posonly_optimization: address review feedback

Cython/Compiler/Nodes.py

@@ -3692,8 +3692,6 @@ class DefNodeWrapper(FuncDefNode):
         code.putln('{')
         all_args = tuple(positional_args) + tuple(kw_only_args)
         non_posonly_args = [arg for arg in all_args if not arg.pos_only]
-        do_generate_kw_unpacking = bool(non_posonly_args) or self.starstar_arg
-        if do_generate_kw_unpacking:
         code.putln("static PyObject **%s[] = {%s};" % (
             Naming.pykwdlist_cname,
             ','.join(['&%s' % code.intern_identifier(arg.name)
@@ -3709,18 +3707,41 @@ class DefNodeWrapper(FuncDefNode):
         # was passed for them.
         self.generate_argument_values_setup_code(all_args, code)
 
+        # If all args are positional-only, we can raise an error
+        # straight away if we receive a non-empty kw-dict.
+        # This requires a PyDict_Size call.  This call is wasteful
+        # for functions which do accept kw-args, so we do not generate
+        # the PyDict_Size call unless all args are positional-only.
+        accept_kwd_args = non_posonly_args or self.starstar_arg
+        if accept_kwd_args:
+            kw_unpacking_condition = Naming.kwds_cname
+        else:
+            kw_unpacking_condition = "%s && PyDict_Size(%s) > 0" % (
+                Naming.kwds_cname, Naming.kwds_cname)
+
         # --- optimised code when we receive keyword arguments
         code.putln("if (%s(%s)) {" % (
             (self.num_required_kw_args > 0) and "likely" or "unlikely",
-            Naming.kwds_cname))
+            kw_unpacking_condition))
 
-        if do_generate_kw_unpacking:
+        if accept_kwd_args:
             self.generate_keyword_unpacking_code(
                 min_positional_args, max_positional_args,
                 has_fixed_positional_count, has_kw_only_args, all_args, argtuple_error_label, code)
         else:
-            code.putln("PyErr_Format(PyExc_TypeError, \"%s() takes no keyword arguments\");" % self.name)
-            code.putln(code.error_goto(self.pos))
+            # Here we do not accept kw-args but we are passed a non-empty kw-dict.
+            # We call ParseOptionalKeywords which will raise an appropriate error if
+            # the kw-args dict passed is non-empty.
+            code.globalstate.use_utility_code(
+                UtilityCode.load_cached("ParseKeywords", "FunctionArguments.c"))
+            code.putln('if (unlikely(__Pyx_ParseOptionalKeywords(%s, %s, %s, %s, %s, "%s") < 0)) %s' % (
+                Naming.kwds_cname,
+                Naming.pykwdlist_cname,
+                self.starstar_arg and self.starstar_arg.entry.cname or '0',
+                'values',
+                0,
+                self.name,
+                code.error_goto(self.pos)))
 
         # --- optimised code when we do not receive any keyword arguments
         if (self.num_required_kw_args and min_positional_args > 0) or min_positional_args == max_positional_args:
@@ -3899,25 +3920,27 @@ class DefNodeWrapper(FuncDefNode):
         code.putln('switch (pos_args) {')
         if self.star_arg:
             code.putln('default:')
-        for i in range(max_positional_args-1, -1, -1):
+
+        for i in range(max_positional_args-1, num_required_posonly_args-1, -1):
             code.put('case %2d: ' % (i+1))
-            if i+1 > num_required_posonly_args:
             code.putln("values[%d] = PyTuple_GET_ITEM(%s, %d);" % (
                 i, Naming.args_cname, i))
             code.putln('CYTHON_FALLTHROUGH;')
-            elif i+1 == num_required_posonly_args:
-                for j in range(num_required_posonly_args-1, -1, -1):
+        if num_required_posonly_args > 0:
+            code.put('case %2d: ' % num_required_posonly_args)
+            for i in range(num_required_posonly_args-1, -1, -1):
                 code.putln("values[%d] = PyTuple_GET_ITEM(%s, %d);" % (
-                        j, Naming.args_cname, j))
+                    i, Naming.args_cname, i))
             code.putln('break;')
-            else:
+        for i in range(num_required_posonly_args-2, -1, -1):
+            code.put('case %2d: ' % (i+1))
             code.putln('CYTHON_FALLTHROUGH;')
 
+        code.put('case  0: ')
         if num_required_posonly_args == 0:
-            code.putln('case  0: break;')
+            code.putln('break;')
         else:
             # catch-all for not enough pos-only args passed
-            code.putln('case  0:')
             code.put_goto(argtuple_error_label)
         if not self.star_arg:
             code.put('default: ') # more arguments than allowed
@@ -3943,9 +3966,7 @@ class DefNodeWrapper(FuncDefNode):
                 last_required_arg = max_positional_args-1
             if max_positional_args > num_posonly_args:
                 code.putln('switch (pos_args) {')
-            for i, arg in enumerate(all_args[:last_required_arg+1]):
-                if i < num_posonly_args:
-                    continue
+            for i, arg in enumerate(all_args[num_posonly_args:last_required_arg+1], num_posonly_args):
                 if max_positional_args > num_posonly_args and i <= max_positional_args:
                     if i != num_posonly_args:
                         code.putln('CYTHON_FALLTHROUGH;')

tests/run/posonly.pyx

@@ -2,8 +2,6 @@
 # mode: run
 # tag: posonly
 
-# TODO: remove posonly tag before merge
-
 import cython
 import sys
 import pickle
@@ -126,7 +124,7 @@ def test_use_positional_as_keyword3(a, b, /):
     >>> test_use_positional_as_keyword3(1, 2)
     >>> test_use_positional_as_keyword3(a=1, b=2)
     Traceback (most recent call last):
-    TypeError: test_use_positional_as_keyword3() takes no keyword arguments
+    TypeError: test_use_positional_as_keyword3() got an unexpected keyword argument 'a'
     """
 
 def test_positional_only_and_arg_invalid_calls(a, b, /, c):
@@ -266,7 +264,7 @@ class TestPosonlyMethods(object):
     Got type error
     >>> TestPosonlyMethods().f(1, b=2)
     Traceback (most recent call last):
-    TypeError: f() takes no keyword arguments
+    TypeError: f() got an unexpected keyword argument 'b'
     """
     def f(self, a, b, /):
         return a, b
@@ -367,7 +365,7 @@ def test_serialization1(a, b, /):
     (1, 2)
     >>> unpickled_posonly(a=1, b=2)
     Traceback (most recent call last):
-    TypeError: test_serialization1() takes no keyword arguments
+    TypeError: test_serialization1() got an unexpected keyword argument 'a'
     """
     return (a, b)
 
@@ -510,7 +508,8 @@ def f_call_posonly_kwarg(a,/,**kw):
     """
     >>> f_call_posonly_kwarg(1)
     (1, {})
-    >>> f_call_posonly_kwarg(1, b=2, c=3, d=4)==(1, {'b': 2, 'c': 3, 'd': 4})
+    >>> all_args = f_call_posonly_kwarg(1, b=2, c=3, d=4)
+    >>> all_args == (1, {'b': 2, 'c': 3, 'd': 4}) or all_args
     True
     """
     return (a,kw)
@@ -521,9 +520,23 @@ def f_call_posonly_stararg_kwarg(a,/,*args,**kw):
     (1, (), {})
     >>> f_call_posonly_stararg_kwarg(1, 2)
     (1, (2,), {})
-    >>> f_call_posonly_stararg_kwarg(1, b=3, c=4)==(1, (), {'b': 3, 'c': 4})
+    >>> all_args = f_call_posonly_stararg_kwarg(1, b=3, c=4)
+    >>> all_args == (1, (), {'b': 3, 'c': 4}) or all_args
     True
-    >>> f_call_posonly_stararg_kwarg(1, 2, b=3, c=4)==(1, (2,), {'b': 3, 'c': 4})
+    >>> all_args = f_call_posonly_stararg_kwarg(1, 2, b=3, c=4)
+    >>> all_args == (1, (2,), {'b': 3, 'c': 4}) or all_args
     True
     """
     return (a,args,kw)
+
+def test_empty_kwargs(a, b, /):
+    """
+    >>> test_empty_kwargs(1, 2)
+    (1, 2)
+    >>> test_empty_kwargs(1, 2, **{})
+    (1, 2)
+    >>> test_empty_kwargs(1, 2, **{'c': 3})
+    Traceback (most recent call last):
+    TypeError: test_empty_kwargs() got an unexpected keyword argument 'c'
+    """
+    return (a,b)