gh-113317, AC: Add libclinic.converter module (#116821)

* Move CConverter class to a new libclinic.converter module.
* Move CRenderData and Include classes to a new libclinic.crenderdata
  module.

4 files changed, 621 insertions, 601 deletions

diff --git a/Tools/clinic/clinic.py b/Tools/clinic/clinic.py
index ac20586..c9641cb 100755
--- a/Tools/clinic/clinic.py
+++ b/Tools/clinic/clinic.py
@@ -32,15 +32,12 @@ from collections.abc import (
 from operator import attrgetter
 from types import FunctionType, NoneType
 from typing import (
-    TYPE_CHECKING,
     Any,
     Final,
     Literal,
     NamedTuple,
     NoReturn,
     Protocol,
-    TypeVar,
-    cast,
 )
 
 
@@ -57,6 +54,10 @@ from libclinic.function import (
     GETTER, SETTER)
 from libclinic.language import Language, PythonLanguage
 from libclinic.block_parser import Block, BlockParser
+from libclinic.crenderdata import CRenderData, Include, TemplateDict
+from libclinic.converter import (
+    CConverter, CConverterClassT,
+    converters, legacy_converters)
 
 
 # TODO:
@@ -84,65 +85,6 @@ class Null:
 
 NULL = Null()
 
-TemplateDict = dict[str, str]
-
-
-class CRenderData:
-    def __init__(self) -> None:
-
-        # The C statements to declare variables.
-        # Should be full lines with \n eol characters.
-        self.declarations: list[str] = []
-
-        # The C statements required to initialize the variables before the parse call.
-        # Should be full lines with \n eol characters.
-        self.initializers: list[str] = []
-
-        # The C statements needed to dynamically modify the values
-        # parsed by the parse call, before calling the impl.
-        self.modifications: list[str] = []
-
-        # The entries for the "keywords" array for PyArg_ParseTuple.
-        # Should be individual strings representing the names.
-        self.keywords: list[str] = []
-
-        # The "format units" for PyArg_ParseTuple.
-        # Should be individual strings that will get
-        self.format_units: list[str] = []
-
-        # The varargs arguments for PyArg_ParseTuple.
-        self.parse_arguments: list[str] = []
-
-        # The parameter declarations for the impl function.
-        self.impl_parameters: list[str] = []
-
-        # The arguments to the impl function at the time it's called.
-        self.impl_arguments: list[str] = []
-
-        # For return converters: the name of the variable that
-        # should receive the value returned by the impl.
-        self.return_value = "return_value"
-
-        # For return converters: the code to convert the return
-        # value from the parse function.  This is also where
-        # you should check the _return_value for errors, and
-        # "goto exit" if there are any.
-        self.return_conversion: list[str] = []
-        self.converter_retval = "_return_value"
-
-        # The C statements required to do some operations
-        # after the end of parsing but before cleaning up.
-        # These operations may be, for example, memory deallocations which
-        # can only be done without any error happening during argument parsing.
-        self.post_parsing: list[str] = []
-
-        # The C statements required to clean up after the impl call.
-        self.cleanup: list[str] = []
-
-        # The C statements to generate critical sections (per-object locking).
-        self.lock: list[str] = []
-        self.unlock: list[str] = []
-
 
 ParamTuple = tuple["Parameter", ...]
 
@@ -1556,26 +1498,6 @@ class CLanguage(Language):
         return clinic.get_destination('block').dump()
 
 
-@dc.dataclass(slots=True, frozen=True)
-class Include:
-    """
-    An include like: #include "pycore_long.h"   // _Py_ID()
-    """
-    # Example: "pycore_long.h".
-    filename: str
-
-    # Example: "_Py_ID()".
-    reason: str
-
-    # None means unconditional include.
-    # Example: "#if defined(Py_BUILD_CORE) && !defined(Py_BUILD_CORE_MODULE)".
-    condition: str | None
-
-    def sort_key(self) -> tuple[str, str]:
-        # order: '#if' comes before 'NO_CONDITION'
-        return (self.condition or 'NO_CONDITION', self.filename)
-
-
 @dc.dataclass(slots=True)
 class BlockPrinter:
     language: Language
@@ -2151,29 +2073,6 @@ __xor__
 ReturnConverterType = Callable[..., "CReturnConverter"]
 
 
-CConverterClassT = TypeVar("CConverterClassT", bound=type["CConverter"])
-
-def add_c_converter(
-        f: CConverterClassT,
-        name: str | None = None
-) -> CConverterClassT:
-    if not name:
-        name = f.__name__
-        if not name.endswith('_converter'):
-            return f
-        name = name.removesuffix('_converter')
-    converters[name] = f
-    return f
-
-def add_default_legacy_c_converter(cls: CConverterClassT) -> CConverterClassT:
-    # automatically add converter for default format unit
-    # (but without stomping on the existing one if it's already
-    # set, in case you subclass)
-    if ((cls.format_unit not in ('O&', '')) and
-        (cls.format_unit not in legacy_converters)):
-        legacy_converters[cls.format_unit] = cls
-    return cls
-
 def add_legacy_c_converter(
         format_unit: str,
         **kwargs: Any
@@ -2192,501 +2091,6 @@ def add_legacy_c_converter(
         return f
     return closure
 
-class CConverterAutoRegister(type):
-    def __init__(
-        cls, name: str, bases: tuple[type[object], ...], classdict: dict[str, Any]
-    ) -> None:
-        converter_cls = cast(type["CConverter"], cls)
-        add_c_converter(converter_cls)
-        add_default_legacy_c_converter(converter_cls)
-
-class CConverter(metaclass=CConverterAutoRegister):
-    """
-    For the init function, self, name, function, and default
-    must be keyword-or-positional parameters.  All other
-    parameters must be keyword-only.
-    """
-
-    # The C name to use for this variable.
-    name: str
-
-    # The Python name to use for this variable.
-    py_name: str
-
-    # The C type to use for this variable.
-    # 'type' should be a Python string specifying the type, e.g. "int".
-    # If this is a pointer type, the type string should end with ' *'.
-    type: str | None = None
-
-    # The Python default value for this parameter, as a Python value.
-    # Or the magic value "unspecified" if there is no default.
-    # Or the magic value "unknown" if this value is a cannot be evaluated
-    # at Argument-Clinic-preprocessing time (but is presumed to be valid
-    # at runtime).
-    default: object = unspecified
-
-    # If not None, default must be isinstance() of this type.
-    # (You can also specify a tuple of types.)
-    default_type: bltns.type[object] | tuple[bltns.type[object], ...] | None = None
-
-    # "default" converted into a C value, as a string.
-    # Or None if there is no default.
-    c_default: str | None = None
-
-    # "default" converted into a Python value, as a string.
-    # Or None if there is no default.
-    py_default: str | None = None
-
-    # The default value used to initialize the C variable when
-    # there is no default, but not specifying a default may
-    # result in an "uninitialized variable" warning.  This can
-    # easily happen when using option groups--although
-    # properly-written code won't actually use the variable,
-    # the variable does get passed in to the _impl.  (Ah, if
-    # only dataflow analysis could inline the static function!)
-    #
-    # This value is specified as a string.
-    # Every non-abstract subclass should supply a valid value.
-    c_ignored_default: str = 'NULL'
-
-    # If true, wrap with Py_UNUSED.
-    unused = False
-
-    # The C converter *function* to be used, if any.
-    # (If this is not None, format_unit must be 'O&'.)
-    converter: str | None = None
-
-    # Should Argument Clinic add a '&' before the name of
-    # the variable when passing it into the _impl function?
-    impl_by_reference = False
-
-    # Should Argument Clinic add a '&' before the name of
-    # the variable when passing it into PyArg_ParseTuple (AndKeywords)?
-    parse_by_reference = True
-
-    #############################################################
-    #############################################################
-    ## You shouldn't need to read anything below this point to ##
-    ## write your own converter functions.                     ##
-    #############################################################
-    #############################################################
-
-    # The "format unit" to specify for this variable when
-    # parsing arguments using PyArg_ParseTuple (AndKeywords).
-    # Custom converters should always use the default value of 'O&'.
-    format_unit = 'O&'
-
-    # What encoding do we want for this variable?  Only used
-    # by format units starting with 'e'.
-    encoding: str | None = None
-
-    # Should this object be required to be a subclass of a specific type?
-    # If not None, should be a string representing a pointer to a
-    # PyTypeObject (e.g. "&PyUnicode_Type").
-    # Only used by the 'O!' format unit (and the "object" converter).
-    subclass_of: str | None = None
-
-    # See also the 'length_name' property.
-    # Only used by format units ending with '#'.
-    length = False
-
-    # Should we show this parameter in the generated
-    # __text_signature__? This is *almost* always True.
-    # (It's only False for __new__, __init__, and METH_STATIC functions.)
-    show_in_signature = True
-
-    # Overrides the name used in a text signature.
-    # The name used for a "self" parameter must be one of
-    # self, type, or module; however users can set their own.
-    # This lets the self_converter overrule the user-settable
-    # name, *just* for the text signature.
-    # Only set by self_converter.
-    signature_name: str | None = None
-
-    broken_limited_capi: bool = False
-
-    # keep in sync with self_converter.__init__!
-    def __init__(self,
-             # Positional args:
-             name: str,
-             py_name: str,
-             function: Function,
-             default: object = unspecified,
-             *,  # Keyword only args:
-             c_default: str | None = None,
-             py_default: str | None = None,
-             annotation: str | Literal[Sentinels.unspecified] = unspecified,
-             unused: bool = False,
-             **kwargs: Any
-    ) -> None:
-        self.name = libclinic.ensure_legal_c_identifier(name)
-        self.py_name = py_name
-        self.unused = unused
-        self.includes: list[Include] = []
-
-        if default is not unspecified:
-            if (self.default_type
-                and default is not unknown
-                and not isinstance(default, self.default_type)
-            ):
-                if isinstance(self.default_type, type):
-                    types_str = self.default_type.__name__
-                else:
-                    names = [cls.__name__ for cls in self.default_type]
-                    types_str = ', '.join(names)
-                cls_name = self.__class__.__name__
-                fail(f"{cls_name}: default value {default!r} for field "
-                     f"{name!r} is not of type {types_str!r}")
-            self.default = default
-
-        if c_default:
-            self.c_default = c_default
-        if py_default:
-            self.py_default = py_default
-
-        if annotation is not unspecified:
-            fail("The 'annotation' parameter is not currently permitted.")
-
-        # Make sure not to set self.function until after converter_init() has been called.
-        # This prevents you from caching information
-        # about the function in converter_init().
-        # (That breaks if we get cloned.)
-        self.converter_init(**kwargs)
-        self.function = function
-
-    # Add a custom __getattr__ method to improve the error message
-    # if somebody tries to access self.function in converter_init().
-    #
-    # mypy will assume arbitrary access is okay for a class with a __getattr__ method,
-    # and that's not what we want,
-    # so put it inside an `if not TYPE_CHECKING` block
-    if not TYPE_CHECKING:
-        def __getattr__(self, attr):
-            if attr == "function":
-                fail(
-                    f"{self.__class__.__name__!r} object has no attribute 'function'.\n"
-                    f"Note: accessing self.function inside converter_init is disallowed!"
-                )
-            return super().__getattr__(attr)
-    # this branch is just here for coverage reporting
-    else:  # pragma: no cover
-        pass
-
-    def converter_init(self) -> None:
-        pass
-
-    def is_optional(self) -> bool:
-        return (self.default is not unspecified)
-
-    def _render_self(self, parameter: Parameter, data: CRenderData) -> None:
-        self.parameter = parameter
-        name = self.parser_name
-
-        # impl_arguments
-        s = ("&" if self.impl_by_reference else "") + name
-        data.impl_arguments.append(s)
-        if self.length:
-            data.impl_arguments.append(self.length_name)
-
-        # impl_parameters
-        data.impl_parameters.append(self.simple_declaration(by_reference=self.impl_by_reference))
-        if self.length:
-            data.impl_parameters.append(f"Py_ssize_t {self.length_name}")
-
-    def _render_non_self(
-            self,
-            parameter: Parameter,
-            data: CRenderData
-    ) -> None:
-        self.parameter = parameter
-        name = self.name
-
-        # declarations
-        d = self.declaration(in_parser=True)
-        data.declarations.append(d)
-
-        # initializers
-        initializers = self.initialize()
-        if initializers:
-            data.initializers.append('/* initializers for ' + name + ' */\n' + initializers.rstrip())
-
-        # modifications
-        modifications = self.modify()
-        if modifications:
-            data.modifications.append('/* modifications for ' + name + ' */\n' + modifications.rstrip())
-
-        # keywords
-        if parameter.is_vararg():
-            pass
-        elif parameter.is_positional_only():
-            data.keywords.append('')
-        else:
-            data.keywords.append(parameter.name)
-
-        # format_units
-        if self.is_optional() and '|' not in data.format_units:
-            data.format_units.append('|')
-        if parameter.is_keyword_only() and '$' not in data.format_units:
-            data.format_units.append('$')
-        data.format_units.append(self.format_unit)
-
-        # parse_arguments
-        self.parse_argument(data.parse_arguments)
-
-        # post_parsing
-        if post_parsing := self.post_parsing():
-            data.post_parsing.append('/* Post parse cleanup for ' + name + ' */\n' + post_parsing.rstrip() + '\n')
-
-        # cleanup
-        cleanup = self.cleanup()
-        if cleanup:
-            data.cleanup.append('/* Cleanup for ' + name + ' */\n' + cleanup.rstrip() + "\n")
-
-    def render(self, parameter: Parameter, data: CRenderData) -> None:
-        """
-        parameter is a clinic.Parameter instance.
-        data is a CRenderData instance.
-        """
-        self._render_self(parameter, data)
-        self._render_non_self(parameter, data)
-
-    @functools.cached_property
-    def length_name(self) -> str:
-        """Computes the name of the associated "length" variable."""
-        assert self.length is not None
-        return self.parser_name + "_length"
-
-    # Why is this one broken out separately?
-    # For "positional-only" function parsing,
-    # which generates a bunch of PyArg_ParseTuple calls.
-    def parse_argument(self, args: list[str]) -> None:
-        assert not (self.converter and self.encoding)
-        if self.format_unit == 'O&':
-            assert self.converter
-            args.append(self.converter)
-
-        if self.encoding:
-            args.append(libclinic.c_repr(self.encoding))
-        elif self.subclass_of:
-            args.append(self.subclass_of)
-
-        s = ("&" if self.parse_by_reference else "") + self.parser_name
-        args.append(s)
-
-        if self.length:
-            args.append(f"&{self.length_name}")
-
-    #
-    # All the functions after here are intended as extension points.
-    #
-
-    def simple_declaration(
-            self,
-            by_reference: bool = False,
-            *,
-            in_parser: bool = False
-    ) -> str:
-        """
-        Computes the basic declaration of the variable.
-        Used in computing the prototype declaration and the
-        variable declaration.
-        """
-        assert isinstance(self.type, str)
-        prototype = [self.type]
-        if by_reference or not self.type.endswith('*'):
-            prototype.append(" ")
-        if by_reference:
-            prototype.append('*')
-        if in_parser:
-            name = self.parser_name
-        else:
-            name = self.name
-            if self.unused:
-                name = f"Py_UNUSED({name})"
-        prototype.append(name)
-        return "".join(prototype)
-
-    def declaration(self, *, in_parser: bool = False) -> str:
-        """
-        The C statement to declare this variable.
-        """
-        declaration = [self.simple_declaration(in_parser=True)]
-        default = self.c_default
-        if not default and self.parameter.group:
-            default = self.c_ignored_default
-        if default:
-            declaration.append(" = ")
-            declaration.append(default)
-        declaration.append(";")
-        if self.length:
-            declaration.append('\n')
-            declaration.append(f"Py_ssize_t {self.length_name};")
-        return "".join(declaration)
-
-    def initialize(self) -> str:
-        """
-        The C statements required to set up this variable before parsing.
-        Returns a string containing this code indented at column 0.
-        If no initialization is necessary, returns an empty string.
-        """
-        return ""
-
-    def modify(self) -> str:
-        """
-        The C statements required to modify this variable after parsing.
-        Returns a string containing this code indented at column 0.
-        If no modification is necessary, returns an empty string.
-        """
-        return ""
-
-    def post_parsing(self) -> str:
-        """
-        The C statements required to do some operations after the end of parsing but before cleaning up.
-        Return a string containing this code indented at column 0.
-        If no operation is necessary, return an empty string.
-        """
-        return ""
-
-    def cleanup(self) -> str:
-        """
-        The C statements required to clean up after this variable.
-        Returns a string containing this code indented at column 0.
-        If no cleanup is necessary, returns an empty string.
-        """
-        return ""
-
-    def pre_render(self) -> None:
-        """
-        A second initialization function, like converter_init,
-        called just before rendering.
-        You are permitted to examine self.function here.
-        """
-        pass
-
-    def bad_argument(self, displayname: str, expected: str, *, limited_capi: bool, expected_literal: bool = True) -> str:
-        assert '"' not in expected
-        if limited_capi:
-            if expected_literal:
-                return (f'PyErr_Format(PyExc_TypeError, '
-                        f'"{{{{name}}}}() {displayname} must be {expected}, not %.50s", '
-                        f'{{argname}} == Py_None ? "None" : Py_TYPE({{argname}})->tp_name);')
-            else:
-                return (f'PyErr_Format(PyExc_TypeError, '
-                        f'"{{{{name}}}}() {displayname} must be %.50s, not %.50s", '
-                        f'"{expected}", '
-                        f'{{argname}} == Py_None ? "None" : Py_TYPE({{argname}})->tp_name);')
-        else:
-            if expected_literal:
-                expected = f'"{expected}"'
-            self.add_include('pycore_modsupport.h', '_PyArg_BadArgument()')
-            return f'_PyArg_BadArgument("{{{{name}}}}", "{displayname}", {expected}, {{argname}});'
-
-    def format_code(self, fmt: str, *,
-                    argname: str,
-                    bad_argument: str | None = None,
-                    bad_argument2: str | None = None,
-                    **kwargs: Any) -> str:
-        if '{bad_argument}' in fmt:
-            if not bad_argument:
-                raise TypeError("required 'bad_argument' argument")
-            fmt = fmt.replace('{bad_argument}', bad_argument)
-        if '{bad_argument2}' in fmt:
-            if not bad_argument2:
-                raise TypeError("required 'bad_argument2' argument")
-            fmt = fmt.replace('{bad_argument2}', bad_argument2)
-        return fmt.format(argname=argname, paramname=self.parser_name, **kwargs)
-
-    def use_converter(self) -> None:
-        """Method called when self.converter is used to parse an argument."""
-        pass
-
-    def parse_arg(self, argname: str, displayname: str, *, limited_capi: bool) -> str | None:
-        if self.format_unit == 'O&':
-            self.use_converter()
-            return self.format_code("""
-                if (!{converter}({argname}, &{paramname})) {{{{
-                    goto exit;
-                }}}}
-                """,
-                argname=argname,
-                converter=self.converter)
-        if self.format_unit == 'O!':
-            cast = '(%s)' % self.type if self.type != 'PyObject *' else ''
-            if self.subclass_of in type_checks:
-                typecheck, typename = type_checks[self.subclass_of]
-                return self.format_code("""
-                    if (!{typecheck}({argname})) {{{{
-                        {bad_argument}
-                        goto exit;
-                    }}}}
-                    {paramname} = {cast}{argname};
-                    """,
-                    argname=argname,
-                    bad_argument=self.bad_argument(displayname, typename, limited_capi=limited_capi),
-                    typecheck=typecheck, typename=typename, cast=cast)
-            return self.format_code("""
-                if (!PyObject_TypeCheck({argname}, {subclass_of})) {{{{
-                    {bad_argument}
-                    goto exit;
-                }}}}
-                {paramname} = {cast}{argname};
-                """,
-                argname=argname,
-                bad_argument=self.bad_argument(displayname, '({subclass_of})->tp_name',
-                                               expected_literal=False, limited_capi=limited_capi),
-                subclass_of=self.subclass_of, cast=cast)
-        if self.format_unit == 'O':
-            cast = '(%s)' % self.type if self.type != 'PyObject *' else ''
-            return self.format_code("""
-                {paramname} = {cast}{argname};
-                """,
-                argname=argname, cast=cast)
-        return None
-
-    def set_template_dict(self, template_dict: TemplateDict) -> None:
-        pass
-
-    @property
-    def parser_name(self) -> str:
-        if self.name in libclinic.CLINIC_PREFIXED_ARGS: # bpo-39741
-            return libclinic.CLINIC_PREFIX + self.name
-        else:
-            return self.name
-
-    def add_include(self, name: str, reason: str,
-                    *, condition: str | None = None) -> None:
-        include = Include(name, reason, condition)
-        self.includes.append(include)
-
-type_checks = {
-    '&PyLong_Type': ('PyLong_Check', 'int'),
-    '&PyTuple_Type': ('PyTuple_Check', 'tuple'),
-    '&PyList_Type': ('PyList_Check', 'list'),
-    '&PySet_Type': ('PySet_Check', 'set'),
-    '&PyFrozenSet_Type': ('PyFrozenSet_Check', 'frozenset'),
-    '&PyDict_Type': ('PyDict_Check', 'dict'),
-    '&PyUnicode_Type': ('PyUnicode_Check', 'str'),
-    '&PyBytes_Type': ('PyBytes_Check', 'bytes'),
-    '&PyByteArray_Type': ('PyByteArray_Check', 'bytearray'),
-}
-
-
-ConverterType = Callable[..., CConverter]
-ConverterDict = dict[str, ConverterType]
-
-# maps strings to callables.
-# these callables must be of the form:
-#   def foo(name, default, *, ...)
-# The callable may have any number of keyword-only parameters.
-# The callable must return a CConverter object.
-# The callable should not call builtins.print.
-converters: ConverterDict = {}
-
-# maps strings to callables.
-# these callables follow the same rules as those for "converters" above.
-# note however that they will never be called with keyword-only parameters.
-legacy_converters: ConverterDict = {}
-
 # maps strings to callables.
 # these callables must be of the form:
 #   def foo(*, ...)
diff --git a/Tools/clinic/libclinic/converter.py b/Tools/clinic/libclinic/converter.py
new file mode 100644
index 0000000..da28ba5
--- /dev/null
+++ b/Tools/clinic/libclinic/converter.py
@@ -0,0 +1,534 @@
+from __future__ import annotations
+import builtins as bltns
+import functools
+from typing import Any, TypeVar, Literal, TYPE_CHECKING, cast
+from collections.abc import Callable
+
+import libclinic
+from libclinic import fail
+from libclinic import Sentinels, unspecified, unknown
+from libclinic.crenderdata import CRenderData, Include, TemplateDict
+from libclinic.function import Function, Parameter
+
+
+CConverterClassT = TypeVar("CConverterClassT", bound=type["CConverter"])
+
+
+type_checks = {
+    '&PyLong_Type': ('PyLong_Check', 'int'),
+    '&PyTuple_Type': ('PyTuple_Check', 'tuple'),
+    '&PyList_Type': ('PyList_Check', 'list'),
+    '&PySet_Type': ('PySet_Check', 'set'),
+    '&PyFrozenSet_Type': ('PyFrozenSet_Check', 'frozenset'),
+    '&PyDict_Type': ('PyDict_Check', 'dict'),
+    '&PyUnicode_Type': ('PyUnicode_Check', 'str'),
+    '&PyBytes_Type': ('PyBytes_Check', 'bytes'),
+    '&PyByteArray_Type': ('PyByteArray_Check', 'bytearray'),
+}
+
+
+def add_c_converter(
+        f: CConverterClassT,
+        name: str | None = None
+) -> CConverterClassT:
+    if not name:
+        name = f.__name__
+        if not name.endswith('_converter'):
+            return f
+        name = name.removesuffix('_converter')
+    converters[name] = f
+    return f
+
+
+def add_default_legacy_c_converter(cls: CConverterClassT) -> CConverterClassT:
+    # automatically add converter for default format unit
+    # (but without stomping on the existing one if it's already
+    # set, in case you subclass)
+    if ((cls.format_unit not in ('O&', '')) and
+        (cls.format_unit not in legacy_converters)):
+        legacy_converters[cls.format_unit] = cls
+    return cls
+
+
+class CConverterAutoRegister(type):
+    def __init__(
+        cls, name: str, bases: tuple[type[object], ...], classdict: dict[str, Any]
+    ) -> None:
+        converter_cls = cast(type["CConverter"], cls)
+        add_c_converter(converter_cls)
+        add_default_legacy_c_converter(converter_cls)
+
+class CConverter(metaclass=CConverterAutoRegister):
+    """
+    For the init function, self, name, function, and default
+    must be keyword-or-positional parameters.  All other
+    parameters must be keyword-only.
+    """
+
+    # The C name to use for this variable.
+    name: str
+
+    # The Python name to use for this variable.
+    py_name: str
+
+    # The C type to use for this variable.
+    # 'type' should be a Python string specifying the type, e.g. "int".
+    # If this is a pointer type, the type string should end with ' *'.
+    type: str | None = None
+
+    # The Python default value for this parameter, as a Python value.
+    # Or the magic value "unspecified" if there is no default.
+    # Or the magic value "unknown" if this value is a cannot be evaluated
+    # at Argument-Clinic-preprocessing time (but is presumed to be valid
+    # at runtime).
+    default: object = unspecified
+
+    # If not None, default must be isinstance() of this type.
+    # (You can also specify a tuple of types.)
+    default_type: bltns.type[object] | tuple[bltns.type[object], ...] | None = None
+
+    # "default" converted into a C value, as a string.
+    # Or None if there is no default.
+    c_default: str | None = None
+
+    # "default" converted into a Python value, as a string.
+    # Or None if there is no default.
+    py_default: str | None = None
+
+    # The default value used to initialize the C variable when
+    # there is no default, but not specifying a default may
+    # result in an "uninitialized variable" warning.  This can
+    # easily happen when using option groups--although
+    # properly-written code won't actually use the variable,
+    # the variable does get passed in to the _impl.  (Ah, if
+    # only dataflow analysis could inline the static function!)
+    #
+    # This value is specified as a string.
+    # Every non-abstract subclass should supply a valid value.
+    c_ignored_default: str = 'NULL'
+
+    # If true, wrap with Py_UNUSED.
+    unused = False
+
+    # The C converter *function* to be used, if any.
+    # (If this is not None, format_unit must be 'O&'.)
+    converter: str | None = None
+
+    # Should Argument Clinic add a '&' before the name of
+    # the variable when passing it into the _impl function?
+    impl_by_reference = False
+
+    # Should Argument Clinic add a '&' before the name of
+    # the variable when passing it into PyArg_ParseTuple (AndKeywords)?
+    parse_by_reference = True
+
+    #############################################################
+    #############################################################
+    ## You shouldn't need to read anything below this point to ##
+    ## write your own converter functions.                     ##
+    #############################################################
+    #############################################################
+
+    # The "format unit" to specify for this variable when
+    # parsing arguments using PyArg_ParseTuple (AndKeywords).
+    # Custom converters should always use the default value of 'O&'.
+    format_unit = 'O&'
+
+    # What encoding do we want for this variable?  Only used
+    # by format units starting with 'e'.
+    encoding: str | None = None
+
+    # Should this object be required to be a subclass of a specific type?
+    # If not None, should be a string representing a pointer to a
+    # PyTypeObject (e.g. "&PyUnicode_Type").
+    # Only used by the 'O!' format unit (and the "object" converter).
+    subclass_of: str | None = None
+
+    # See also the 'length_name' property.
+    # Only used by format units ending with '#'.
+    length = False
+
+    # Should we show this parameter in the generated
+    # __text_signature__? This is *almost* always True.
+    # (It's only False for __new__, __init__, and METH_STATIC functions.)
+    show_in_signature = True
+
+    # Overrides the name used in a text signature.
+    # The name used for a "self" parameter must be one of
+    # self, type, or module; however users can set their own.
+    # This lets the self_converter overrule the user-settable
+    # name, *just* for the text signature.
+    # Only set by self_converter.
+    signature_name: str | None = None
+
+    broken_limited_capi: bool = False
+
+    # keep in sync with self_converter.__init__!
+    def __init__(self,
+             # Positional args:
+             name: str,
+             py_name: str,
+             function: Function,
+             default: object = unspecified,
+             *,  # Keyword only args:
+             c_default: str | None = None,
+             py_default: str | None = None,
+             annotation: str | Literal[Sentinels.unspecified] = unspecified,
+             unused: bool = False,
+             **kwargs: Any
+    ) -> None:
+        self.name = libclinic.ensure_legal_c_identifier(name)
+        self.py_name = py_name
+        self.unused = unused
+        self.includes: list[Include] = []
+
+        if default is not unspecified:
+            if (self.default_type
+                and default is not unknown
+                and not isinstance(default, self.default_type)
+            ):
+                if isinstance(self.default_type, type):
+                    types_str = self.default_type.__name__
+                else:
+                    names = [cls.__name__ for cls in self.default_type]
+                    types_str = ', '.join(names)
+                cls_name = self.__class__.__name__
+                fail(f"{cls_name}: default value {default!r} for field "
+                     f"{name!r} is not of type {types_str!r}")
+            self.default = default
+
+        if c_default:
+            self.c_default = c_default
+        if py_default:
+            self.py_default = py_default
+
+        if annotation is not unspecified:
+            fail("The 'annotation' parameter is not currently permitted.")
+
+        # Make sure not to set self.function until after converter_init() has been called.
+        # This prevents you from caching information
+        # about the function in converter_init().
+        # (That breaks if we get cloned.)
+        self.converter_init(**kwargs)
+        self.function = function
+
+    # Add a custom __getattr__ method to improve the error message
+    # if somebody tries to access self.function in converter_init().
+    #
+    # mypy will assume arbitrary access is okay for a class with a __getattr__ method,
+    # and that's not what we want,
+    # so put it inside an `if not TYPE_CHECKING` block
+    if not TYPE_CHECKING:
+        def __getattr__(self, attr):
+            if attr == "function":
+                fail(
+                    f"{self.__class__.__name__!r} object has no attribute 'function'.\n"
+                    f"Note: accessing self.function inside converter_init is disallowed!"
+                )
+            return super().__getattr__(attr)
+    # this branch is just here for coverage reporting
+    else:  # pragma: no cover
+        pass
+
+    def converter_init(self) -> None:
+        pass
+
+    def is_optional(self) -> bool:
+        return (self.default is not unspecified)
+
+    def _render_self(self, parameter: Parameter, data: CRenderData) -> None:
+        self.parameter = parameter
+        name = self.parser_name
+
+        # impl_arguments
+        s = ("&" if self.impl_by_reference else "") + name
+        data.impl_arguments.append(s)
+        if self.length:
+            data.impl_arguments.append(self.length_name)
+
+        # impl_parameters
+        data.impl_parameters.append(self.simple_declaration(by_reference=self.impl_by_reference))
+        if self.length:
+            data.impl_parameters.append(f"Py_ssize_t {self.length_name}")
+
+    def _render_non_self(
+            self,
+            parameter: Parameter,
+            data: CRenderData
+    ) -> None:
+        self.parameter = parameter
+        name = self.name
+
+        # declarations
+        d = self.declaration(in_parser=True)
+        data.declarations.append(d)
+
+        # initializers
+        initializers = self.initialize()
+        if initializers:
+            data.initializers.append('/* initializers for ' + name + ' */\n' + initializers.rstrip())
+
+        # modifications
+        modifications = self.modify()
+        if modifications:
+            data.modifications.append('/* modifications for ' + name + ' */\n' + modifications.rstrip())
+
+        # keywords
+        if parameter.is_vararg():
+            pass
+        elif parameter.is_positional_only():
+            data.keywords.append('')
+        else:
+            data.keywords.append(parameter.name)
+
+        # format_units
+        if self.is_optional() and '|' not in data.format_units:
+            data.format_units.append('|')
+        if parameter.is_keyword_only() and '$' not in data.format_units:
+            data.format_units.append('$')
+        data.format_units.append(self.format_unit)
+
+        # parse_arguments
+        self.parse_argument(data.parse_arguments)
+
+        # post_parsing
+        if post_parsing := self.post_parsing():
+            data.post_parsing.append('/* Post parse cleanup for ' + name + ' */\n' + post_parsing.rstrip() + '\n')
+
+        # cleanup
+        cleanup = self.cleanup()
+        if cleanup:
+            data.cleanup.append('/* Cleanup for ' + name + ' */\n' + cleanup.rstrip() + "\n")
+
+    def render(self, parameter: Parameter, data: CRenderData) -> None:
+        """
+        parameter is a clinic.Parameter instance.
+        data is a CRenderData instance.
+        """
+        self._render_self(parameter, data)
+        self._render_non_self(parameter, data)
+
+    @functools.cached_property
+    def length_name(self) -> str:
+        """Computes the name of the associated "length" variable."""
+        assert self.length is not None
+        return self.parser_name + "_length"
+
+    # Why is this one broken out separately?
+    # For "positional-only" function parsing,
+    # which generates a bunch of PyArg_ParseTuple calls.
+    def parse_argument(self, args: list[str]) -> None:
+        assert not (self.converter and self.encoding)
+        if self.format_unit == 'O&':
+            assert self.converter
+            args.append(self.converter)
+
+        if self.encoding:
+            args.append(libclinic.c_repr(self.encoding))
+        elif self.subclass_of:
+            args.append(self.subclass_of)
+
+        s = ("&" if self.parse_by_reference else "") + self.parser_name
+        args.append(s)
+
+        if self.length:
+            args.append(f"&{self.length_name}")
+
+    #
+    # All the functions after here are intended as extension points.
+    #
+
+    def simple_declaration(
+            self,
+            by_reference: bool = False,
+            *,
+            in_parser: bool = False
+    ) -> str:
+        """
+        Computes the basic declaration of the variable.
+        Used in computing the prototype declaration and the
+        variable declaration.
+        """
+        assert isinstance(self.type, str)
+        prototype = [self.type]
+        if by_reference or not self.type.endswith('*'):
+            prototype.append(" ")
+        if by_reference:
+            prototype.append('*')
+        if in_parser:
+            name = self.parser_name
+        else:
+            name = self.name
+            if self.unused:
+                name = f"Py_UNUSED({name})"
+        prototype.append(name)
+        return "".join(prototype)
+
+    def declaration(self, *, in_parser: bool = False) -> str:
+        """
+        The C statement to declare this variable.
+        """
+        declaration = [self.simple_declaration(in_parser=True)]
+        default = self.c_default
+        if not default and self.parameter.group:
+            default = self.c_ignored_default
+        if default:
+            declaration.append(" = ")
+            declaration.append(default)
+        declaration.append(";")
+        if self.length:
+            declaration.append('\n')
+            declaration.append(f"Py_ssize_t {self.length_name};")
+        return "".join(declaration)
+
+    def initialize(self) -> str:
+        """
+        The C statements required to set up this variable before parsing.
+        Returns a string containing this code indented at column 0.
+        If no initialization is necessary, returns an empty string.
+        """
+        return ""
+
+    def modify(self) -> str:
+        """
+        The C statements required to modify this variable after parsing.
+        Returns a string containing this code indented at column 0.
+        If no modification is necessary, returns an empty string.
+        """
+        return ""
+
+    def post_parsing(self) -> str:
+        """
+        The C statements required to do some operations after the end of parsing but before cleaning up.
+        Return a string containing this code indented at column 0.
+        If no operation is necessary, return an empty string.
+        """
+        return ""
+
+    def cleanup(self) -> str:
+        """
+        The C statements required to clean up after this variable.
+        Returns a string containing this code indented at column 0.
+        If no cleanup is necessary, returns an empty string.
+        """
+        return ""
+
+    def pre_render(self) -> None:
+        """
+        A second initialization function, like converter_init,
+        called just before rendering.
+        You are permitted to examine self.function here.
+        """
+        pass
+
+    def bad_argument(self, displayname: str, expected: str, *, limited_capi: bool, expected_literal: bool = True) -> str:
+        assert '"' not in expected
+        if limited_capi:
+            if expected_literal:
+                return (f'PyErr_Format(PyExc_TypeError, '
+                        f'"{{{{name}}}}() {displayname} must be {expected}, not %.50s", '
+                        f'{{argname}} == Py_None ? "None" : Py_TYPE({{argname}})->tp_name);')
+            else:
+                return (f'PyErr_Format(PyExc_TypeError, '
+                        f'"{{{{name}}}}() {displayname} must be %.50s, not %.50s", '
+                        f'"{expected}", '
+                        f'{{argname}} == Py_None ? "None" : Py_TYPE({{argname}})->tp_name);')
+        else:
+            if expected_literal:
+                expected = f'"{expected}"'
+            self.add_include('pycore_modsupport.h', '_PyArg_BadArgument()')
+            return f'_PyArg_BadArgument("{{{{name}}}}", "{displayname}", {expected}, {{argname}});'
+
+    def format_code(self, fmt: str, *,
+                    argname: str,
+                    bad_argument: str | None = None,
+                    bad_argument2: str | None = None,
+                    **kwargs: Any) -> str:
+        if '{bad_argument}' in fmt:
+            if not bad_argument:
+                raise TypeError("required 'bad_argument' argument")
+            fmt = fmt.replace('{bad_argument}', bad_argument)
+        if '{bad_argument2}' in fmt:
+            if not bad_argument2:
+                raise TypeError("required 'bad_argument2' argument")
+            fmt = fmt.replace('{bad_argument2}', bad_argument2)
+        return fmt.format(argname=argname, paramname=self.parser_name, **kwargs)
+
+    def use_converter(self) -> None:
+        """Method called when self.converter is used to parse an argument."""
+        pass
+
+    def parse_arg(self, argname: str, displayname: str, *, limited_capi: bool) -> str | None:
+        if self.format_unit == 'O&':
+            self.use_converter()
+            return self.format_code("""
+                if (!{converter}({argname}, &{paramname})) {{{{
+                    goto exit;
+                }}}}
+                """,
+                argname=argname,
+                converter=self.converter)
+        if self.format_unit == 'O!':
+            cast = '(%s)' % self.type if self.type != 'PyObject *' else ''
+            if self.subclass_of in type_checks:
+                typecheck, typename = type_checks[self.subclass_of]
+                return self.format_code("""
+                    if (!{typecheck}({argname})) {{{{
+                        {bad_argument}
+                        goto exit;
+                    }}}}
+                    {paramname} = {cast}{argname};
+                    """,
+                    argname=argname,
+                    bad_argument=self.bad_argument(displayname, typename, limited_capi=limited_capi),
+                    typecheck=typecheck, typename=typename, cast=cast)
+            return self.format_code("""
+                if (!PyObject_TypeCheck({argname}, {subclass_of})) {{{{
+                    {bad_argument}
+                    goto exit;
+                }}}}
+                {paramname} = {cast}{argname};
+                """,
+                argname=argname,
+                bad_argument=self.bad_argument(displayname, '({subclass_of})->tp_name',
+                                               expected_literal=False, limited_capi=limited_capi),
+                subclass_of=self.subclass_of, cast=cast)
+        if self.format_unit == 'O':
+            cast = '(%s)' % self.type if self.type != 'PyObject *' else ''
+            return self.format_code("""
+                {paramname} = {cast}{argname};
+                """,
+                argname=argname, cast=cast)
+        return None
+
+    def set_template_dict(self, template_dict: TemplateDict) -> None:
+        pass
+
+    @property
+    def parser_name(self) -> str:
+        if self.name in libclinic.CLINIC_PREFIXED_ARGS: # bpo-39741
+            return libclinic.CLINIC_PREFIX + self.name
+        else:
+            return self.name
+
+    def add_include(self, name: str, reason: str,
+                    *, condition: str | None = None) -> None:
+        include = Include(name, reason, condition)
+        self.includes.append(include)
+
+
+ConverterType = Callable[..., CConverter]
+ConverterDict = dict[str, ConverterType]
+
+# maps strings to callables.
+# these callables must be of the form:
+#   def foo(name, default, *, ...)
+# The callable may have any number of keyword-only parameters.
+# The callable must return a CConverter object.
+# The callable should not call builtins.print.
+converters: ConverterDict = {}
+
+# maps strings to callables.
+# these callables follow the same rules as those for "converters" above.
+# note however that they will never be called with keyword-only parameters.
+legacy_converters: ConverterDict = {}
diff --git a/Tools/clinic/libclinic/crenderdata.py b/Tools/clinic/libclinic/crenderdata.py
new file mode 100644
index 0000000..58976b8
--- /dev/null
+++ b/Tools/clinic/libclinic/crenderdata.py
@@ -0,0 +1,81 @@
+import dataclasses as dc
+
+
+TemplateDict = dict[str, str]
+
+
+class CRenderData:
+    def __init__(self) -> None:
+
+        # The C statements to declare variables.
+        # Should be full lines with \n eol characters.
+        self.declarations: list[str] = []
+
+        # The C statements required to initialize the variables before the parse call.
+        # Should be full lines with \n eol characters.
+        self.initializers: list[str] = []
+
+        # The C statements needed to dynamically modify the values
+        # parsed by the parse call, before calling the impl.
+        self.modifications: list[str] = []
+
+        # The entries for the "keywords" array for PyArg_ParseTuple.
+        # Should be individual strings representing the names.
+        self.keywords: list[str] = []
+
+        # The "format units" for PyArg_ParseTuple.
+        # Should be individual strings that will get
+        self.format_units: list[str] = []
+
+        # The varargs arguments for PyArg_ParseTuple.
+        self.parse_arguments: list[str] = []
+
+        # The parameter declarations for the impl function.
+        self.impl_parameters: list[str] = []
+
+        # The arguments to the impl function at the time it's called.
+        self.impl_arguments: list[str] = []
+
+        # For return converters: the name of the variable that
+        # should receive the value returned by the impl.
+        self.return_value = "return_value"
+
+        # For return converters: the code to convert the return
+        # value from the parse function.  This is also where
+        # you should check the _return_value for errors, and
+        # "goto exit" if there are any.
+        self.return_conversion: list[str] = []
+        self.converter_retval = "_return_value"
+
+        # The C statements required to do some operations
+        # after the end of parsing but before cleaning up.
+        # These operations may be, for example, memory deallocations which
+        # can only be done without any error happening during argument parsing.
+        self.post_parsing: list[str] = []
+
+        # The C statements required to clean up after the impl call.
+        self.cleanup: list[str] = []
+
+        # The C statements to generate critical sections (per-object locking).
+        self.lock: list[str] = []
+        self.unlock: list[str] = []
+
+
+@dc.dataclass(slots=True, frozen=True)
+class Include:
+    """
+    An include like: #include "pycore_long.h"   // _Py_ID()
+    """
+    # Example: "pycore_long.h".
+    filename: str
+
+    # Example: "_Py_ID()".
+    reason: str
+
+    # None means unconditional include.
+    # Example: "#if defined(Py_BUILD_CORE) && !defined(Py_BUILD_CORE_MODULE)".
+    condition: str | None
+
+    def sort_key(self) -> tuple[str, str]:
+        # order: '#if' comes before 'NO_CONDITION'
+        return (self.condition or 'NO_CONDITION', self.filename)
diff --git a/Tools/clinic/libclinic/function.py b/Tools/clinic/libclinic/function.py
index 48cb7d0..4fafedb 100644
--- a/Tools/clinic/libclinic/function.py
+++ b/Tools/clinic/libclinic/function.py
@@ -6,7 +6,8 @@ import functools
 import inspect
 from typing import Final, Any, TYPE_CHECKING
 if TYPE_CHECKING:
-    from clinic import Clinic, CConverter, CReturnConverter, self_converter
+    from clinic import Clinic, CReturnConverter, self_converter
+    from libclinic.converter import CConverter
 
 from libclinic import VersionTuple, unspecified