From 62a7b879051f2029fe46618f8bf9a019bdb96845 Mon Sep 17 00:00:00 2001
From: Lisandro Dalcin <dalcinl@gmail.com>
Date: Fri, 25 Oct 2019 12:22:41 +0300
Subject: [PATCH] mpi4py.futures: Fixes to support Python 3.8

---
 demo/futures/test_futures.py   |  7 +++++--
 src/mpi4py/futures/__init__.py | 10 ++++++++++
 src/mpi4py/futures/_base.py    | 25 +++++++++++++++++++++++--
 3 files changed, 38 insertions(+), 4 deletions(-)

diff --git a/demo/futures/test_futures.py b/demo/futures/test_futures.py
index 925544d..7e03003 100644
--- a/demo/futures/test_futures.py
+++ b/demo/futures/test_futures.py
@@ -1157,7 +1157,9 @@ class ThenTest(unittest.TestCase):
         def transform(a):
             try:
                 f = chain.pop(0)
-                f.set_result(transform(a))
+                r = transform(a)
+                f.__init__()
+                f.set_result(r)
                 return f
             except IndexError:
                 return 42
@@ -1176,7 +1178,8 @@ class ThenTest(unittest.TestCase):
         self.assert_(new_f.exception())
         with self.assertRaises(RuntimeError) as catcher:
             new_f.result()
-        assert 'Circular future chain detected' in catcher.exception.args[0]
+        self.assert_('Circular future chain detected'
+                     in catcher.exception.args[0])
 
 
 SKIP_POOL_TEST = False
diff --git a/src/mpi4py/futures/__init__.py b/src/mpi4py/futures/__init__.py
index d8c00bc..0518d7a 100644
--- a/src/mpi4py/futures/__init__.py
+++ b/src/mpi4py/futures/__init__.py
@@ -15,6 +15,14 @@ try:
         wait,
         as_completed,
     )
+    try:  # Python 3.7
+        from concurrent.futures import BrokenExecutor
+    except ImportError:  # pragma: no cover
+        BrokenExecutor = RuntimeError
+    try:  # Python 3.8
+        from concurrent.futures import InvalidStateError
+    except ImportError:  # pragma: no cover
+        InvalidStateError = CancelledError.__base__
 except ImportError:  # pragma: no cover
     from ._base import (
         FIRST_COMPLETED,
@@ -22,6 +30,8 @@ except ImportError:  # pragma: no cover
         ALL_COMPLETED,
         CancelledError,
         TimeoutError,
+        InvalidStateError,
+        BrokenExecutor,
         Future,
         Executor,
         wait,
diff --git a/src/mpi4py/futures/_base.py b/src/mpi4py/futures/_base.py
index cfbd2c0..3eaa512 100644
--- a/src/mpi4py/futures/_base.py
+++ b/src/mpi4py/futures/_base.py
@@ -1,4 +1,4 @@
-# Backport of concurrent.futures._base from Python 3.7
+# Backport of concurrent.futures._base from Python 3.8
 # pylint: skip-file
 
 # Copyright 2009 Brian Quinlan. All Rights Reserved.
@@ -61,6 +61,10 @@ class TimeoutError(Error):
     """The operation exceeded the given deadline."""
     pass
 
+class InvalidStateError(Error):
+    """The operation is not allowed in this state."""
+    pass
+
 class _Waiter(object):
     """Provides the event that wait() and as_completed() block on."""
     def __init__(self):
@@ -414,7 +418,14 @@ class Future(object):
             if self._state not in [CANCELLED, CANCELLED_AND_NOTIFIED, FINISHED]:
                 self._done_callbacks.append(fn)
                 return
-        fn(self)
+        try:
+            fn(self)
+        except Exception:
+            LOGGER.exception('exception calling callback for %r', self)
+        except BaseException:
+            raise
+        except:  # old-style exception objects
+            LOGGER.exception('exception calling callback for %r', self)
 
     def result(self, timeout=None):
         """Return the result of the call that the future represents.
@@ -527,6 +538,8 @@ class Future(object):
         Should only be used by Executor implementations and unit tests.
         """
         with self._condition:
+            if self._state in {CANCELLED, CANCELLED_AND_NOTIFIED, FINISHED}:
+                raise InvalidStateError('{}: {!r}'.format(self._state, self))
             self._result = result
             self._state = FINISHED
             for waiter in self._waiters:
@@ -540,6 +553,8 @@ class Future(object):
         Should only be used by Executor implementations and unit tests.
         """
         with self._condition:
+            if self._state in {CANCELLED, CANCELLED_AND_NOTIFIED, FINISHED}:
+                raise InvalidStateError('{}: {!r}'.format(self._state, self))
             self._exception = exception
             self._state = FINISHED
             for waiter in self._waiters:
@@ -625,3 +640,9 @@ class Executor(object):
     def __exit__(self, exc_type, exc_val, exc_tb):
         self.shutdown(wait=True)
         return False
+
+
+class BrokenExecutor(RuntimeError):
+    """
+    Raised when a executor has become non-functional after a severe failure.
+    """
-- 
2.10.5