gh-101865: Deprecate `co_lnotab` from code objects as per PEP 626 (#101866)

Co-authored-by: Oleg Iarygin <oleg@arhadthedev.net>

Doc/reference/datamodel.rst

@@ -991,7 +991,8 @@ Internal types
       the filename from which the code was compiled; :attr:`co_firstlineno` is
       the first line number of the function; :attr:`co_lnotab` is a string
       encoding the mapping from bytecode offsets to line numbers (for details
-      see the source code of the interpreter); :attr:`co_stacksize` is the
+      see the source code of the interpreter, is deprecated since 3.12
+      and may be removed in 3.14); :attr:`co_stacksize` is the
       required stack size; :attr:`co_flags` is an integer encoding a number
       of flags for the interpreter.
 

Doc/whatsnew/3.12.rst

@@ -622,6 +622,12 @@ Pending Removal in Python 3.14
   functions that have been deprecated since Python 2 but only gained a
   proper :exc:`DeprecationWarning` in 3.12. Remove them in 3.14.
 
+* Accessing ``co_lnotab`` was deprecated in :pep:`626` since 3.10
+  and was planned to be removed in 3.12
+  but it only got a proper :exc:`DeprecationWarning` in 3.12.
+  May be removed in 3.14.
+  (Contributed by Nikita Sobolev in :gh:`101866`.)
+
 * The *onerror* argument of :func:`shutil.rmtree` is deprecated in 3.12,
   and will be removed in 3.14.
 

Lib/test/test_code.py

@@ -338,6 +338,13 @@ class CodeTest(unittest.TestCase):
         new_code = code = func.__code__.replace(co_linetable=b'')
         self.assertEqual(list(new_code.co_lines()), [])
 
+    def test_co_lnotab_is_deprecated(self):  # TODO: remove in 3.14
+        def func():
+            pass
+
+        with self.assertWarns(DeprecationWarning):
+            func.__code__.co_lnotab
+
     def test_invalid_bytecode(self):
         def foo():
             pass

Misc/NEWS.d/next/Core and Builtins/2023-02-21-17-22-06.gh-issue-101865.fwrTOA.rst

@@ -0,0 +1,2 @@
+Deprecate ``co_lnotab`` in code objects, schedule it for removal in Python
+3.14

Objects/codeobject.c

@@ -1921,6 +1921,11 @@ static PyMemberDef code_memberlist[] = {
 static PyObject *
 code_getlnotab(PyCodeObject *code, void *closure)
 {
+    if (PyErr_WarnEx(PyExc_DeprecationWarning,
+                     "co_lnotab is deprecated, use co_lines instead.",
+                     1) < 0) {
+        return NULL;
+    }
     return decode_linetable(code);
 }