Fix false positive for catching-non-exception, for C based exceptions.

3 files changed, 45 insertions, 6 deletions

diff --git a/checkers/exceptions.py b/checkers/exceptions.py
index 9843001..175c77b 100644
--- a/checkers/exceptions.py
+++ b/checkers/exceptions.py
@@ -25,6 +25,23 @@ from pylint.checkers import BaseChecker
 from pylint.checkers.utils import is_empty, is_raising, check_messages
 from pylint.interfaces import IAstroidChecker
 
+def infer_bases(klass):
+    """ Fully infer the bases of the klass node.
+
+    This doesn't use .ancestors(), because we need
+    the non-inferable nodes (YES nodes),
+    which can't be retrieved from .ancestors()
+    """
+    for base in klass.bases:
+        try:
+            inferit = base.infer().next()
+        except astroid.InferenceError:
+            continue
+        if inferit is YES:
+            yield inferit
+        else:
+            for base in infer_bases(inferit):
+                yield base
 
 OVERGENERAL_EXCEPTIONS = ('Exception',)
 
@@ -214,9 +231,16 @@ class ExceptionsChecker(BaseChecker):
 
                     if (not inherit_from_std_ex(exc) and
                         exc.root().name != BUILTINS_NAME):
-                        self.add_message('catching-non-exception',
-                                         node=handler.type,
-                                         args=(exc.name, ))
+                        # try to see if the exception is based on a C based
+                        # exception, by infering all the base classes and
+                        # looking for inference errors
+                        bases = infer_bases(exc)
+                        fully_infered = not any(inferit is YES
+                                                for inferit in bases)
+                        if fully_infered:
+                            self.add_message('catching-non-exception',
+                                             node=handler.type,
+                                             args=(exc.name, ))
 
                 exceptions_classes += excs
 
diff --git a/test/input/func_catching_non_exception.py b/test/input/func_catching_non_exception.py
index e6bfc57..d8e0e2d 100644
--- a/test/input/func_catching_non_exception.py
+++ b/test/input/func_catching_non_exception.py
@@ -1,5 +1,6 @@
 """test non-exceptions catched
 """
+import socket
 
 __revision__ = 1
 
@@ -19,6 +20,16 @@ class MySecondGoodException(MyGoodException):
     """ custom 'exception' """
     pass
 
+class SkipException(socket.error):
+    """ This gave false positives for Python 2,
+    but not for Python 3, due to exception
+    hierarchy rewrite.
+    """
+
+class SecondSkipException(SkipException):
+    """ This too shouldn't give false
+    positives. """
+
 try:
     1 + 1
 except MyException:
@@ -39,3 +50,7 @@ try:
 except (MyGoodException, MySecondGoodException):
     print "should work"
 
+try:
+    1 + 3
+except (SkipException, SecondSkipException):
+    print "should work"
diff --git a/test/messages/func_catching_non_exception.txt b/test/messages/func_catching_non_exception.txt
index 9dc23eb..19f22ab 100644
--- a/test/messages/func_catching_non_exception.txt
+++ b/test/messages/func_catching_non_exception.txt
@@ -1,3 +1,3 @@
-E: 24: Catching an exception which doesn't inherit from BaseException: MyException
-E: 29: Catching an exception which doesn't inherit from BaseException: MyException
-E: 29: Catching an exception which doesn't inherit from BaseException: MySecondException
\ No newline at end of file
+E: 35: Catching an exception which doesn't inherit from BaseException: MyException
+E: 40: Catching an exception which doesn't inherit from BaseException: MyException
+E: 40: Catching an exception which doesn't inherit from BaseException: MySecondException
\ No newline at end of file