From eb2a4ddc0643f295c3c108ce7530a24f28355942 Mon Sep 17 00:00:00 2001
From: Pavel Koneski <pavel.koneski@gmail.com>
Date: Sun, 18 Apr 2021 14:21:33 -0700
Subject: [PATCH 1/2] Enable some metaclass tests

---
 Src/IronPython/Runtime/Operations/PythonOps.cs |  3 +++
 Tests/test_metaclass.py                        | 18 +++++++++---------
 2 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/Src/IronPython/Runtime/Operations/PythonOps.cs b/Src/IronPython/Runtime/Operations/PythonOps.cs
index 57c40a078..af7d92c88 100644
--- a/Src/IronPython/Runtime/Operations/PythonOps.cs
+++ b/Src/IronPython/Runtime/Operations/PythonOps.cs
@@ -1332,6 +1332,9 @@ public static object MakeClass(FunctionCode funcCode, Func<CodeContext, CodeCont
             object? metaclass = null;
             if (keywords is not null && keywords.TryGetValueNoMissing("metaclass", out metaclass)) {
                 keywords.RemoveDirect("metaclass"); // keyword argument consumed
+                if (metaclass is null) {
+                    throw TypeError("metaclass cannot be 'None'"); // CPython: 'NoneType' object is not callable
+                }
             }
 
             return MakeClass(parentContext, name, bases, metaclass, keywords, selfNames, func(parentContext).Dict);
diff --git a/Tests/test_metaclass.py b/Tests/test_metaclass.py
index 92e6487fd..478877436 100644
--- a/Tests/test_metaclass.py
+++ b/Tests/test_metaclass.py
@@ -114,7 +114,7 @@ def method(self): return 10
             self.assertEqual(x.method(), 10)
 
         try_metaclass(type)
-        #try_metaclass(type(Old))  # bug 364938
+        try_metaclass(type(Old))
         try_metaclass(dash_attributes)
         try_metaclass(sub_type1)
 
@@ -167,7 +167,7 @@ class D2(object,metaclass=meta):
         # base order: how to see the effect of the order???
         for x in [
                     A1,
-                    #A2,        # bug 364991
+                    A2,
                 ]:
             for y in [B1, B2]:
                 class E(x, y):
@@ -195,19 +195,19 @@ class C4(object,metaclass=sub_type3):
 
         flag = 0
         class D(C1, C2): pass
-        #self.assertEqual(flag, 1)   # bug 364991
+        self.assertEqual(flag, 1)
         flag = 0
         class D(C2, C1): pass
-        #self.assertEqual(flag, 1)
+        self.assertEqual(flag, 1)
         flag = 0
         class D(C3, C4): pass  # C4 derive from C3
-        #self.assertEqual(flag, 120)
+        self.assertEqual(flag, 110)
         flag = 0
         class D(C3, C1, C4): pass
-        #self.assertEqual(flag, 120)
+        self.assertEqual(flag, 110)
         flag = 0
         class D(C4, C1): pass
-        #self.assertEqual(flag, 110)
+        self.assertEqual(flag, 110)
 
         def f1():
             class D(C2, C3): pass
@@ -218,7 +218,7 @@ class D(C2, C1, C3): pass
 
         for f in [
                 f1,
-                #f2,   # bug 364991
+                f2,
                 f3,
             ]:
             self.assertRaises(TypeError, f)
@@ -229,7 +229,7 @@ class C(object, metaclass=x):
                 pass
 
         for x in [
-                    #None,   # bug 364967
+                    None,
                     1,
                     [],
                     lambda name, bases, dict, extra: 1,

From a542d4c55ab39ddd110fdd9d5f72d133d0c30d19 Mon Sep 17 00:00:00 2001
From: Pavel Koneski <pavel.koneski@gmail.com>
Date: Mon, 19 Apr 2021 20:13:51 -0700
Subject: [PATCH 2/2] Remove Old/New classes

---
 Tests/test_metaclass.py | 29 ++++++++++++-----------------
 1 file changed, 12 insertions(+), 17 deletions(-)

diff --git a/Tests/test_metaclass.py b/Tests/test_metaclass.py
index 478877436..5364e544c 100644
--- a/Tests/test_metaclass.py
+++ b/Tests/test_metaclass.py
@@ -8,10 +8,7 @@
 
 # ref: http://docs.python.org/ref/metaclasses.html
 
-class Old:
-    def method(self): return 10
-
-class New(object):
+class SomeClass(object):
     def method(self): return 10
 
 def g_f_modify(new_base=None, new_name=None):
@@ -89,11 +86,11 @@ def _check(T):
             self.assertEqual(x.__class__.__name__, "D")
 
         for f in [ g_f_modify, g_c_modify ]:
-            class C(object, metaclass=f((New,), "D")):
+            class C(object, metaclass=f((SomeClass,), "D")):
                 pass
             _check(C)
 
-            class C(metaclass=f((New,), "D")):
+            class C(metaclass=f((SomeClass,), "D")):
                 pass
             _check(C)
 
@@ -114,7 +111,6 @@ def method(self): return 10
             self.assertEqual(x.method(), 10)
 
         try_metaclass(type)
-        try_metaclass(type(Old))
         try_metaclass(dash_attributes)
         try_metaclass(sub_type1)
 
@@ -145,23 +141,23 @@ def StartSomethingToday(self): pass
         self.assertTrue(hasattr(D, "start_something_today"))
 
     def test_find_metaclass(self):
+        # A1 hits a slightly different code path in some places than A2, same for B1, B2, etc.
         class A1: pass
         class A2(object): pass
+        self.assertEqual(A1.__class__, type)
         self.assertEqual(A2.__class__, type)
 
-        class B1(metaclass=dash_attributes):
-            pass
-        class B2(object, metaclass=dash_attributes):
-            pass
+        class B1(metaclass=dash_attributes): pass
+        class B2(object, metaclass=dash_attributes): pass
 
         meta = lambda *args: 100
 
-        class D1(metaclass=meta):
-            pass
+        class D1(metaclass=meta): pass
         self.assertEqual(D1, 100)
+        self.assertEqual(D1.__class__, int)
 
-        class D2(object,metaclass=meta):
-            pass
+        class D2(object,metaclass=meta): pass
+        self.assertEqual(D2, 100)
         self.assertEqual(D2.__class__, int)
 
         # base order: how to see the effect of the order???
@@ -234,8 +230,7 @@ class C(object, metaclass=x):
                     [],
                     lambda name, bases, dict, extra: 1,
                     lambda name, bases: 1,
-                    Old,
-                    New,
+                    SomeClass,
                 ]:
             self.assertRaises(TypeError, create, x)