From 4f7ceedb8a7742e52b0436a4160c7c44665a2597 Mon Sep 17 00:00:00 2001
From: Alex Gr?nholm <alex.gronholm@nextday.fi>
Date: Mon, 8 Sep 2014 06:46:34 +0300
Subject: Added the set_exception_info() and exception_info() methods to Future
 which provide the missing  traceback information on Python 2.x

---
 concurrent/futures/_base.py | 47 +++++++++++++++++++++++++++++++++++++--------
 1 file changed, 39 insertions(+), 8 deletions(-)

(limited to 'concurrent/futures/_base.py')

diff --git a/concurrent/futures/_base.py b/concurrent/futures/_base.py
index 8ed69b7..6f0c0f3 100644
--- a/concurrent/futures/_base.py
+++ b/concurrent/futures/_base.py
@@ -6,6 +6,8 @@ import logging
 import threading
 import time
 
+from concurrent.futures._compat import reraise
+
 try:
     from collections import namedtuple
 except ImportError:
@@ -290,6 +292,7 @@ class Future(object):
         self._state = PENDING
         self._result = None
         self._exception = None
+        self._traceback = None
         self._waiters = []
         self._done_callbacks = []
 
@@ -353,7 +356,7 @@ class Future(object):
 
     def __get_result(self):
         if self._exception:
-            raise self._exception
+            reraise(self._exception, self._traceback)
         else:
             return self._result
 
@@ -405,8 +408,9 @@ class Future(object):
             else:
                 raise TimeoutError()
 
-    def exception(self, timeout=None):
-        """Return the exception raised by the call that the future represents.
+    def exception_info(self, timeout=None):
+        """Return a tuple of (exception, traceback) raised by the call that the
+        future represents.
 
         Args:
             timeout: The number of seconds to wait for the exception if the
@@ -422,22 +426,40 @@ class Future(object):
             TimeoutError: If the future didn't finish executing before the given
                 timeout.
         """
-
         with self._condition:
             if self._state in [CANCELLED, CANCELLED_AND_NOTIFIED]:
                 raise CancelledError()
             elif self._state == FINISHED:
-                return self._exception
+                return self._exception, self._traceback
 
             self._condition.wait(timeout)
 
             if self._state in [CANCELLED, CANCELLED_AND_NOTIFIED]:
                 raise CancelledError()
             elif self._state == FINISHED:
-                return self._exception
+                return self._exception, self._traceback
             else:
                 raise TimeoutError()
 
+    def exception(self, timeout=None):
+        """Return the exception raised by the call that the future represents.
+
+        Args:
+            timeout: The number of seconds to wait for the exception if the
+                future isn't done. If None, then there is no limit on the wait
+                time.
+
+        Returns:
+            The exception raised by the call that the future represents or None
+            if the call completed without raising.
+
+        Raises:
+            CancelledError: If the future was cancelled.
+            TimeoutError: If the future didn't finish executing before the given
+                timeout.
+        """
+        return self.exception_info(timeout)[0]
+
     # The following methods should only be used by Executors and in tests.
     def set_running_or_notify_cancel(self):
         """Mark the future as running or process any cancel notifications.
@@ -492,19 +514,28 @@ class Future(object):
             self._condition.notify_all()
         self._invoke_callbacks()
 
-    def set_exception(self, exception):
-        """Sets the result of the future as being the given exception.
+    def set_exception_info(self, exception, traceback):
+        """Sets the result of the future as being the given exception
+        and traceback.
 
         Should only be used by Executor implementations and unit tests.
         """
         with self._condition:
             self._exception = exception
+            self._traceback = traceback
             self._state = FINISHED
             for waiter in self._waiters:
                 waiter.add_exception(self)
             self._condition.notify_all()
         self._invoke_callbacks()
 
+    def set_exception(self, exception):
+        """Sets the result of the future as being the given exception.
+
+        Should only be used by Executor implementations and unit tests.
+        """
+        self.set_exception_info(exception, None)
+
 class Executor(object):
     """This is an abstract base class for concrete asynchronous executors."""
 
-- 
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