gh-132661: Implement PEP 750 (#132662)

Co-authored-by: Lysandros Nikolaou <lisandrosnik@gmail.com>
Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>
Co-authored-by: Adam Turner <9087854+AA-Turner@users.noreply.github.com>
Co-authored-by: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com>
Co-authored-by: Wingy <git@wingysam.xyz>
Co-authored-by: Koudai Aono <koxudaxi@gmail.com>
Co-authored-by: Dave Peck <davepeck@gmail.com>
Co-authored-by: Terry Jan Reedy <tjreedy@udel.edu>
Co-authored-by: Paul Everitt <pauleveritt@me.com>
Co-authored-by: sobolevn <mail@sobolevn.me>

Objects/interpolationobject.c

@@ -0,0 +1,229 @@
+/* t-string Interpolation object implementation */
+
+#include "Python.h"
+#include "pycore_initconfig.h"    // _PyStatus_OK
+#include "pycore_interpolation.h"
+#include "pycore_typeobject.h"    // _PyType_GetDict
+
+static int
+_conversion_converter(PyObject *arg, PyObject **conversion)
+{
+    if (arg == Py_None) {
+        return 1;
+    }
+
+    if (!PyUnicode_Check(arg)) {
+        PyErr_Format(PyExc_TypeError,
+            "Interpolation() argument 'conversion' must be str, not %T",
+            arg);
+        return 0;
+    }
+
+    Py_ssize_t len;
+    const char *conv_str = PyUnicode_AsUTF8AndSize(arg, &len);
+    if (len != 1 || !(conv_str[0] == 'a' || conv_str[0] == 'r' || conv_str[0] == 's')) {
+        PyErr_SetString(PyExc_ValueError,
+            "Interpolation() argument 'conversion' must be one of 's', 'a' or 'r'");
+        return 0;
+    }
+
+    *conversion = arg;
+    return 1;
+}
+
+#include "clinic/interpolationobject.c.h"
+
+/*[clinic input]
+class Interpolation "interpolationobject *" "&_PyInterpolation_Type"
+[clinic start generated code]*/
+/*[clinic end generated code: output=da39a3ee5e6b4b0d input=161c64a16f9c4544]*/
+
+typedef struct {
+    PyObject_HEAD
+    PyObject *value;
+    PyObject *expression;
+    PyObject *conversion;
+    PyObject *format_spec;
+} interpolationobject;
+
+#define interpolationobject_CAST(op) \
+    (assert(_PyInterpolation_CheckExact(op)), _Py_CAST(interpolationobject*, (op)))
+
+/*[clinic input]
+@classmethod
+Interpolation.__new__ as interpolation_new
+
+    value: object
+    expression: object(subclass_of='&PyUnicode_Type')
+    conversion: object(converter='_conversion_converter') = None
+    format_spec: object(subclass_of='&PyUnicode_Type', c_default='&_Py_STR(empty)') = ""
+[clinic start generated code]*/
+
+static PyObject *
+interpolation_new_impl(PyTypeObject *type, PyObject *value,
+                       PyObject *expression, PyObject *conversion,
+                       PyObject *format_spec)
+/*[clinic end generated code: output=6488e288765bc1a9 input=d91711024068528c]*/
+{
+    interpolationobject *self = PyObject_GC_New(interpolationobject, type);
+    if (!self) {
+        return NULL;
+    }
+
+    self->value = Py_NewRef(value);
+    self->expression = Py_NewRef(expression);
+    self->conversion = Py_NewRef(conversion);
+    self->format_spec = Py_NewRef(format_spec);
+    PyObject_GC_Track(self);
+    return (PyObject *) self;
+}
+
+static void
+interpolation_dealloc(PyObject *op)
+{
+    PyObject_GC_UnTrack(op);
+    Py_TYPE(op)->tp_clear(op);
+    Py_TYPE(op)->tp_free(op);
+}
+
+static int
+interpolation_clear(PyObject *op)
+{
+    interpolationobject *self = interpolationobject_CAST(op);
+    Py_CLEAR(self->value);
+    Py_CLEAR(self->expression);
+    Py_CLEAR(self->conversion);
+    Py_CLEAR(self->format_spec);
+    return 0;
+}
+
+static int
+interpolation_traverse(PyObject *op, visitproc visit, void *arg)
+{
+    interpolationobject *self = interpolationobject_CAST(op);
+    Py_VISIT(self->value);
+    Py_VISIT(self->expression);
+    Py_VISIT(self->conversion);
+    Py_VISIT(self->format_spec);
+    return 0;
+}
+
+static PyObject *
+interpolation_repr(PyObject *op)
+{
+    interpolationobject *self = interpolationobject_CAST(op);
+    return PyUnicode_FromFormat("%s(%R, %R, %R, %R)",
+                                _PyType_Name(Py_TYPE(self)), self->value, self->expression,
+                                self->conversion, self->format_spec);
+}
+
+static PyMemberDef interpolation_members[] = {
+    {"value", Py_T_OBJECT_EX, offsetof(interpolationobject, value), Py_READONLY, "Value"},
+    {"expression", Py_T_OBJECT_EX, offsetof(interpolationobject, expression), Py_READONLY, "Expression"},
+    {"conversion", Py_T_OBJECT_EX, offsetof(interpolationobject, conversion), Py_READONLY, "Conversion"},
+    {"format_spec", Py_T_OBJECT_EX, offsetof(interpolationobject, format_spec), Py_READONLY, "Format specifier"},
+    {NULL}
+};
+
+static PyObject*
+interpolation_reduce(PyObject *op, PyObject *Py_UNUSED(dummy))
+{
+    interpolationobject *self = interpolationobject_CAST(op);
+    return Py_BuildValue("(O(OOOO))", (PyObject *)Py_TYPE(op),
+                         self->value, self->expression,
+                         self->conversion, self->format_spec);
+}
+
+static PyMethodDef interpolation_methods[] = {
+    {"__reduce__", interpolation_reduce, METH_NOARGS,
+        PyDoc_STR("__reduce__() -> (cls, state)")},
+    {NULL, NULL},
+};
+
+PyTypeObject _PyInterpolation_Type = {
+    PyVarObject_HEAD_INIT(NULL, 0)
+    .tp_name = "string.templatelib.Interpolation",
+    .tp_doc = PyDoc_STR("Interpolation object"),
+    .tp_basicsize = sizeof(interpolationobject),
+    .tp_itemsize = 0,
+    .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC,
+    .tp_new = interpolation_new,
+    .tp_alloc = PyType_GenericAlloc,
+    .tp_dealloc = interpolation_dealloc,
+    .tp_clear = interpolation_clear,
+    .tp_free = PyObject_GC_Del,
+    .tp_repr = interpolation_repr,
+    .tp_members = interpolation_members,
+    .tp_methods = interpolation_methods,
+    .tp_traverse = interpolation_traverse,
+};
+
+PyStatus
+_PyInterpolation_InitTypes(PyInterpreterState *interp)
+{
+    PyObject *tuple = Py_BuildValue("(ssss)", "value", "expression", "conversion", "format_spec");
+    if (!tuple) {
+        goto error;
+    }
+
+    PyObject *dict = _PyType_GetDict(&_PyInterpolation_Type);
+    if (!dict) {
+        Py_DECREF(tuple);
+        goto error;
+    }
+
+    int status = PyDict_SetItemString(dict, "__match_args__", tuple);
+    Py_DECREF(tuple);
+    if (status < 0) {
+        goto error;
+    }
+    return _PyStatus_OK();
+
+error:
+    return _PyStatus_ERR("Can't initialize interpolation types");
+}
+
+PyObject *
+_PyInterpolation_Build(PyObject *value, PyObject *str, int conversion, PyObject *format_spec)
+{
+    interpolationobject *interpolation = PyObject_GC_New(interpolationobject, &_PyInterpolation_Type);
+    if (!interpolation) {
+        return NULL;
+    }
+
+    interpolation->value = Py_NewRef(value);
+    interpolation->expression = Py_NewRef(str);
+    interpolation->format_spec = Py_NewRef(format_spec);
+    interpolation->conversion = NULL;
+
+    if (conversion == 0) {
+        interpolation->conversion = Py_None;
+    }
+    else {
+        switch (conversion) {
+            case FVC_ASCII:
+                interpolation->conversion = _Py_LATIN1_CHR('a');
+                break;
+            case FVC_REPR:
+                interpolation->conversion = _Py_LATIN1_CHR('r');
+                break;
+            case FVC_STR:
+                interpolation->conversion = _Py_LATIN1_CHR('s');
+                break;
+            default:
+                PyErr_SetString(PyExc_SystemError,
+                    "Interpolation() argument 'conversion' must be one of 's', 'a' or 'r'");
+                Py_DECREF(interpolation);
+                return NULL;
+        }
+    }
+
+    PyObject_GC_Track(interpolation);
+    return (PyObject *) interpolation;
+}
+
+PyObject *
+_PyInterpolation_GetValueRef(PyObject *interpolation)
+{
+    return Py_NewRef(interpolationobject_CAST(interpolation)->value);
+}