add test for #9588: false positive E1101 for augmented assignment

test/input/func_noerror_e1101_9588_base_attr_aug_assign.py

@@ -0,0 +1,39 @@
+# pylint: disable-msg=R0903
+"""
+False positive case of E1101:
+
+The error is triggered when the attribute set in the base class is
+modified with augmented assignment in a derived class.
+
+http://www.logilab.org/ticket/9588
+"""
+__revision__ = 0
+
+class BaseClass(object):
+    "The base class"
+    def __init__(self):
+        "Set an attribute."
+        self.e1101 = 1
+
+class FalsePositiveClass(BaseClass):
+    "The first derived class which triggers the false positive"
+    def __init__(self):
+        "Augmented assignment triggers E1101."
+        BaseClass.__init__(self)
+        self.e1101 += 1
+
+    def countup(self):
+        "Consequently this also triggers E1101."
+        self.e1101 += 1
+
+class NegativeClass(BaseClass):
+    "The second derived class, which does not trigger the error E1101"
+    def __init__(self):
+        "Ordinary assignment is OK."
+        BaseClass.__init__(self)
+        self.e1101 = self.e1101 + 1
+
+    def countup(self):
+        "No problem."
+        self.e1101 += 1
+