Add H905 hacking check to ban eventlet usage

OpenStack projects are migrating away from eventlet.
Currently, each migrated project needs to implement their own eventlet
detection rules, leading to code duplication and inconsistent enforcement.

This change provides a standardized H905 hacking check that detects
eventlet imports across all OpenStack projects. The check is disabled
by default to avoid breaking unmigrated projects, but migrated projects
can simply enable it with "enable-extensions = H905" in their tox.ini
instead of maintaining custom eventlet detection code.

This eliminates the need to recreate this rule in each deliverable and
provides consistent eventlet removal enforcement across the ecosystem.

Assisted-By: Claude Code
Change-Id: I5b99df46098f022de5b316ca561c29cbfcdcb2a3
Signed-off-by: Hervé Beraud <[email protected]>

Author: 4383

HACKING.rst

@@ -33,6 +33,9 @@ General
 - [H105] Don't use author tags. We use version control instead.
 - [H106] Don't put vim configuration in source files (off by default).
 - [H904] Delay string interpolations at logging calls (off by default).
+- [H905] Do not import eventlet (off by default). Eventlet usage is being
+  removed from OpenStack projects as part of the async migration effort.
+  Use threading or asyncio instead.
 - Do not shadow a built-in or reserved word. Shadowing built -in or reserved
   words makes the code harder to understand. Example::
 
@@ -86,14 +89,15 @@ Real-world Import Order Examples
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 Example::
 
+  import asyncio
   import httplib
   import logging
   import random
   import StringIO
+  import threading
   import time
   import unittest
 
-  import eventlet
   import webob.exc
 
   import nova.api.ec2

hacking/checks/imports.py

@@ -15,6 +15,8 @@
 from hacking import core
 
 RE_RELATIVE_IMPORT = re.compile(r'^from\s*[.]')
+RE_EVENTLET_IMPORT = re.compile(
+    r'^\s*(?:import\s+eventlet(?:\s|$|\.)|from\s+eventlet(?:\s|$|\.))')
 
 
 @core.flake8ext
@@ -102,3 +104,25 @@ def hacking_import_alphabetical(logical_line, blank_before, previous_logical,
             if split_line[1] < split_previous[1]:
                 yield (0, "H306: imports not in alphabetical order (%s, %s)"
                        % (split_previous[1], split_line[1]))
+
+
+@core.flake8ext
+@core.off_by_default
+def hacking_no_eventlet(logical_line, noqa):
+    r"""Check that eventlet is not imported.
+
+    Eventlet is being removed from OpenStack projects as part of the
+    async migration effort. New code should use threading or asyncio instead.
+
+    Examples:
+    H905: import eventlet
+    H905: from eventlet import something
+    Okay: import asyncio
+    Okay: import threading
+    """
+    if noqa:
+        return
+
+    if RE_EVENTLET_IMPORT.match(logical_line):
+        yield (0, "H905: eventlet import detected. "
+                  "Eventlet is banned, use threading or asyncio instead.")

hacking/tests/checks/test_eventlet_imports.py

@@ -0,0 +1,44 @@
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+# implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import ddt
+
+from hacking.checks import imports
+from hacking import tests
+
+
+@ddt.ddt
+class ImportsTestCase(tests.TestCase):
+    """This tests hacking checks from the 'imports' group."""
+
+    @ddt.unpack
+    @ddt.data(
+        (True, 'import eventlet', None),
+        (True, 'from eventlet import monkey_patch', None),
+        (True, 'from eventlet.green import socket', None),
+        (True, '    import eventlet  # with indentation', None),
+        (True, '    from eventlet import something', None),
+        (False, 'import eventlet  # noqa', '# noqa'),
+        (False, 'import asyncio', None),
+        (False, 'import threading', None),
+        (False, 'from threading import Thread', None),
+        (False, 'import concurrent.futures', None),
+        (False, 'import some_other_module', None),
+        (False, 'import not_eventlet', None),
+        (False, 'from not_eventlet import something', None),
+    )
+    def test_H905_hacking_no_eventlet(self, should_fail, line, noqa):
+        if should_fail:
+            self.assertCheckFails(imports.hacking_no_eventlet, line, noqa)
+        else:
+            self.assertCheckPasses(imports.hacking_no_eventlet, line, noqa)

releasenotes/notes/add-eventlet-ban-hacking-check-H905-ef8a441d7ab85926.yaml

@@ -0,0 +1,7 @@
+---
+features:
+  - |
+    Added new hacking check ``H905`` to detect and ban ``eventlet`` usage in
+    OpenStack projects. This check supports the ongoing ``eventlet`` removal
+    effort across OpenStack as part of the async migration to ``threading``
+    and ``asyncio``.

setup.cfg

@@ -62,6 +62,7 @@ flake8.extension =
     H700 = hacking.checks.localization:hacking_localization_strings
     H903 = hacking.checks.other:hacking_no_cr
     H904 = hacking.checks.other:hacking_delayed_string_interpolation
+    H905 = hacking.checks.imports:hacking_no_eventlet
 
 [extras]
 pep257 =