gh-80480 Emit DeprecationWarning for array's 'u' type code

Doc/library/array.rst

@@ -55,7 +55,7 @@ Notes:
       ``Py_UNICODE``. This change doesn't affect its behavior because
       ``Py_UNICODE`` is alias of ``wchar_t`` since Python 3.3.
 
-   .. deprecated-removed:: 3.3 4.0
+   .. deprecated-removed:: 3.3 3.14
 
 
 The actual representation of values is determined by the machine architecture

Doc/whatsnew/3.12.rst

@@ -205,8 +205,13 @@ Pending Removal in Python 3.14
 
   (Contributed by Jason R. Coombs and Hugo van Kemenade in :gh:`93963`.)
 
+APIs:
+
 * Creating :c:data:`immutable types <Py_TPFLAGS_IMMUTABLETYPE>` with mutable
-  bases using the C API.
+  bases using the C API (:gh:`95388`)
+* :mod:`array`'s ``'u'`` format code, deprecated in docs since Python 3.3,
+  emits :exc:`DeprecationWarning` since 3.12
+  (contributed by Hugo van Kemenade in :gh:`80480`)
 
 
 Pending Removal in Future Versions

Lib/test/test_array.py

@@ -13,11 +13,14 @@
 import operator
 import struct
 import sys
+import warnings
 
 import array
 from array import _array_reconstructor as array_reconstructor
 
-sizeof_wchar = array.array('u').itemsize
+with warnings.catch_warnings():
+    warnings.simplefilter('ignore', DeprecationWarning)
+    sizeof_wchar = array.array('u').itemsize
 
 
 class ArraySubclass(array.array):
@@ -93,8 +96,16 @@ def test_empty(self):
 UTF32_LE = 20
 UTF32_BE = 21
 
+
 class ArrayReconstructorTest(unittest.TestCase):
 
+    def setUp(self):
+        warnings.filterwarnings(
+            "ignore",
+            message="The 'u' type code is deprecated and "
+                    "will be removed in Python 3.14",
+            category=DeprecationWarning)
+
     def test_error(self):
         self.assertRaises(TypeError, array_reconstructor,
                           "", "b", 0, b"")
@@ -1205,6 +1216,15 @@ def test_issue17223(self):
         self.assertRaises(ValueError, a.tounicode)
         self.assertRaises(ValueError, str, a)
 
+    def test_typecode_u_deprecation(self):
+        with warnings.catch_warnings(record=True) as w:
+            warnings.simplefilter("always", DeprecationWarning)
+            array.array("u")
+        self.assertGreaterEqual(len(w), 1)
+        for warning in w:
+            self.assertIs(warning.category, DeprecationWarning)
+
+
 class NumberTest(BaseTest):
 
     def test_extslice(self):

Lib/test/test_buffer.py

@@ -23,6 +23,7 @@
 import sys, array, io, os
 from decimal import Decimal
 from fractions import Fraction
+from test.support import warnings_helper
 
 try:
     from _testbuffer import *
@@ -3174,6 +3175,7 @@ def cmptest(testcase, a, b, m, singleitem):
                             self.assertEqual(m.tobytes(), a.tobytes())
                             cmptest(self, a, b, m, singleitem)
 
+    @warnings_helper.ignore_warnings(category=DeprecationWarning)  # gh-80480 array('u')
     def test_memoryview_compare_special_cases(self):
 
         a = array.array('L', [1, 2, 3])

Lib/test/test_csv.py

@@ -880,6 +880,7 @@ def test_float_write(self):
             fileobj.seek(0)
             self.assertEqual(fileobj.read(), expected)
 
+    @warnings_helper.ignore_warnings(category=DeprecationWarning)  # gh-80480 array('u')
     def test_char_write(self):
         import array, string
         a = array.array('u', string.ascii_letters)

Lib/test/test_re.py

@@ -1,7 +1,7 @@
 from test.support import (gc_collect, bigmemtest, _2G,
                           cpython_only, captured_stdout,
                           check_disallow_instantiation, is_emscripten, is_wasi,
-                          SHORT_TIMEOUT)
+                          warnings_helper, SHORT_TIMEOUT)
 import locale
 import re
 import string
@@ -1517,10 +1517,11 @@ def test_bug_6561(self):
         for x in not_decimal_digits:
             self.assertIsNone(re.match(r'^\d$', x))
 
+    @warnings_helper.ignore_warnings(category=DeprecationWarning)  # gh-80480 array('u')
     def test_empty_array(self):
         # SF buf 1647541
         import array
-        for typecode in 'bBuhHiIlLfd':
+        for typecode in 'bBhuHiIlLfd':
             a = array.array(typecode)
             self.assertIsNone(re.compile(b"bla").match(a))
             self.assertEqual(re.compile(b"").match(a).groups(), ())

Misc/NEWS.d/next/Library/2022-08-07-11-10-26.gh-issue-80480.IFccj3.rst

@@ -0,0 +1,2 @@
+Emit :exc:`DeprecationWarning` for :mod:`array`'s ``'u'`` type code,
+deprecated in docs since Python 3.3.

Modules/arraymodule.c

@@ -2620,6 +2620,15 @@ array_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
     if (!PyArg_ParseTuple(args, "C|O:array", &c, &initial))
         return NULL;
 
+    if (c == 'u') {
+        if (PyErr_WarnEx(PyExc_DeprecationWarning,
+                         "The 'u' type code is deprecated and "
+                         "will be removed in Python 3.14",
+                         1)) {
+            return NULL;
+        }
+    }
+
     if (PySys_Audit("array.__new__", "CO",
                     c, initial ? initial : Py_None) < 0) {
         return NULL;