib.filterAttrs (_: v: v) flags;
-          disabled = lib.filterAttrs (_: v: !v) flags;
-          enableCabalFlags = fs: drv: builtins.foldl' enableCabalFlag drv fs;
-          disableCabalFlags = fs: drv: builtins.foldl' disableCabalFlag drv fs;
+          fns = lib.flip lib.mapAttrsToList flags (flag: enabled:
+            (if enabled then enableCabalFlag else disableCabalFlag) flag
+          );
         in
-        lib.pipe drv [ enableCabalFlag disableCabalFlag ];
+        lib.pipe drv fns;
     };
     patches = {
       type = types.listOf types.path;

test/simple/flake.nix

@@ -52,6 +52,11 @@
             # the 'foo' package, we must override it here using `lib.mkForce`.
             foo.source = lib.mkForce (inputs.haskell-multi-nix + /foo);
           };
+          settings = {
+            foo = {
+              cabalFlags.blah = true;
+            };
+          };
           devShell = {
             tools = hp: {
               # Adding a tool should make it available in devshell.