Builtins: refactor attrGetOr

Author: Anton-Latukha

src/Nix/Builtins.hs

@@ -885,29 +885,21 @@ builtinsBuiltinNix
   => m (NValue t f m)
 builtinsBuiltinNix = throwError $ ErrorCall "HNix does not provide builtins.builtins at the moment. Using builtins directly should be preferred"
 
-attrGetOr'
+-- a safer version of `attrsetGet`
+attrGetOr
   :: forall e t f m v a
    . (MonadNix e t f m, FromValue v m (NValue t f m))
-  => AttrSet (NValue t f m)
-  -> VarName
-  -> m a
+  => a
   -> (v -> m a)
+  -> VarName
+  -> AttrSet (NValue t f m)
   -> m a
-attrGetOr' attrs n d f =
+attrGetOr fallback fun name attrs =
   maybe
-    d
-    (f <=< fromValue)
-    (M.lookup n attrs)
+    (pure fallback)
+    (fun <=< fromValue)
+    (M.lookup name attrs)
 
-attrGetOr
-  :: forall e t f m v a
-   . (MonadNix e t f m, FromValue v m (NValue t f m))
-  => AttrSet (NValue t f m)
-  -> VarName
-  -> a
-  -> (v -> m a)
-  -> m a
-attrGetOr attrs name fallback = attrGetOr' attrs name (pure fallback)
 
 --  NOTE: It is a part of the implementation taken from:
 --  https://github.com/haskell-nix/hnix/pull/755
@@ -920,8 +912,8 @@ pathNix arg =
 
     -- TODO: Fail on extra args
     -- XXX: This is a very common pattern, we could factor it out
-    name      <- toText <$> attrGetOr attrs "name"      (takeFileName path) (fmap (coerce . toString) . fromStringNoContext)
-    recursive <- attrGetOr attrs "recursive" True          pure
+    name      <- toText <$> attrGetOr (takeFileName path) (fmap (coerce . toString) . fromStringNoContext) "name" attrs
+    recursive <- attrGetOr True pure "recursive" attrs
 
     Right (coerce . toText . coerce @StorePath @String -> s) <- addToStore name path recursive False
     -- TODO: Ensure that s matches sha256 when not empty