bpo-38787: C API for module state access from extension methods (PEP 573) (GH-19936)

Module C state is now accessible from C-defined heap type methods (PEP 573).
Patch by Marcel Plch and Petr Viktorin.

Co-authored-by: Marcel Plch <mplch@redhat.com>
Co-authored-by: Victor Stinner <vstinner@python.org>

1 files changed, 58 insertions, 6 deletions

diff --git a/Tools/clinic/clinic.py b/Tools/clinic/clinic.py
index 382e29a..281a749 100755
--- a/Tools/clinic/clinic.py
+++ b/Tools/clinic/clinic.py
@@ -657,9 +657,14 @@ class CLanguage(Language):
                 if not p.is_optional():
                     min_pos = i
 
+        requires_defining_class = any(
+            isinstance(p.converter, defining_class_converter)
+            for p in parameters)
+
         meth_o = (len(parameters) == 1 and
               parameters[0].is_positional_only() and
               not converters[0].is_optional() and
+              not requires_defining_class and
               not new_or_init)
 
         # we have to set these things before we're done:
@@ -717,6 +722,11 @@ class CLanguage(Language):
             {c_basename}({self_type}{self_name}, PyObject *const *args, Py_ssize_t nargs, PyObject *kwnames)
             """)
 
+        parser_prototype_def_class = normalize_snippet("""
+            static PyObject *
+            {c_basename}({self_type}{self_name}, PyTypeObject *cls, PyObject *const *args, Py_ssize_t nargs, PyObject *kwnames)
+        """)
+
         # parser_body_fields remembers the fields passed in to the
         # previous call to parser_body. this is used for an awful hack.
         parser_body_fields = ()
@@ -824,7 +834,7 @@ class CLanguage(Language):
 
             parser_definition = parser_body(parser_prototype, '    {option_group_parsing}')
 
-        elif pos_only == len(parameters):
+        elif not requires_defining_class and pos_only == len(parameters):
             if not new_or_init:
                 # positional-only, but no option groups
                 # we only need one call to _PyArg_ParseStack
@@ -891,7 +901,7 @@ class CLanguage(Language):
                 parser_prototype = parser_prototype_fastcall_keywords
                 argname_fmt = 'args[%d]'
                 declarations = normalize_snippet("""
-                    static const char * const _keywords[] = {{{keywords}, NULL}};
+                    static const char * const _keywords[] = {{{keywords} NULL}};
                     static _PyArg_Parser _parser = {{NULL, _keywords, "{name}", 0}};
                     PyObject *argsbuf[%s];
                     """ % len(converters))
@@ -909,7 +919,7 @@ class CLanguage(Language):
                 parser_prototype = parser_prototype_keyword
                 argname_fmt = 'fastargs[%d]'
                 declarations = normalize_snippet("""
-                    static const char * const _keywords[] = {{{keywords}, NULL}};
+                    static const char * const _keywords[] = {{{keywords} NULL}};
                     static _PyArg_Parser _parser = {{NULL, _keywords, "{name}", 0}};
                     PyObject *argsbuf[%s];
                     PyObject * const *fastargs;
@@ -923,6 +933,9 @@ class CLanguage(Language):
                         goto exit;
                     }}
                     """ % (min_pos, max_pos, min_kw_only), indent=4)]
+            if requires_defining_class:
+                flags = 'METH_METHOD|' + flags
+                parser_prototype = parser_prototype_def_class
 
             add_label = None
             for i, p in enumerate(parameters):
@@ -983,11 +996,11 @@ class CLanguage(Language):
                     parser_code.append("%s:" % add_label)
             else:
                 declarations = (
-                    'static const char * const _keywords[] = {{{keywords}, NULL}};\n'
+                    'static const char * const _keywords[] = {{{keywords} NULL}};\n'
                     'static _PyArg_Parser _parser = {{"{format_units}:{name}", _keywords, 0}};')
                 if not new_or_init:
                     parser_code = [normalize_snippet("""
-                        if (!_PyArg_ParseStackAndKeywords(args, nargs, kwnames, &_parser,
+                        if (!_PyArg_ParseStackAndKeywords(args, nargs, kwnames, &_parser{parse_arguments_comma}
                             {parse_arguments})) {{
                             goto exit;
                         }}
@@ -1021,6 +1034,9 @@ class CLanguage(Language):
             if parses_keywords:
                 assert parses_positional
 
+            if requires_defining_class:
+                raise ValueError("Slot methods cannot access their defining class.")
+
             if not parses_keywords:
                 fields.insert(0, normalize_snippet("""
                     if ({self_type_check}!_PyArg_NoKeywords("{name}", kwargs)) {{
@@ -1297,9 +1313,13 @@ class CLanguage(Language):
         template_dict['declarations'] = format_escape("\n".join(data.declarations))
         template_dict['initializers'] = "\n\n".join(data.initializers)
         template_dict['modifications'] = '\n\n'.join(data.modifications)
-        template_dict['keywords'] = '"' + '", "'.join(data.keywords) + '"'
+        template_dict['keywords'] = ' '.join('"' + k + '",' for k in data.keywords)
         template_dict['format_units'] = ''.join(data.format_units)
         template_dict['parse_arguments'] = ', '.join(data.parse_arguments)
+        if data.parse_arguments:
+            template_dict['parse_arguments_comma'] = ',';
+        else:
+            template_dict['parse_arguments_comma'] = '';
         template_dict['impl_parameters'] = ", ".join(data.impl_parameters)
         template_dict['impl_arguments'] = ", ".join(data.impl_arguments)
         template_dict['return_conversion'] = format_escape("".join(data.return_conversion).rstrip())
@@ -2730,6 +2750,25 @@ class bool_converter(CConverter):
                 """.format(argname=argname, paramname=self.name)
         return super().parse_arg(argname, displayname)
 
+class defining_class_converter(CConverter):
+    """
+    A special-case converter:
+    this is the default converter used for the defining class.
+    """
+    type = 'PyTypeObject *'
+    format_unit = ''
+    show_in_signature = False
+
+    def converter_init(self, *, type=None):
+        self.specified_type = type
+
+    def render(self, parameter, data):
+        self._render_self(parameter, data)
+
+    def set_template_dict(self, template_dict):
+        template_dict['defining_class_name'] = self.name
+
+
 class char_converter(CConverter):
     type = 'char'
     default_type = (bytes, bytearray)
@@ -4508,6 +4547,19 @@ class DSLParser:
             else:
                 fail("A 'self' parameter, if specified, must be the very first thing in the parameter block.")
 
+        if isinstance(converter, defining_class_converter):
+            _lp = len(self.function.parameters)
+            if _lp == 1:
+                if (self.parameter_state != self.ps_required):
+                    fail("A 'defining_class' parameter cannot be marked optional.")
+                if value is not unspecified:
+                    fail("A 'defining_class' parameter cannot have a default value.")
+                if self.group:
+                    fail("A 'defining_class' parameter cannot be in an optional group.")
+            else:
+                fail("A 'defining_class' parameter, if specified, must either be the first thing in the parameter block, or come just after 'self'.")
+
+
         p = Parameter(parameter_name, kind, function=self.function, converter=converter, default=value, group=self.group)
 
         if parameter_name in self.function.parameters: