Fixed Issue 42: Handled another type of exception and added testcase … (google#49)

Fixes issue google#42, falling back to str when json fails to handle circular references

Author: saurabhkpatel

fire/core.py

@@ -247,7 +247,7 @@ def _OneLineResult(result):
 
   try:
     return json.dumps(result)
-  except TypeError:
+  except (TypeError, ValueError):
     return str(result).replace('\n', ' ')
 
 

fire/core_test.py

@@ -33,6 +33,12 @@ def testOneLineResult(self):
     self.assertEqual(core._OneLineResult({}), '{}')  # pylint: disable=protected-access
     self.assertEqual(core._OneLineResult({'x': 'y'}), '{"x": "y"}')  # pylint: disable=protected-access
 
+
+  def testOneLineResultCircularRef(self):
+    circular_reference = tc.CircularReference()
+    self.assertEqual(core._OneLineResult(circular_reference.create()),  # pylint: disable=protected-access
+                     "{'y': {...}}")
+
   @mock.patch('fire.interact.Embed')
   def testInteractiveMode(self, mock_embed):
     core.Fire(tc.TypedProperties, 'alpha')

fire/test_components.py

@@ -206,3 +206,11 @@ def totally_empty(self):
 
   def nothing_printable(self):
     return {'__do_not_print_me': 1}
+
+
+class CircularReference(object):
+
+  def create(self):
+    x = {}
+    x['y'] = x
+    return x