pythongh-80480 Deprecate array's 'u' type code

Author: hugovk

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 +205,11 @@ 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 (:gh:`57281`)
 
 
 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"")

Lib/test/test_buffer.py

@@ -3209,10 +3209,11 @@ def test_memoryview_compare_special_cases(self):
         self.assertNotEqual(memoryview(nd), nd)
 
         # Depends on issue #15625: the struct module does not understand 'u'.
-        a = array.array('u', 'xyz')
-        v = memoryview(a)
-        self.assertNotEqual(a, v)
-        self.assertNotEqual(v, a)
+        with self.assertRaises(DeprecationWarning):
+            a = array.array('u', 'xyz')
+            v = memoryview(a)
+            self.assertNotEqual(a, v)
+            self.assertNotEqual(v, a)
 
         # Some ctypes format strings are unknown to the struct module.
         if ctypes:

Lib/test/test_csv.py

@@ -882,14 +882,15 @@ def test_float_write(self):
 
     def test_char_write(self):
         import array, string
-        a = array.array('u', string.ascii_letters)
-
-        with TemporaryFile("w+", encoding="utf-8", newline='') as fileobj:
-            writer = csv.writer(fileobj, dialect="excel")
-            writer.writerow(a)
-            expected = ",".join(a)+"\r\n"
-            fileobj.seek(0)
-            self.assertEqual(fileobj.read(), expected)
+            with self.assertRaises(DeprecationWarning):
+            a = array.array('u', string.ascii_letters)
+
+            with TemporaryFile("w+", encoding="utf-8", newline='') as fileobj:
+                writer = csv.writer(fileobj, dialect="excel")
+                writer.writerow(a)
+                expected = ",".join(a)+"\r\n"
+                fileobj.seek(0)
+                self.assertEqual(fileobj.read(), expected)
 
 class TestDialectValidity(unittest.TestCase):
     def test_quoting(self):

Lib/test/test_re.py

@@ -1520,11 +1520,16 @@ def test_bug_6561(self):
     def test_empty_array(self):
         # SF buf 1647541
         import array
-        for typecode in 'bBuhHiIlLfd':
+        for typecode in 'bBhHiIlLfd':
             a = array.array(typecode)
             self.assertIsNone(re.compile(b"bla").match(a))
             self.assertEqual(re.compile(b"").match(a).groups(), ())
 
+        with self.assertWarns(DeprecationWarning):
+            a = array.array('u')
+        self.assertIsNone(re.compile(b"bla").match(a))
+        self.assertEqual(re.compile(b"").match(a).groups(), ())
+
     def test_inline_flags(self):
         # Bug #1700
         upper_char = '\u1ea0' # Latin Capital Letter A with Dot Below

Modules/arraymodule.c

@@ -2625,6 +2625,15 @@ array_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
         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 (initial && c != 'u') {
         if (PyUnicode_Check(initial)) {
             PyErr_Format(PyExc_TypeError, "cannot use a str to initialize "