From 4a94989c06e8693be7bc3859418a0049d3ef4ae6 Mon Sep 17 00:00:00 2001
From: Laurent Peuch <cortex@worlddomination.be>
Date: Thu, 7 May 2020 22:22:42 +0200
Subject: [fix] metaclass conflict for class_deprecated

Actually the old compatibility code actually prevented this bug so back it up.
---
 logilab/common/deprecation.py | 20 +++++++++++++++++++-
 test/unittest_deprecation.py  | 11 +++++++++++
 2 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/logilab/common/deprecation.py b/logilab/common/deprecation.py
index b147b43..6edc71c 100644
--- a/logilab/common/deprecation.py
+++ b/logilab/common/deprecation.py
@@ -163,7 +163,25 @@ def callable_deprecated(reason=None, version=None, stacklevel=2):
 deprecated = callable_renamed(old_name="deprecated", new_function=callable_deprecated)
 
 
-class class_deprecated(type):
+def class_deprecated(old_name, parents, class_dict):
+    try:
+        return _class_deprecated(old_name, parents, clsdict)
+    except (NameError, TypeError):
+        # in case of conflicting metaclass situation
+        class DeprecatedClass(*parents):
+            def __init__(self, *args, **kwargs):
+                msg = class_dict.get("__deprecation_warning__", f"{old_name} is deprecated")
+                send_warning(
+                    msg,
+                    stacklevel=class_dict.get("__deprecation_warning_stacklevel__", 3),
+                    version=class_dict.get("__deprecation_warning_version__", None),
+                )
+                super(DeprecatedClass, self).__init__(*args, **kwargs)
+
+        return DeprecatedClass
+
+
+class _class_deprecated(type):
     """metaclass to print a warning on instantiation of a deprecated class"""
 
     def __call__(cls, *args, **kwargs):
diff --git a/test/unittest_deprecation.py b/test/unittest_deprecation.py
index 096978e..172b9fb 100644
--- a/test/unittest_deprecation.py
+++ b/test/unittest_deprecation.py
@@ -61,6 +61,17 @@ class RawInputTC(TestCase):
         self.assertEqual(self.messages,
                          ['[logilab.common] OldClass is deprecated, use AnyClass instead'])
 
+    def test_class_renamed_conflict_metaclass(self):
+        class SomeMetaClass(type):
+            pass
+
+        class AnyClass(metaclass=SomeMetaClass):
+            pass
+
+        # make sure the "metaclass conflict: the metaclass of a derived class # must be a
+        # (non-strict) subclass of the metaclasses of all its bases" exception won't be raised
+        deprecation.class_renamed("OldClass", AnyClass)
+
     def test_class_moved(self):
         class AnyClass(object):
             pass
-- 
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