Exclude some decorators

Author: joefarebrother

python/ql/src/Functions/MethodArgNames.qll

@@ -43,14 +43,24 @@ private predicate usedInInit(Function f, Class c) {
   )
 }
 
+/**
+ * Holds if `f` has no arguments, and also has a decorator.
+ * We assume that the decorator affect the method in such a way that a `self` parameter is unneeded.
+ */
+private predicate noArgsWithDecorator(Function f) {
+  not exists(f.getAnArg()) and
+  exists(f.getADecorator())
+}
+
 /** Holds if the first parameter of `f` should be named `self`. */
 predicate shouldBeSelf(Function f, Class c) {
   methodOfClass(f, c) and
   not isStaticmethod(f) and
   not isClassmethod(f) and
   not isMetaclass(c) and
   not isZopeInterface(c) and
-  not usedInInit(f, c)
+  not usedInInit(f, c) and
+  not noArgsWithDecorator(f)
 }
 
 /** Holds if the first parameter of `f` should be named `cls`. */

python/ql/test/query-tests/Functions/methodArgNames/parameter_names.py

@@ -120,7 +120,15 @@ def meth(arg):
 
 Z().meth(0)
 
+def weird_decorator(f):
+    def g(self):
+        return f()
+    return g 
 
+class B:
+    @weird_decorator
+    def f(): # allow no-arg functions with a decorator
+        pass
 
 # The `__init_subclass__` (introduced in Python 3.6)
 # and `__class_getitem__` (introduced in Python 3.7) methods are methods