makeOverridablePythonPackage: simplify implementation and make compatible with <pkg>.overrideAttrs

pkgs/development/interpreters/python/python-packages-base.nix

@@ -14,27 +14,23 @@ let
 
   # Derivations built with `buildPythonPackage` can already be overridden with `override`, `overrideAttrs`, and `overrideDerivation`.
   # This function introduces `overridePythonAttrs` and it overrides the call to `buildPythonPackage`.
+  #
+  # Overridings specified through `overridePythonAttrs` will always be applied
+  # before those specified by `overrideAttrs`, even if invoked after them.
   makeOverridablePythonPackage =
     f:
     lib.mirrorFunctionArgs f (
       origArgs:
       let
-        args = lib.fix (
-          lib.extends (_: previousAttrs: {
-            passthru = (previousAttrs.passthru or { }) // {
-              overridePythonAttrs = newArgs: makeOverridablePythonPackage f (overrideWith newArgs);
-            };
-          }) (_: origArgs)
-        );
-        result = f args;
-        overrideWith = newArgs: args // (if pkgs.lib.isFunction newArgs then newArgs args else newArgs);
+        result = f origArgs;
+        overrideWith = newArgs: origArgs // lib.toFunction newArgs origArgs;
       in
-      if builtins.isAttrs result then
+      if lib.isAttrs result then
         result
-      else if builtins.isFunction result then
-        {
+        // {
           overridePythonAttrs = newArgs: makeOverridablePythonPackage f (overrideWith newArgs);
-          __functor = self: result;
+          overrideAttrs =
+            newArgs: makeOverridablePythonPackage (args: (f args).overrideAttrs newArgs) origArgs;
         }
       else
         result

pkgs/test/overriding.nix

@@ -390,15 +390,73 @@ let
 
   tests-python =
     let
-      p = pkgs.python3Packages.xpybutil.overridePythonAttrs (_: {
-        dontWrapPythonPrograms = true;
-      });
+      python-package-stub = pkgs.python3Packages.callPackage (
+        {
+          buildPythonPackage,
+          emptyDirectory,
+        }:
+        buildPythonPackage {
+          pname = "python-package-stub";
+          version = "0.1.0";
+          pyproject = true;
+          src = emptyDirectory;
+        }
+      ) { };
+      applyOverridePythonAttrs =
+        p:
+        p.overridePythonAttrs (previousAttrs: {
+          overridePythonAttrsFlag = previousAttrs.overridePythonAttrsFlag or 0 + 1;
+        });
+      overrideAttrsFooBar =
+        drv:
+        drv.overrideAttrs (
+          finalAttrs: previousAttrs: {
+            FOO = "a";
+            BAR = finalAttrs.FOO;
+          }
+        );
     in
     {
       overridePythonAttrs = {
-        expr = !lib.hasInfix "wrapPythonPrograms" p.postFixup;
+        expr = (applyOverridePythonAttrs python-package-stub).overridePythonAttrsFlag;
+        expected = 1;
+      };
+      overridePythonAttrs-nested = {
+        expr =
+          (applyOverridePythonAttrs (applyOverridePythonAttrs python-package-stub)).overridePythonAttrsFlag;
+        expected = 2;
+      };
+      overrideAttrs-overridePythonAttrs-test-overrideAttrs = {
+        expr = {
+          inherit (applyOverridePythonAttrs (overrideAttrsFooBar python-package-stub))
+            FOO
+            BAR
+            ;
+        };
+        expected = {
+          FOO = "a";
+          BAR = "a";
+        };
+      };
+      overrideAttrs-overridePythonAttrs-test-overridePythonAttrs = {
+        expr =
+          (applyOverridePythonAttrs (overrideAttrsFooBar python-package-stub)) ? overridePythonAttrsFlag;
         expected = true;
       };
+      overrideAttrs-overridePythonAttrs-test-commutation = {
+        expr = overrideAttrsFooBar (applyOverridePythonAttrs python-package-stub);
+        expected = applyOverridePythonAttrs (overrideAttrsFooBar python-package-stub);
+      };
+      chain-of-overrides = rec {
+        expr = lib.pipe python-package-stub [
+          (p: p.overrideAttrs { inherit (expected) a; })
+          (p: p.overridePythonAttrs { inherit (expected) b; })
+          (p: p.overrideAttrs { inherit (expected) c; })
+          (p: p.overridePythonAttrs { inherit (expected) d; })
+          (builtins.intersectAttrs expected)
+        ];
+        expected = lib.genAttrs [ "a" "b" "c" "d" ] lib.id;
+      };
     };
 
 in