Issue #7330: Implement width and precision (ex: "%5.3s") for the format string

of PyUnicode_FromFormat() function, original patch written by Ysj Ray.

Doc/c-api/unicode.rst

@@ -526,12 +526,23 @@ APIs:
       The `"%lld"` and `"%llu"` format specifiers are only available
       when :const:`HAVE_LONG_LONG` is defined.
 
+   .. note::
+      The width formatter unit is number of characters rather than bytes.
+      The precision formatter unit is number of bytes for ``"%s"`` and
+      ``"%V"`` (if the ``PyObject*`` argument is NULL), and a number of
+      characters for ``"%A"``, ``"%U"``, ``"%S"``, ``"%R"`` and ``"%V"``
+      (if the ``PyObject*`` argument is not NULL).
+
    .. versionchanged:: 3.2
       Support for ``"%lld"`` and ``"%llu"`` added.
 
    .. versionchanged:: 3.3
       Support for ``"%li"``, ``"%lli"`` and ``"%zi"`` added.
 
+   .. versionchanged:: 3.4
+      Support width and precision formatter for ``"%s"``, ``"%A"``, ``"%U"``,
+      ``"%V"``, ``"%S"``, ``"%R"`` added.
+
 
 .. c:function:: PyObject* PyUnicode_FromFormatV(const char *format, va_list vargs)
 

Lib/test/test_unicode.py

@@ -2007,9 +2007,13 @@ class UnicodeTest(string_tests.CommonTest,
                 for arg in args)
             return _PyUnicode_FromFormat(format, *cargs)
 
+        def check_format(expected, format, *args):
+            text = PyUnicode_FromFormat(format, *args)
+            self.assertEqual(expected, text)
+
         # ascii format, non-ascii argument
-        text = PyUnicode_FromFormat(b'ascii\x7f=%U', 'unicode\xe9')
+        check_format('ascii\x7f=unicode\xe9',
-        self.assertEqual(text, 'ascii\x7f=unicode\xe9')
+                     b'ascii\x7f=%U', 'unicode\xe9')
 
         # non-ascii format, ascii argument: ensure that PyUnicode_FromFormatV()
         # raises an error
@@ -2019,83 +2023,200 @@ class UnicodeTest(string_tests.CommonTest,
             PyUnicode_FromFormat, b'unicode\xe9=%s', 'ascii')
 
         # test "%c"
-        self.assertEqual(PyUnicode_FromFormat(b'%c', c_int(0xabcd)), '\uabcd')
+        check_format('\uabcd',
-        self.assertEqual(PyUnicode_FromFormat(b'%c', c_int(0x10ffff)), '\U0010ffff')
+                     b'%c', c_int(0xabcd))
+        check_format('\U0010ffff',
+                     b'%c', c_int(0x10ffff))
 
         # test "%"
-        self.assertEqual(PyUnicode_FromFormat(b'%'), '%')
+        check_format('%',
-        self.assertEqual(PyUnicode_FromFormat(b'%%'), '%')
+                     b'%')
-        self.assertEqual(PyUnicode_FromFormat(b'%%s'), '%s')
+        check_format('%',
-        self.assertEqual(PyUnicode_FromFormat(b'[%%]'), '[%]')
+                     b'%%')
-        self.assertEqual(PyUnicode_FromFormat(b'%%%s', b'abc'), '%abc')
+        check_format('%s',
+                     b'%%s')
+        check_format('[%]',
+                     b'[%%]')
+        check_format('%abc',
+                     b'%%%s', b'abc')
+
+        # truncated string
+        check_format('abc',
+                     b'%.3s', b'abcdef')
+        check_format('abc[\ufffd',
+                     b'%.5s', 'abc[\u20ac]'.encode('utf8'))
+        check_format("'\\u20acABC'",
+                     b'%A', '\u20acABC')
+        check_format("'\\u20",
+                     b'%.5A', '\u20acABCDEF')
+        check_format("'\u20acABC'",
+                     b'%R', '\u20acABC')
+        check_format("'\u20acA",
+                     b'%.3R', '\u20acABCDEF')
+        check_format('\u20acAB',
+                     b'%.3S', '\u20acABCDEF')
+        check_format('\u20acAB',
+                     b'%.3U', '\u20acABCDEF')
+        check_format('\u20acAB',
+                     b'%.3V', '\u20acABCDEF', None)
+        check_format('abc[\ufffd',
+                     b'%.5V', None, 'abc[\u20ac]'.encode('utf8'))
+
+        # following tests comes from #7330
+        # test width modifier and precision modifier with %S
+        check_format("repr=  abc",
+                     b'repr=%5S', 'abc')
+        check_format("repr=ab",
+                     b'repr=%.2S', 'abc')
+        check_format("repr=   ab",
+                     b'repr=%5.2S', 'abc')
+
+        # test width modifier and precision modifier with %R
+        check_format("repr=   'abc'",
+                     b'repr=%8R', 'abc')
+        check_format("repr='ab",
+                     b'repr=%.3R', 'abc')
+        check_format("repr=  'ab",
+                     b'repr=%5.3R', 'abc')
+
+        # test width modifier and precision modifier with %A
+        check_format("repr=   'abc'",
+                     b'repr=%8A', 'abc')
+        check_format("repr='ab",
+                     b'repr=%.3A', 'abc')
+        check_format("repr=  'ab",
+                     b'repr=%5.3A', 'abc')
+
+        # test width modifier and precision modifier with %s
+        check_format("repr=  abc",
+                     b'repr=%5s', b'abc')
+        check_format("repr=ab",
+                     b'repr=%.2s', b'abc')
+        check_format("repr=   ab",
+                     b'repr=%5.2s', b'abc')
+
+        # test width modifier and precision modifier with %U
+        check_format("repr=  abc",
+                     b'repr=%5U', 'abc')
+        check_format("repr=ab",
+                     b'repr=%.2U', 'abc')
+        check_format("repr=   ab",
+                     b'repr=%5.2U', 'abc')
+
+        # test width modifier and precision modifier with %V
+        check_format("repr=  abc",
+                     b'repr=%5V', 'abc', b'123')
+        check_format("repr=ab",
+                     b'repr=%.2V', 'abc', b'123')
+        check_format("repr=   ab",
+                     b'repr=%5.2V', 'abc', b'123')
+        check_format("repr=  123",
+                     b'repr=%5V', None, b'123')
+        check_format("repr=12",
+                     b'repr=%.2V', None, b'123')
+        check_format("repr=   12",
+                     b'repr=%5.2V', None, b'123')
 
         # test integer formats (%i, %d, %u)
-        self.assertEqual(PyUnicode_FromFormat(b'%03i', c_int(10)), '010')
+        check_format('010',
-        self.assertEqual(PyUnicode_FromFormat(b'%0.4i', c_int(10)), '0010')
+                     b'%03i', c_int(10))
-        self.assertEqual(PyUnicode_FromFormat(b'%i', c_int(-123)), '-123')
+        check_format('0010',
-        self.assertEqual(PyUnicode_FromFormat(b'%li', c_long(-123)), '-123')
+                     b'%0.4i', c_int(10))
-        self.assertEqual(PyUnicode_FromFormat(b'%lli', c_longlong(-123)), '-123')
+        check_format('-123',
-        self.assertEqual(PyUnicode_FromFormat(b'%zi', c_ssize_t(-123)), '-123')
+                     b'%i', c_int(-123))
+        check_format('-123',
+                     b'%li', c_long(-123))
+        check_format('-123',
+                     b'%lli', c_longlong(-123))
+        check_format('-123',
+                     b'%zi', c_ssize_t(-123))
 
-        self.assertEqual(PyUnicode_FromFormat(b'%d', c_int(-123)), '-123')
+        check_format('-123',
-        self.assertEqual(PyUnicode_FromFormat(b'%ld', c_long(-123)), '-123')
+                     b'%d', c_int(-123))
-        self.assertEqual(PyUnicode_FromFormat(b'%lld', c_longlong(-123)), '-123')
+        check_format('-123',
-        self.assertEqual(PyUnicode_FromFormat(b'%zd', c_ssize_t(-123)), '-123')
+                     b'%ld', c_long(-123))
+        check_format('-123',
+                     b'%lld', c_longlong(-123))
+        check_format('-123',
+                     b'%zd', c_ssize_t(-123))
 
-        self.assertEqual(PyUnicode_FromFormat(b'%u', c_uint(123)), '123')
+        check_format('123',
-        self.assertEqual(PyUnicode_FromFormat(b'%lu', c_ulong(123)), '123')
+                     b'%u', c_uint(123))
-        self.assertEqual(PyUnicode_FromFormat(b'%llu', c_ulonglong(123)), '123')
+        check_format('123',
-        self.assertEqual(PyUnicode_FromFormat(b'%zu', c_size_t(123)), '123')
+                     b'%lu', c_ulong(123))
+        check_format('123',
+                     b'%llu', c_ulonglong(123))
+        check_format('123',
+                     b'%zu', c_size_t(123))
 
         # test long output
         min_longlong = -(2 ** (8 * sizeof(c_longlong) - 1))
         max_longlong = -min_longlong - 1
-        self.assertEqual(PyUnicode_FromFormat(b'%lld', c_longlong(min_longlong)), str(min_longlong))
+        check_format(str(min_longlong),
-        self.assertEqual(PyUnicode_FromFormat(b'%lld', c_longlong(max_longlong)), str(max_longlong))
+                     b'%lld', c_longlong(min_longlong))
+        check_format(str(max_longlong),
+                     b'%lld', c_longlong(max_longlong))
         max_ulonglong = 2 ** (8 * sizeof(c_ulonglong)) - 1
-        self.assertEqual(PyUnicode_FromFormat(b'%llu', c_ulonglong(max_ulonglong)), str(max_ulonglong))
+        check_format(str(max_ulonglong),
+                     b'%llu', c_ulonglong(max_ulonglong))
         PyUnicode_FromFormat(b'%p', c_void_p(-1))
 
         # test padding (width and/or precision)
-        self.assertEqual(PyUnicode_FromFormat(b'%010i', c_int(123)), '123'.rjust(10, '0'))
+        check_format('123'.rjust(10, '0'),
-        self.assertEqual(PyUnicode_FromFormat(b'%100i', c_int(123)), '123'.rjust(100))
+                     b'%010i', c_int(123))
-        self.assertEqual(PyUnicode_FromFormat(b'%.100i', c_int(123)), '123'.rjust(100, '0'))
+        check_format('123'.rjust(100),
-        self.assertEqual(PyUnicode_FromFormat(b'%100.80i', c_int(123)), '123'.rjust(80, '0').rjust(100))
+                     b'%100i', c_int(123))
+        check_format('123'.rjust(100, '0'),
+                     b'%.100i', c_int(123))
+        check_format('123'.rjust(80, '0').rjust(100),
+                     b'%100.80i', c_int(123))
 
-        self.assertEqual(PyUnicode_FromFormat(b'%010u', c_uint(123)), '123'.rjust(10, '0'))
+        check_format('123'.rjust(10, '0'),
-        self.assertEqual(PyUnicode_FromFormat(b'%100u', c_uint(123)), '123'.rjust(100))
+                     b'%010u', c_uint(123))
-        self.assertEqual(PyUnicode_FromFormat(b'%.100u', c_uint(123)), '123'.rjust(100, '0'))
+        check_format('123'.rjust(100),
-        self.assertEqual(PyUnicode_FromFormat(b'%100.80u', c_uint(123)), '123'.rjust(80, '0').rjust(100))
+                     b'%100u', c_uint(123))
+        check_format('123'.rjust(100, '0'),
+                     b'%.100u', c_uint(123))
+        check_format('123'.rjust(80, '0').rjust(100),
+                     b'%100.80u', c_uint(123))
 
-        self.assertEqual(PyUnicode_FromFormat(b'%010x', c_int(0x123)), '123'.rjust(10, '0'))
+        check_format('123'.rjust(10, '0'),
-        self.assertEqual(PyUnicode_FromFormat(b'%100x', c_int(0x123)), '123'.rjust(100))
+                     b'%010x', c_int(0x123))
-        self.assertEqual(PyUnicode_FromFormat(b'%.100x', c_int(0x123)), '123'.rjust(100, '0'))
+        check_format('123'.rjust(100),
-        self.assertEqual(PyUnicode_FromFormat(b'%100.80x', c_int(0x123)), '123'.rjust(80, '0').rjust(100))
+                     b'%100x', c_int(0x123))
+        check_format('123'.rjust(100, '0'),
+                     b'%.100x', c_int(0x123))
+        check_format('123'.rjust(80, '0').rjust(100),
+                     b'%100.80x', c_int(0x123))
 
         # test %A
-        text = PyUnicode_FromFormat(b'%%A:%A', 'abc\xe9\uabcd\U0010ffff')
+        check_format(r"%A:'abc\xe9\uabcd\U0010ffff'",
-        self.assertEqual(text, r"%A:'abc\xe9\uabcd\U0010ffff'")
+                     b'%%A:%A', 'abc\xe9\uabcd\U0010ffff')
 
         # test %V
-        text = PyUnicode_FromFormat(b'repr=%V', 'abc', b'xyz')
+        check_format('repr=abc',
-        self.assertEqual(text, 'repr=abc')
+                     b'repr=%V', 'abc', b'xyz')
 
         # Test string decode from parameter of %s using utf-8.
         # b'\xe4\xba\xba\xe6\xb0\x91' is utf-8 encoded byte sequence of
         # '\u4eba\u6c11'
-        text = PyUnicode_FromFormat(b'repr=%V', None, b'\xe4\xba\xba\xe6\xb0\x91')
+        check_format('repr=\u4eba\u6c11',
-        self.assertEqual(text, 'repr=\u4eba\u6c11')
+                     b'repr=%V', None, b'\xe4\xba\xba\xe6\xb0\x91')
 
         #Test replace error handler.
-        text = PyUnicode_FromFormat(b'repr=%V', None, b'abc\xff')
+        check_format('repr=abc\ufffd',
-        self.assertEqual(text, 'repr=abc\ufffd')
+                     b'repr=%V', None, b'abc\xff')
 
         # not supported: copy the raw format string. these tests are just here
         # to check for crashs and should not be considered as specifications
-        self.assertEqual(PyUnicode_FromFormat(b'%1%s', b'abc'), '%s')
+        check_format('%s',
-        self.assertEqual(PyUnicode_FromFormat(b'%1abc'), '%1abc')
+                     b'%1%s', b'abc')
-        self.assertEqual(PyUnicode_FromFormat(b'%+i', c_int(10)), '%+i')
+        check_format('%1abc',
-        self.assertEqual(PyUnicode_FromFormat(b'%.%s', b'abc'), '%.%s')
+                     b'%1abc')
+        check_format('%+i',
+                     b'%+i', c_int(10))
+        check_format('%.%s',
+                     b'%.%s', b'abc')
 
     # Test PyUnicode_AsWideChar()
     def test_aswidechar(self):

Misc/NEWS

@@ -10,6 +10,9 @@ What's New in Python 3.4.0 Alpha 1?
 Core and Builtins
 -----------------
 
+- Issue #7330: Implement width and precision (ex: "%5.3s") for the format
+  string of PyUnicode_FromFormat() function, original patch written by Ysj Ray.
+
 - Issue #1545463: Global variables caught in reference cycles are now
   garbage-collected at shutdown.
 

Objects/unicodeobject.c

@@ -2346,6 +2346,67 @@ makefmt(char *fmt, int longflag, int longlongflag, int size_tflag,
    plus 1 for the sign.  53/22 is an upper bound for log10(256). */
 #define MAX_LONG_LONG_CHARS (2 + (SIZEOF_LONG_LONG*53-1) / 22)
 
+static int
+unicode_fromformat_write_str(_PyUnicodeWriter *writer, PyObject *str,
+                             Py_ssize_t width, Py_ssize_t precision)
+{
+    Py_ssize_t length, fill, arglen;
+    Py_UCS4 maxchar;
+
+    if (PyUnicode_READY(str) == -1)
+        return -1;
+
+    length = PyUnicode_GET_LENGTH(str);
+    if ((precision == -1 || precision >= length)
+        && width <= length)
+        return _PyUnicodeWriter_WriteStr(writer, str);
+
+    if (precision != -1)
+        length = Py_MIN(precision, length);
+
+    arglen = Py_MAX(length, width);
+    if (PyUnicode_MAX_CHAR_VALUE(str) > writer->maxchar)
+        maxchar = _PyUnicode_FindMaxChar(str, 0, length);
+    else
+        maxchar = writer->maxchar;
+
+    if (_PyUnicodeWriter_Prepare(writer, arglen, maxchar) == -1)
+        return -1;
+
+    if (width > length) {
+        fill = width - length;
+        if (PyUnicode_Fill(writer->buffer, writer->pos, fill, ' ') == -1)
+            return -1;
+        writer->pos += fill;
+    }
+
+    _PyUnicode_FastCopyCharacters(writer->buffer, writer->pos,
+                                  str, 0, length);
+    writer->pos += length;
+    return 0;
+}
+
+static int
+unicode_fromformat_write_cstr(_PyUnicodeWriter *writer, const char *str,
+                              Py_ssize_t width, Py_ssize_t precision)
+{
+    /* UTF-8 */
+    Py_ssize_t length;
+    PyObject *unicode;
+    int res;
+
+    length = strlen(str);
+    if (precision != -1)
+        length = Py_MIN(length, precision);
+    unicode = PyUnicode_DecodeUTF8Stateful(str, length, "replace", NULL);
+    if (unicode == NULL)
+        return -1;
+
+    res = unicode_fromformat_write_str(writer, unicode, width, -1);
+    Py_DECREF(unicode);
+    return res;
+}
+
 static const char*
 unicode_fromformat_arg(_PyUnicodeWriter *writer,
                        const char *f, va_list *vargs)
@@ -2353,12 +2414,12 @@ unicode_fromformat_arg(_PyUnicodeWriter *writer,
     const char *p;
     Py_ssize_t len;
     int zeropad;
-    int width;
+    Py_ssize_t width;
-    int precision;
+    Py_ssize_t precision;
     int longflag;
     int longlongflag;
     int size_tflag;
-    int fill;
+    Py_ssize_t fill;
 
     p = f;
     f++;
@@ -2369,28 +2430,36 @@ unicode_fromformat_arg(_PyUnicodeWriter *writer,
     }
 
     /* parse the width.precision part, e.g. "%2.5s" => width=2, precision=5 */
-    width = 0;
+    width = -1;
-    while (Py_ISDIGIT((unsigned)*f)) {
+    if (Py_ISDIGIT((unsigned)*f)) {
-        if (width > (INT_MAX - ((int)*f - '0')) / 10) {
+        width = *f - '0';
-            PyErr_SetString(PyExc_ValueError,
-                            "width too big");
-            return NULL;
-        }
-        width = (width*10) + (*f - '0');
-        f++;
-    }
-    precision = 0;
-    if (*f == '.') {
         f++;
         while (Py_ISDIGIT((unsigned)*f)) {
-            if (precision > (INT_MAX - ((int)*f - '0')) / 10) {
+            if (width > (PY_SSIZE_T_MAX - ((int)*f - '0')) / 10) {
                 PyErr_SetString(PyExc_ValueError,
-                                "precision too big");
+                                "width too big");
                 return NULL;
             }
-            precision = (precision*10) + (*f - '0');
+            width = (width * 10) + (*f - '0');
             f++;
         }
+    }
+    precision = -1;
+    if (*f == '.') {
+        f++;
+        if (Py_ISDIGIT((unsigned)*f)) {
+            precision = (*f - '0');
+            f++;
+            while (Py_ISDIGIT((unsigned)*f)) {
+                if (precision > (PY_SSIZE_T_MAX - ((int)*f - '0')) / 10) {
+                    PyErr_SetString(PyExc_ValueError,
+                                    "precision too big");
+                    return NULL;
+                }
+                precision = (precision * 10) + (*f - '0');
+                f++;
+            }
+        }
         if (*f == '%') {
             /* "%.3%s" => f points to "3" */
             f--;
@@ -2449,6 +2518,7 @@ unicode_fromformat_arg(_PyUnicodeWriter *writer,
         /* used by sprintf */
         char fmt[10]; /* should be enough for "%0lld\0" */
         char buffer[MAX_LONG_LONG_CHARS];
+        Py_ssize_t arglen;
 
         if (*f == 'u') {
             makefmt(fmt, longflag, longlongflag, size_tflag, *f);
@@ -2494,26 +2564,29 @@ unicode_fromformat_arg(_PyUnicodeWriter *writer,
 
         if (precision < len)
             precision = len;
+
+        arglen = Py_MAX(precision, width);
+        assert(ucs1lib_find_max_char((Py_UCS1*)buffer, (Py_UCS1*)buffer + len) <= 127);
+        if (_PyUnicodeWriter_Prepare(writer, arglen, 127) == -1)
+            return NULL;
+
         if (width > precision) {
             Py_UCS4 fillchar;
             fill = width - precision;
             fillchar = zeropad?'0':' ';
-            if (_PyUnicodeWriter_Prepare(writer, fill, fillchar) == -1)
-                return NULL;
             if (PyUnicode_Fill(writer->buffer, writer->pos, fill, fillchar) == -1)
                 return NULL;
             writer->pos += fill;
         }
         if (precision > len) {
             fill = precision - len;
-            if (_PyUnicodeWriter_Prepare(writer, fill, '0') == -1)
-                return NULL;
             if (PyUnicode_Fill(writer->buffer, writer->pos, fill, '0') == -1)
                 return NULL;
             writer->pos += fill;
         }
-        if (_PyUnicodeWriter_WriteCstr(writer, buffer, len) == -1)
+
-            return NULL;
+        unicode_write_cstr(writer->buffer, writer->pos, buffer, len);
+        writer->pos += len;
         break;
     }
 
@@ -2535,8 +2608,11 @@ unicode_fromformat_arg(_PyUnicodeWriter *writer,
             len += 2;
         }
 
-        if (_PyUnicodeWriter_WriteCstr(writer, number, len) == -1)
+        assert(ucs1lib_find_max_char((Py_UCS1*)number, (Py_UCS1*)number + len) <= 127);
+        if (_PyUnicodeWriter_Prepare(writer, len, 127) == -1)
             return NULL;
+        unicode_write_cstr(writer->buffer, writer->pos, number, len);
+        writer->pos += len;
         break;
     }
 
@@ -2544,14 +2620,8 @@ unicode_fromformat_arg(_PyUnicodeWriter *writer,
     {
         /* UTF-8 */
         const char *s = va_arg(*vargs, const char*);
-        PyObject *str = PyUnicode_DecodeUTF8Stateful(s, strlen(s), "replace", NULL);
+        if (unicode_fromformat_write_cstr(writer, s, width, precision) < 0)
-        if (!str)
             return NULL;
-        if (_PyUnicodeWriter_WriteStr(writer, str) == -1) {
-            Py_DECREF(str);
-            return NULL;
-        }
-        Py_DECREF(str);
         break;
     }
 
@@ -2560,7 +2630,7 @@ unicode_fromformat_arg(_PyUnicodeWriter *writer,
         PyObject *obj = va_arg(*vargs, PyObject *);
         assert(obj && _PyUnicode_CHECK(obj));
 
-        if (_PyUnicodeWriter_WriteStr(writer, obj) == -1)
+        if (unicode_fromformat_write_str(writer, obj, width, precision) == -1)
             return NULL;
         break;
     }
@@ -2569,22 +2639,15 @@ unicode_fromformat_arg(_PyUnicodeWriter *writer,
     {
         PyObject *obj = va_arg(*vargs, PyObject *);
         const char *str = va_arg(*vargs, const char *);
-        PyObject *str_obj;
-        assert(obj || str);
         if (obj) {
             assert(_PyUnicode_CHECK(obj));
-            if (_PyUnicodeWriter_WriteStr(writer, obj) == -1)
+            if (unicode_fromformat_write_str(writer, obj, width, precision) == -1)
                 return NULL;
         }
         else {
-            str_obj = PyUnicode_DecodeUTF8Stateful(str, strlen(str), "replace", NULL);
+            assert(str != NULL);
-            if (!str_obj)
+            if (unicode_fromformat_write_cstr(writer, str, width, precision) < 0)
                 return NULL;
-            if (_PyUnicodeWriter_WriteStr(writer, str_obj) == -1) {
-                Py_DECREF(str_obj);
-                return NULL;
-            }
-            Py_DECREF(str_obj);
         }
         break;
     }
@@ -2597,7 +2660,7 @@ unicode_fromformat_arg(_PyUnicodeWriter *writer,
         str = PyObject_Str(obj);
         if (!str)
             return NULL;
-        if (_PyUnicodeWriter_WriteStr(writer, str) == -1) {
+        if (unicode_fromformat_write_str(writer, str, width, precision) == -1) {
             Py_DECREF(str);
             return NULL;
         }
@@ -2613,7 +2676,7 @@ unicode_fromformat_arg(_PyUnicodeWriter *writer,
         repr = PyObject_Repr(obj);
         if (!repr)
             return NULL;
-        if (_PyUnicodeWriter_WriteStr(writer, repr) == -1) {
+        if (unicode_fromformat_write_str(writer, repr, width, precision) == -1) {
             Py_DECREF(repr);
             return NULL;
         }
@@ -2629,7 +2692,7 @@ unicode_fromformat_arg(_PyUnicodeWriter *writer,
         ascii = PyObject_ASCII(obj);
         if (!ascii)
             return NULL;
-        if (_PyUnicodeWriter_WriteStr(writer, ascii) == -1) {
+        if (unicode_fromformat_write_str(writer, ascii, width, precision) == -1) {
             Py_DECREF(ascii);
             return NULL;
         }