Merge pull request #835 from markshannon/python-compare-is-enum

Python: Fix 'comparison using is' query to account for enum members.

python/ql/src/Expressions/IsComparisons.qll

@@ -107,6 +107,20 @@ predicate invalid_portable_is_comparison(Compare comp, Cmpop op, ClassObject cls
         left.refersTo(obj) and right.refersTo(obj) and
         exists(ImmutableLiteral il | il.getLiteralObject() = obj)
     )
+    and
+    /* OK to use 'is' when comparing with a member of an enum */
+    not exists(Expr left, Expr right, AstNode origin |
+        comp.compares(left, op, right) and
+        enum_member(origin) |
+        left.refersTo(_, origin) or right.refersTo(_, origin)
+    )
 }
 
+private predicate enum_member(AstNode obj) {
+    exists(ClassObject cls, AssignStmt asgn |
+        cls.getASuperType().getName() = "Enum" |
+        cls.getPyClass() = asgn.getScope() and
+        asgn.getValue() = obj
+    )
+}
 

python/ql/test/query-tests/Expressions/eq/expressions_test.py

@@ -24,7 +24,7 @@
 
 
 
-#ODASA-4519
+
 #OK as we are using identity tests for unique objects
 V2 = "v2"
 V3 = "v3"
@@ -85,3 +85,21 @@ def both_sides_known(zero_based="auto", query_id=False):
     if zero_based is False: # False positive here
         pass
 
+#Avoid depending on enum back port for Python 2 tests:
+class Enum(object):
+    pass
+
+class MyEnum(Enum):
+
+    memberA = None
+    memberB = 10
+    memberC = ("Hello", "World")
+
+def comp_enum(x):
+    if x is MyEnum.memberA:
+        return
+    if x is MyEnum.memberB:
+        return
+    if x is MyEnum.memberC:
+        return
+