Add a hacking rule for the setDaemon method

Add the following hacking rule.

* N372: Don't use the setDaemon method.
        Use the daemon attribute instead.

Change-Id: Idb45421205f76d2d3b0576bd0504d261ed249edd
Related-Bug: 1987191
Signed-off-by: Takashi Natsume <takanattie@gmail.com>

HACKING.rst

@@ -76,6 +76,7 @@ Nova Specific Commandments
   with eventlet patched code. Use nova.utils.ReaderWriterLock() instead.
 - [N370] Don't use or import six
 - [N371] You must explicitly import python's mock: ``from unittest import mock``
+- [N372] Don't use the setDaemon method. Use the daemon attribute instead.
 
 Creating Unit Tests
 -------------------

nova/hacking/checks.py

@@ -141,6 +141,8 @@ rwlock_re = re.compile(
     r"(?P<module_part>(oslo_concurrency\.)?(lockutils|fasteners))"
     r"\.ReaderWriterLock\(.*\)")
 six_re = re.compile(r"^(import six(\..*)?|from six(\..*)? import .*)$")
+# Regex for catching the setDaemon method
+set_daemon_re = re.compile(r"\.setDaemon\(")
 
 
 class BaseASTChecker(ast.NodeVisitor):
@@ -1078,3 +1080,22 @@ def import_stock_mock(logical_line):
             "N371: You must explicitly import python's mock: "
             "``from unittest import mock``"
         )
+
+
+@core.flake8ext
+def check_set_daemon(logical_line):
+    """Check for use of the setDaemon method of the threading.Thread class
+
+    The setDaemon method of the threading.Thread class has been deprecated
+    since Python 3.10. Use the daemon attribute instead.
+
+    See
+    https://docs.python.org/3.10/library/threading.html#threading.Thread.setDaemon
+    for details.
+
+    N372
+    """
+    res = set_daemon_re.search(logical_line)
+    if res:
+        yield (0, "N372: Don't use the setDaemon method. "
+                  "Use the daemon attribute instead.")

nova/tests/unit/test_hacking.py

@@ -1043,3 +1043,24 @@ class HackingTestCase(test.NoDBTestCase):
                     import unittest.mock
                """
         self._assert_has_no_errors(code, checks.import_stock_mock)
+
+    def test_check_set_daemon(self):
+        code = """
+                   self.setDaemon(True)
+                   worker.setDaemon(True)
+                   self._event_thread.setDaemon(True)
+                   mythread.setDaemon(False)
+                   self.thread.setDaemon(1)
+               """
+        errors = [(x + 1, 0, 'N372') for x in range(5)]
+        self._assert_has_errors(
+            code, checks.check_set_daemon, expected_errors=errors)
+
+        code = """
+                   self.setDaemon = True
+                   worker.setDaemonFlag(True)
+                   self._event_thread.resetDaemon(True)
+                   self.set.Daemon(True)
+                   self.thread.setdaemon(True)
+               """
+        self._assert_has_no_errors(code, checks.check_set_daemon)

tox.ini

@@ -351,6 +351,7 @@ extension =
   N369 = checks:check_lockutils_rwlocks
   N370 = checks:check_six
   N371 = checks:import_stock_mock
+  N372 = checks:check_set_daemon
 paths =
   ./nova/hacking