From da52601d1f8e524359cf09698811acb1f889203e Mon Sep 17 00:00:00 2001
From: Victor Stinner <vstinner@python.org>
Date: Mon, 9 Jun 2025 14:45:13 +0200
Subject: [PATCH] Add PyUnicodeWriter_WriteASCII()

---
 docs/api.rst                        |  4 ++++
 docs/changelog.rst                  |  1 +
 pythoncapi_compat.h                 | 12 ++++++++++++
 tests/test_pythoncapi_compat_cext.c |  7 ++++++-
 4 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/docs/api.rst b/docs/api.rst
index 609edbd..6efae15 100644
--- a/docs/api.rst
+++ b/docs/api.rst
@@ -136,6 +136,10 @@ Python 3.14
 
    See `PyUnicodeWriter_WriteUTF8() documentation <https://docs.python.org/dev/c-api/unicode.html#c.PyUnicodeWriter_WriteUTF8>`__.
 
+.. c:function:: int PyUnicodeWriter_WriteASCII(PyUnicodeWriter *writer, const char *str, Py_ssize_t size)
+
+   See `PyUnicodeWriter_WriteASCII() documentation <https://docs.python.org/dev/c-api/unicode.html#c.PyUnicodeWriter_WriteASCII>`__.
+
 .. c:function:: int PyUnicodeWriter_WriteWideChar(PyUnicodeWriter *writer, const wchar_t *str, Py_ssize_t size)
 
    See `PyUnicodeWriter_WriteWideChar() documentation <https://docs.python.org/dev/c-api/unicode.html#c.PyUnicodeWriter_WriteWideChar>`__.
diff --git a/docs/changelog.rst b/docs/changelog.rst
index bb981c4..b8e3a86 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -1,6 +1,7 @@
 Changelog
 =========
 
+* 2025-06-09: Add ``PyUnicodeWriter_WriteASCII()`` function.
 * 2025-06-03: Add functions:
 
   * ``PySys_GetAttr()``
diff --git a/pythoncapi_compat.h b/pythoncapi_compat.h
index eb84307..20646af 100644
--- a/pythoncapi_compat.h
+++ b/pythoncapi_compat.h
@@ -1456,6 +1456,18 @@ PyUnicodeWriter_WriteUTF8(PyUnicodeWriter *writer,
     return res;
 }
 
+static inline int
+PyUnicodeWriter_WriteASCII(PyUnicodeWriter *writer,
+                           const char *str, Py_ssize_t size)
+{
+    if (size < 0) {
+        size = (Py_ssize_t)strlen(str);
+    }
+
+    return _PyUnicodeWriter_WriteASCIIString((_PyUnicodeWriter*)writer,
+                                             str, size);
+}
+
 static inline int
 PyUnicodeWriter_WriteWideChar(PyUnicodeWriter *writer,
                               const wchar_t *str, Py_ssize_t size)
diff --git a/tests/test_pythoncapi_compat_cext.c b/tests/test_pythoncapi_compat_cext.c
index 82cf387..6e76316 100644
--- a/tests/test_pythoncapi_compat_cext.c
+++ b/tests/test_pythoncapi_compat_cext.c
@@ -1847,6 +1847,11 @@ test_unicodewriter(PyObject *Py_UNUSED(self), PyObject *Py_UNUSED(args))
         goto error;
     }
 
+    // test PyUnicodeWriter_WriteASCII()
+    if (PyUnicodeWriter_WriteASCII(writer, " non-ASCII", -1) < 0) {
+        goto error;
+    }
+
     // test PyUnicodeWriter_WriteUTF8()
     if (PyUnicodeWriter_WriteUTF8(writer, " valu\xC3\xA9", -1) < 0) {
         goto error;
@@ -1870,7 +1875,7 @@ test_unicodewriter(PyObject *Py_UNUSED(self), PyObject *Py_UNUSED(args))
         if (result == NULL) {
             return NULL;
         }
-        assert(PyUnicode_EqualToUTF8(result, "var=long valu\xC3\xA9 'repr'"));
+        assert(PyUnicode_EqualToUTF8(result, "var=long non-ASCII valu\xC3\xA9 'repr'"));
         Py_DECREF(result);
     }