Fixed bug in DefaultFrom where impleied keys were using entire func_code.co_varnames instead of an approprate slice

ipalib/frontend.py

@@ -121,7 +121,8 @@ class DefaultFrom(plugable.ReadOnly):
             raise TypeError('callback must be callable; got %r' % callback)
         self.callback = callback
         if len(keys) == 0:
-            self.keys = callback.func_code.co_varnames
+            fc = callback.func_code
+            self.keys = fc.co_varnames[:fc.co_argcount]
         else:
             self.keys = keys
         for key in self.keys:

tests/test_ipalib/test_frontend.py

@@ -115,11 +115,21 @@ class test_DefaultFrom(ClassChecker):
             kw_copy = dict(kw)
             del kw_copy[key]
             assert o(**kw_copy) is None
+
+        # Test using implied keys:
         o = self.cls(lambda first, last: first[0] + last)
         assert o(first='john', last='doe') == 'jdoe'
         assert o(first='', last='doe') is None
         assert o(one='john', two='doe') is None
 
+        # Test that co_varnames slice is used:
+        def callback2(first, last):
+            letter = first[0]
+            return letter + last
+        o = self.cls(callback2)
+        assert o.keys == ('first', 'last')
+        assert o(first='john', last='doe') == 'jdoe'
+
 
 def test_parse_param_spec():
     """