348: If no keys are passed to DefaultFrom.__init__(), the keys from callback.func_code.co_varnames are used; updated DefaultFrom unit tests to test this usage

ipalib/frontend.py

@@ -61,12 +61,16 @@ class DefaultFrom(plugable.ReadOnly):
         :param callback: The callable to call when all ``keys`` are present.
         :param keys: The keys used to map from keyword to position arguments.
         """
-        assert callable(callback), 'not a callable: %r' % callback
-        assert len(keys) > 0, 'must have at least one key'
-        for key in keys:
-            assert type(key) is str, 'not an str: %r' % key
+        if not callable(callback):
+            raise TypeError('callback must be callable; got %r' % callback)
         self.callback = callback
-        self.keys = keys
+        if len(keys) == 0:
+            self.keys = callback.func_code.co_varnames
+        else:
+            self.keys = keys
+        for key in self.keys:
+            if type(key) is not str:
+                raise_TypeError(key, str, 'keys')
         lock(self)
 
     def __call__(self, **kw):
@@ -77,11 +81,11 @@ class DefaultFrom(plugable.ReadOnly):
         """
         vals = tuple(kw.get(k, None) for k in self.keys)
         if None in vals:
-            return None
+            return
         try:
             return self.callback(*vals)
-        except Exception:
-            return None
+        except StandardError:
+            pass
 
 
 def parse_param_spec(spec):

ipalib/tests/test_frontend.py

@@ -89,6 +89,9 @@ class test_DefaultFrom(ClassChecker):
         o = self.cls(callback, *keys)
         assert read_only(o, 'callback') is callback
         assert read_only(o, 'keys') == keys
+        lam = lambda first, last: first[0] + last
+        o = self.cls(lam)
+        assert read_only(o, 'keys') == ('first', 'last')
 
     def test_call(self):
         """
@@ -109,6 +112,10 @@ class test_DefaultFrom(ClassChecker):
             kw_copy = dict(kw)
             del kw_copy[key]
             assert o(**kw_copy) is None
+        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
 
 
 def test_parse_param_spec():