gh-161172: Add PyUnicodeWriter to the limited C API

Keep tests in _testcapi to access the deprecated function
_PyUnicodeWriter_WriteLatin1String() which is excluded from the
limited C API.

Author: vstinner

Doc/data/stable_abi.dat

@@ -1384,6 +1384,9 @@ New features
   API.
   (Contributed by Nathan Goldbaum and Victor Stinner in :gh:`158842`.)
 
+* Add the :ref:`PyUnicodeWriter API <PyUnicodeWriter>` to the limited C API.
+  (Contributed by Victor Stinner in :gh:`161172`.)
+
 Porting to Python 3.16
 ----------------------
 

Doc/whatsnew/3.16.rst

@@ -471,57 +471,6 @@ PyAPI_FUNC(PyObject*) PyUnicode_FromKindAndData(
     Py_ssize_t size);
 
 
-/* --- Public PyUnicodeWriter API ----------------------------------------- */
-
-typedef struct PyUnicodeWriter PyUnicodeWriter;
-
-PyAPI_FUNC(PyUnicodeWriter*) PyUnicodeWriter_Create(Py_ssize_t length);
-PyAPI_FUNC(void) PyUnicodeWriter_Discard(PyUnicodeWriter *writer);
-PyAPI_FUNC(PyObject*) PyUnicodeWriter_Finish(PyUnicodeWriter *writer);
-
-PyAPI_FUNC(int) PyUnicodeWriter_WriteChar(
-    PyUnicodeWriter *writer,
-    Py_UCS4 ch);
-PyAPI_FUNC(int) PyUnicodeWriter_WriteUTF8(
-    PyUnicodeWriter *writer,
-    const char *str,
-    Py_ssize_t size);
-PyAPI_FUNC(int) PyUnicodeWriter_WriteASCII(
-    PyUnicodeWriter *writer,
-    const char *str,
-    Py_ssize_t size);
-PyAPI_FUNC(int) PyUnicodeWriter_WriteWideChar(
-    PyUnicodeWriter *writer,
-    const wchar_t *str,
-    Py_ssize_t size);
-PyAPI_FUNC(int) PyUnicodeWriter_WriteUCS4(
-    PyUnicodeWriter *writer,
-    const Py_UCS4 *str,
-    Py_ssize_t size);
-
-PyAPI_FUNC(int) PyUnicodeWriter_WriteStr(
-    PyUnicodeWriter *writer,
-    PyObject *obj);
-PyAPI_FUNC(int) PyUnicodeWriter_WriteRepr(
-    PyUnicodeWriter *writer,
-    PyObject *obj);
-PyAPI_FUNC(int) PyUnicodeWriter_WriteSubstring(
-    PyUnicodeWriter *writer,
-    PyObject *str,
-    Py_ssize_t start,
-    Py_ssize_t end);
-PyAPI_FUNC(int) PyUnicodeWriter_Format(
-    PyUnicodeWriter *writer,
-    const char *format,
-    ...);
-PyAPI_FUNC(int) PyUnicodeWriter_DecodeUTF8Stateful(
-    PyUnicodeWriter *writer,
-    const char *str,            /* UTF-8 encoded string */
-    Py_ssize_t size,            /* size of string */
-    const char *errors,         /* error handling */
-    Py_ssize_t *consumed);      /* bytes consumed */
-
-
 /* --- Private _PyUnicodeWriter API --------------------------------------- */
 
 typedef struct {

Include/cpython/unicodeobject.h

@@ -954,7 +954,59 @@ PyAPI_FUNC(int) PyUnicode_Contains(
 
 PyAPI_FUNC(int) PyUnicode_IsIdentifier(PyObject *s);
 
-/* === Characters Type APIs =============================================== */
+
+/* === Public PyUnicodeWriter API ========================================= */
+
+#if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 >= _Py_PACK_VERSION(3, 16)
+typedef struct PyUnicodeWriter PyUnicodeWriter;
+
+PyAPI_FUNC(PyUnicodeWriter*) PyUnicodeWriter_Create(Py_ssize_t length);
+PyAPI_FUNC(void) PyUnicodeWriter_Discard(PyUnicodeWriter *writer);
+PyAPI_FUNC(PyObject*) PyUnicodeWriter_Finish(PyUnicodeWriter *writer);
+
+PyAPI_FUNC(int) PyUnicodeWriter_WriteChar(
+    PyUnicodeWriter *writer,
+    Py_UCS4 ch);
+PyAPI_FUNC(int) PyUnicodeWriter_WriteUTF8(
+    PyUnicodeWriter *writer,
+    const char *str,
+    Py_ssize_t size);
+PyAPI_FUNC(int) PyUnicodeWriter_WriteASCII(
+    PyUnicodeWriter *writer,
+    const char *str,
+    Py_ssize_t size);
+PyAPI_FUNC(int) PyUnicodeWriter_WriteWideChar(
+    PyUnicodeWriter *writer,
+    const wchar_t *str,
+    Py_ssize_t size);
+PyAPI_FUNC(int) PyUnicodeWriter_WriteUCS4(
+    PyUnicodeWriter *writer,
+    const Py_UCS4 *str,
+    Py_ssize_t size);
+
+PyAPI_FUNC(int) PyUnicodeWriter_WriteStr(
+    PyUnicodeWriter *writer,
+    PyObject *obj);
+PyAPI_FUNC(int) PyUnicodeWriter_WriteRepr(
+    PyUnicodeWriter *writer,
+    PyObject *obj);
+PyAPI_FUNC(int) PyUnicodeWriter_WriteSubstring(
+    PyUnicodeWriter *writer,
+    PyObject *str,
+    Py_ssize_t start,
+    Py_ssize_t end);
+PyAPI_FUNC(int) PyUnicodeWriter_Format(
+    PyUnicodeWriter *writer,
+    const char *format,
+    ...);
+PyAPI_FUNC(int) PyUnicodeWriter_DecodeUTF8Stateful(
+    PyUnicodeWriter *writer,
+    const char *str,            /* UTF-8 encoded string */
+    Py_ssize_t size,            /* size of string */
+    const char *errors,         /* error handling */
+    Py_ssize_t *consumed);      /* bytes consumed */
+#endif  // !defined(Py_LIMITED_API) || Py_LIMITED_API+0 >= _Py_PACK_VERSION(3, 16)
+
 
 #ifndef Py_LIMITED_API
 #  define Py_CPYTHON_UNICODEOBJECT_H

Include/unicodeobject.h

@@ -0,0 +1,2 @@
+Add the :ref:`PyUnicodeWriter API <PyUnicodeWriter>` to the limited C API.
+Patch by Victor Stinner.

Lib/test/test_stable_abi_ctypes.py

@@ -2915,3 +2915,29 @@
     added = '3.16'
 [macro.Py_XSETREF]
     added = '3.16'
+[function.PyUnicodeWriter_Create]
+    added = '3.16'
+[function.PyUnicodeWriter_Discard]
+    added = '3.16'
+[function.PyUnicodeWriter_Finish]
+    added = '3.16'
+[function.PyUnicodeWriter_WriteChar]
+    added = '3.16'
+[function.PyUnicodeWriter_WriteUTF8]
+    added = '3.16'
+[function.PyUnicodeWriter_WriteASCII]
+    added = '3.16'
+[function.PyUnicodeWriter_WriteWideChar]
+    added = '3.16'
+[function.PyUnicodeWriter_WriteUCS4]
+    added = '3.16'
+[function.PyUnicodeWriter_WriteStr]
+    added = '3.16'
+[function.PyUnicodeWriter_WriteRepr]
+    added = '3.16'
+[function.PyUnicodeWriter_WriteSubstring]
+    added = '3.16'
+[function.PyUnicodeWriter_Format]
+    added = '3.16'
+[function.PyUnicodeWriter_DecodeUTF8Stateful]
+    added = '3.16'