From 8f56c90309db2353470a03650ee56cec5215ed44 Mon Sep 17 00:00:00 2001
From: Laurent Peuch <cortex@worlddomination.be>
Date: Thu, 16 Apr 2020 03:56:24 +0200
Subject: add depreciation.attribute_renamed

---
 logilab/common/deprecation.py | 45 +++++++++++++++++++++++++++++++++++++++++++
 test/unittest_deprecation.py  | 22 +++++++++++++++++++++
 2 files changed, 67 insertions(+)

diff --git a/logilab/common/deprecation.py b/logilab/common/deprecation.py
index 3cfdff0..d45424d 100644
--- a/logilab/common/deprecation.py
+++ b/logilab/common/deprecation.py
@@ -190,6 +190,51 @@ def moved(modpath, objname):
 moved.__doc__ = _defaultdeprecator.moved.__doc__
 
 
+def attribute_renamed(old_name, new_name):
+    """
+    class decorator to allow getting backward compatibility for renamed attributes.
+
+    >>> @attribute_renamed(old_name="old", new_name="new")
+    ... class SomeClass:
+    ...     def __init__(self):
+    ...         self.new = 42
+
+    >>> some_class = SomeClass()
+    >>> print(some_class.old)
+    sample.py:15: DeprecationWarning: SomeClass.old has been renamed and is deprecated, use SomeClass.new instead
+      print(some_class.old)
+    42
+    >>> some_class.old = 43
+    sample.py:16: DeprecationWarning: SomeClass.old has been renamed and is deprecated, use SomeClass.new instead
+      some_class.old = 43
+    >>> some_class.old == some_class.new
+    True
+    """
+    def _class_wrap(klass):
+        reason = (
+            f"{klass.__name__}.{old_name} has been renamed and is deprecated, use "
+            f"{klass.__name__}.{new_name} instead"
+        )
+
+        def _get_old(self):
+            warn(reason, DeprecationWarning, stacklevel=2)
+            return getattr(self, new_name)
+
+        def _set_old(self, value):
+            warn(reason, DeprecationWarning, stacklevel=2)
+            setattr(self, new_name, value)
+
+        def _del_old(self):
+            warn(reason, DeprecationWarning, stacklevel=2)
+            delattr(self, new_name)
+
+        setattr(klass, old_name, property(_get_old, _set_old, _del_old))
+
+        return klass
+
+    return _class_wrap
+
+
 def renamed(old_name, new_function):
     """use to tell that a callable has been renamed.
 
diff --git a/test/unittest_deprecation.py b/test/unittest_deprecation.py
index d82c2bc..7778325 100644
--- a/test/unittest_deprecation.py
+++ b/test/unittest_deprecation.py
@@ -71,6 +71,28 @@ class RawInputTC(TestCase):
         self.assertEqual(self.messages,
                          ['The function "any_func" is deprecated', 'message'])
 
+    def test_attribute_renamed(self):
+        @deprecation.attribute_renamed(old_name="old", new_name="new")
+        class SomeClass:
+            def __init__(self):
+                self.new = 42
+
+        some_class = SomeClass()
+        self.assertEqual(some_class.old, some_class.new)
+        self.assertEqual(self.messages,
+                         ['SomeClass.old has been renamed and is deprecated, use SomeClass.new '
+                          'instead'])
+
+        some_class.old = 43
+        self.assertEqual(some_class.old, 43)
+        self.assertEqual(some_class.old, some_class.new)
+
+        self.assertTrue(hasattr(some_class, "new"))
+        self.assertTrue(hasattr(some_class, "old"))
+        del some_class.old
+        self.assertFalse(hasattr(some_class, "new"))
+        self.assertFalse(hasattr(some_class, "old"))
+
     def test_renamed(self):
         def any_func():
             pass
-- 
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