Python: Add more tests for cls/self argument names

python/ql/test/query-tests/Functions/general/NonCls.expected

@@ -1,2 +1,3 @@
 | argument_names.py:17:5:17:24 | Function n_cmethod | Class methods or methods of a type deriving from type should have 'cls', rather than 'self', as their first argument. |
-| argument_names.py:32:5:32:20 | Function c_method | Class methods or methods of a type deriving from type should have 'cls', rather than 'y', as their first argument. |
+| argument_names.py:22:5:22:21 | Function n_cmethod2 | Class methods or methods of a type deriving from type should have 'cls' as their first argument. |
+| argument_names.py:37:5:37:20 | Function c_method | Class methods or methods of a type deriving from type should have 'cls', rather than 'y', as their first argument. |

python/ql/test/query-tests/Functions/general/NonSelf.expected

@@ -1,3 +1,4 @@
-| argument_names.py:45:5:45:20 | Function __init__ | Normal methods should have 'self', rather than 'x', as their first parameter. |
-| argument_names.py:48:5:48:20 | Function s_method | Normal methods should have 'self', rather than 'y', as their first parameter. |
+| argument_names.py:50:5:50:20 | Function __init__ | Normal methods should have 'self', rather than 'x', as their first parameter. |
+| argument_names.py:53:5:53:20 | Function s_method | Normal methods should have 'self', rather than 'y', as their first parameter. |
+| argument_names.py:56:5:56:20 | Function s_method2 | Normal methods should have at least one parameter (the first of which should be 'self'). |
 | om_test.py:71:5:71:19 | Function __repr__ | Normal methods should have at least one parameter (the first of which should be 'self'). |

python/ql/test/query-tests/Functions/general/argument_names.py

@@ -17,6 +17,11 @@ class Normal(object):
     def n_cmethod(self):
         pass
 
+    # not ok
+    @classmethod
+    def n_cmethod2():
+        pass
+
     # this is allowed because it has a decorator other than @classmethod
     @classmethod
     @id
@@ -48,6 +53,9 @@ class NonSelf(object):
     def s_method(y):
         pass
 
+    def s_method2():
+        pass
+
     def s_ok(self):
         pass
 
@@ -69,25 +77,32 @@ class NonSelf(object):
 
 #Possible FPs for non-self. ODASA-2439
 
-class C(object):
+class Acceptable1(object):
+    def _func(f):
+        return f
+    _func(x)
+
+class Acceptable2(object):
     def _func(f):
         return f
 
-    _func(x)
-
-    #or
     @_func
     def meth(self):
         pass
 
-
+# Handling methods defined in a different scope than the class it belongs to,
+# gets problmematic since we need to show the full-path from method definition
+# to actually adding it to the class. We tried to enable warnings for these in
+# September 2019, but ended up sticking to the decision from ODASA-2439 (where
+# results are both obvious and useful to the end-user).
 def dont_care(arg):
     pass
 
-class C(object):
+class Acceptable3(object):
 
     meth = dont_care
 
+# OK
 class Meta(type):
 
     #__new__ is an implicit class method, so the first arg is the metaclass