CR changes

Author: dg-pb

Lib/functools.py

@@ -343,10 +343,8 @@ def _partial_new(cls, func, /, *args, **keywords):
                 if nargs > pto_phcount:
                     tot_args += args[pto_phcount:]
             phcount, merger = _partial_prepare_merger(tot_args)
-        elif pto_phcount:   # not args and pto_phcount
+        else:   # works for both pto_phcount == 0 and != 0
             phcount, merger = pto_phcount, func._merger
-        else:               # not args and not pto_phcount
-            phcount, merger = 0, None
         keywords = {**func.keywords, **keywords}
         func = func.func
     else:

Lib/inspect.py

@@ -1933,7 +1933,10 @@ def _signature_get_partial(wrapped_sig, partial, extra_args=()):
                 # If positional-only parameter is bound by partial,
                 # it effectively disappears from the signature
                 # However, if it is a Placeholder it is not removed
-                if arg_value is not functools.Placeholder:
+                # And also looses default value
+                if arg_value is functools.Placeholder:
+                    new_params[param_name] = param.replace(default=_empty)
+                else:
                     new_params.pop(param_name)
                 continue
 
@@ -1957,9 +1960,13 @@ def _signature_get_partial(wrapped_sig, partial, extra_args=()):
                 else:
                     # was passed as a positional argument
                     # Do not pop if it is a Placeholder
-                    #   and change kind to positional only
+                    #   also change kind to positional only
+                    #   and remove default
                     if arg_value is functools.Placeholder:
-                        new_param = param.replace(kind=_POSITIONAL_ONLY)
+                        new_param = param.replace(
+                            kind=_POSITIONAL_ONLY,
+                            default=_empty
+                        )
                         new_params[param_name] = new_param
                     else:
                         new_params.pop(param_name)

Lib/test/test_functools.py

@@ -242,6 +242,12 @@ def test_placeholders_optimization(self):
         got, empty = p3(5)
         expected = (-1, 0, 1, 2, 3, 4, 5)
         self.assertTrue(expected == got and empty == {})
+        # inner partial has placeholders and outer partial has no args case
+        p = self.partial(capture, PH, 0)
+        p2 = self.partial(p)
+        expected = (PH, 0)
+        self.assertTrue(expected == p2.args)
+        self.assertTrue(((1, 0), {}) == p2(1))
 
     def test_construct_placeholder_singleton(self):
         PH = self.module.Placeholder
@@ -550,7 +556,7 @@ class TestPartialPySubclass(TestPartialPy):
     def test_subclass_optimization(self):
         p = py_functools.partial(min, 2)
         p2 = self.partial(p, 1)
-        assert p2.func == min
+        assert p2.func is min
         assert p2(0) == 0
 
 
@@ -696,7 +702,7 @@ class PartialMethodSubclass(functools.partialmethod):
             pass
         p = functools.partialmethod(min, 2)
         p2 = PartialMethodSubclass(p, 1)
-        assert p2.func == min
+        assert p2.func is min
         assert p2.__get__(0)() == 0
 
 

Lib/test/test_inspect/test_inspect.py

@@ -3523,16 +3523,16 @@ def foo(a=0, b=1, /, c=2, d=3):
         # Positional
         p = partial(foo, Placeholder, 1, c=0, d=1)
         self.assertEqual(self.signature(p),
-                         ((('a', 0, ..., "positional_only"),
+                         ((('a', ..., ..., "positional_only"),
                            ('c', 0, ..., "keyword_only"),
                            ('d', 1, ..., "keyword_only")),
                           ...))
 
         # Positional or Keyword - transformed to positional
         p = partial(foo, Placeholder, 1, Placeholder, 1)
         self.assertEqual(self.signature(p),
-                         ((('a', 0, ..., "positional_only"),
-                           ('c', 2, ..., "positional_only")),
+                         ((('a', ..., ..., "positional_only"),
+                           ('c', ..., ..., "positional_only")),
                           ...))
 
     def test_signature_on_partialmethod(self):

Modules/_functoolsmodule.c

@@ -656,12 +656,6 @@ partial_setstate(partialobject *pto, PyObject *state)
         PyErr_SetString(PyExc_TypeError, "invalid partial state");
         return NULL;
     }
-    Py_ssize_t state_len = PyTuple_GET_SIZE(state);
-    if (state_len != 4) {
-        PyErr_Format(PyExc_TypeError,
-                     "expected 4 items in state, got %zd", state_len);
-        return NULL;
-    }
     if (!PyArg_ParseTuple(state, "OOOO", &fn, &fnargs, &kw, &dict) ||
         !PyCallable_Check(fn) ||
         !PyTuple_Check(fnargs) ||