From 80a5be1d84689a680900ff4900acb2a39ec6d2a8 Mon Sep 17 00:00:00 2001
From: Richard Oudkerk <shibturn@gmail.com>
Date: Sun, 23 Mar 2014 12:30:54 +0000
Subject: [PATCH] Issue #20980: Stop wrapping exception when using ThreadPool.

---
 Lib/multiprocessing/managers.py   | 11 ++++++++---
 Lib/multiprocessing/pool.py       | 12 +++++++++---
 Lib/test/_test_multiprocessing.py | 11 +++++++++++
 Misc/NEWS                         |  2 ++
 4 files changed, 30 insertions(+), 6 deletions(-)

diff --git a/Lib/multiprocessing/managers.py b/Lib/multiprocessing/managers.py
index cc87d36612..66d46fcc2a 100644
--- a/Lib/multiprocessing/managers.py
+++ b/Lib/multiprocessing/managers.py
@@ -1077,17 +1077,22 @@ ArrayProxy = MakeProxyType('ArrayProxy', (
     ))
 
 
-PoolProxy = MakeProxyType('PoolProxy', (
+BasePoolProxy = MakeProxyType('PoolProxy', (
     'apply', 'apply_async', 'close', 'imap', 'imap_unordered', 'join',
-    'map', 'map_async', 'starmap', 'starmap_async', 'terminate'
+    'map', 'map_async', 'starmap', 'starmap_async', 'terminate',
     ))
-PoolProxy._method_to_typeid_ = {
+BasePoolProxy._method_to_typeid_ = {
     'apply_async': 'AsyncResult',
     'map_async': 'AsyncResult',
     'starmap_async': 'AsyncResult',
     'imap': 'Iterator',
     'imap_unordered': 'Iterator'
     }
+class PoolProxy(BasePoolProxy):
+    def __enter__(self):
+        return self
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        self.terminate()
 
 #
 # Definition of SyncManager
diff --git a/Lib/multiprocessing/pool.py b/Lib/multiprocessing/pool.py
index 74d08756ed..8832a5ceb2 100644
--- a/Lib/multiprocessing/pool.py
+++ b/Lib/multiprocessing/pool.py
@@ -90,7 +90,8 @@ class MaybeEncodingError(Exception):
         return "<MaybeEncodingError: %s>" % str(self)
 
 
-def worker(inqueue, outqueue, initializer=None, initargs=(), maxtasks=None):
+def worker(inqueue, outqueue, initializer=None, initargs=(), maxtasks=None,
+           wrap_exception=False):
     assert maxtasks is None or (type(maxtasks) == int and maxtasks > 0)
     put = outqueue.put
     get = inqueue.get
@@ -117,7 +118,8 @@ def worker(inqueue, outqueue, initializer=None, initargs=(), maxtasks=None):
         try:
             result = (True, func(*args, **kwds))
         except Exception as e:
-            e = ExceptionWithTraceback(e, e.__traceback__)
+            if wrap_exception:
+                e = ExceptionWithTraceback(e, e.__traceback__)
             result = (False, e)
         try:
             put((job, i, result))
@@ -137,6 +139,8 @@ class Pool(object):
     '''
     Class which supports an async version of applying functions to arguments.
     '''
+    _wrap_exception = True
+
     def Process(self, *args, **kwds):
         return self._ctx.Process(*args, **kwds)
 
@@ -220,7 +224,8 @@ class Pool(object):
             w = self.Process(target=worker,
                              args=(self._inqueue, self._outqueue,
                                    self._initializer,
-                                   self._initargs, self._maxtasksperchild)
+                                   self._initargs, self._maxtasksperchild,
+                                   self._wrap_exception)
                             )
             self._pool.append(w)
             w.name = w.name.replace('Process', 'PoolWorker')
@@ -736,6 +741,7 @@ class IMapUnorderedIterator(IMapIterator):
 #
 
 class ThreadPool(Pool):
+    _wrap_exception = False
 
     @staticmethod
     def Process(*args, **kwds):
diff --git a/Lib/test/_test_multiprocessing.py b/Lib/test/_test_multiprocessing.py
index 8eb57fe87e..44d6c71e40 100644
--- a/Lib/test/_test_multiprocessing.py
+++ b/Lib/test/_test_multiprocessing.py
@@ -1810,6 +1810,17 @@ class _TestPool(BaseTestCase):
             self.assertIn('raise RuntimeError(123) # some comment',
                           f1.getvalue())
 
+    @classmethod
+    def _test_wrapped_exception(cls):
+        raise RuntimeError('foo')
+
+    def test_wrapped_exception(self):
+        # Issue #20980: Should not wrap exception when using thread pool
+        with self.Pool(1) as p:
+            with self.assertRaises(RuntimeError):
+                p.apply(self._test_wrapped_exception)
+
+
 def raising():
     raise KeyError("key")
 
diff --git a/Misc/NEWS b/Misc/NEWS
index 2f9afb9698..5ec11eb8a8 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -21,6 +21,8 @@ Core and Builtins
 Library
 -------
 
+- Issue #20980: Stop wrapping exception when using ThreadPool.
+
 - Issue #20990: Fix issues found by pyflakes for multiprocessing.
 
 - Issue #21015: SSL contexts will now automatically select an elliptic
-- 
2.50.1