Merge pull request #36 from Delgan/GH-35-fix-none-exception

Fix ValueError while formatting None-tuple exception

Author: cknd

stackprinter/__init__.py

@@ -310,8 +310,8 @@ def _is_exc_info(thing):
     if not isinstance(thing, tuple) or len(thing) != 3:
         return False
     a, b, c = thing
-    return (isinstance(a, type) and BaseException in a.mro() and
-            isinstance(b, BaseException))
+    return ((a is None or (isinstance(a, type) and BaseException in a.mro())) and
+            (b is None or (isinstance(b, BaseException))))
 
 def format_thread(thread, add_summary=False, **kwargs):
     try:

stackprinter/formatting.py

@@ -117,6 +117,9 @@ def format_exc_info(etype, evalue, tb, style='plaintext', add_summary='auto',
 
     see stackprinter.format() for docs about the keyword arguments
     """
+    if etype is None:
+        etype = type(None)
+
     msg = ''
     try:
         # First, recursively format any chained exceptions (exceptions

tests/test_formatting.py

@@ -47,4 +47,11 @@ def test_exception_formatting():
     print(msg_color)
 
 
+def test_none_tuple_formatting():
+    output = stackprinter.format((None, None, None))
+    assert output == "NoneType: None"
 
+
+def test_none_value_formatting():
+    output = stackprinter.format((TypeError, None, None))
+    assert output == "TypeError: None"