test_trailing_placeholders and bug fix

Author: dg-pb

Lib/functools.py

@@ -310,7 +310,15 @@ def _partial_prepare_merger(args):
         else:
             order.append(i)
     phcount = j - nargs
-    merger = itemgetter(*order) if phcount else None
+    if phcount:
+        if nargs == 1:
+            i = order[0]
+            def merger(all_args):
+                return (all_args[i],)
+        else:
+            merger = itemgetter(*order)
+    else:
+        merger = None
     return phcount, merger
 
 def _partial_repr(self):
@@ -403,7 +411,8 @@ def __setstate__(self, state):
 
         phcount, merger = _partial_prepare_merger(args)
 
-        args = tuple(args) # just in case it's a subclass
+        if type(args) is not tuple:
+            args = tuple(args)       # just in case it's a subclass
         if kwds is None:
             kwds = {}
         elif type(kwds) is not dict: # XXX does it need to be *exactly* dict?

Lib/test/test_functools.py

@@ -211,16 +211,16 @@ def foo(bar):
         p2.new_attr = 'spam'
         self.assertEqual(p2.new_attr, 'spam')
 
-    # def test_placeholders_trailing_trim(self):
-    #     PH = self.module.Placeholder
-    #     for args, call_args, expected_args in [
-    #                 [(PH,), (), ()],
-    #                 [(0, PH), (), (0,)],
-    #                 [(0, PH, 1, PH, PH, PH), (2,), (0, 2, 1)]
-    #             ]:
-    #         actual_args, actual_kwds = self.partial(capture, *args)(*call_args)
-    #         self.assertEqual(actual_args, expected_args)
-    #         self.assertEqual(actual_kwds, {})
+    def test_trailing_placeholders(self):
+        PH = self.module.Placeholder
+        for args, call_args, expected_args in [
+                    [(PH,), (1,), (1,)],
+                    [(0, PH), (1,), (0, 1)],
+                    [(0, PH, 2, PH, PH), (1, 3, 4), (0, 1, 2, 3, 4)]
+                ]:
+            actual_args, actual_kwds = self.partial(capture, *args)(*call_args)
+            self.assertEqual(actual_args, expected_args)
+            self.assertEqual(actual_kwds, {})
 
     def test_placeholders(self):
         PH = self.module.Placeholder
@@ -373,12 +373,6 @@ def test_setstate(self):
             f()
         self.assertEqual(f(2), ((2, 1), dict(a=10)))
 
-        # # Trailing Placeholder error
-        # f = self.partial(signature)
-        # msg_regex = re.escape("unexpected trailing Placeholders")
-        # with self.assertRaisesRegex(TypeError, f'^{msg_regex}$') as cm:
-        #     f.__setstate__((capture, (1, PH), dict(a=10), dict(attr=[])))
-
     def test_setstate_errors(self):
         f = self.partial(signature)
         self.assertRaises(TypeError, f.__setstate__, (capture, (), {}))