Rename enginefacade.async to enginefacade.async_

Python 3.7 now makes "async" a keyword, so deprecate the
"async" name and replace with "async_".  Additionally,
use attribute name access only in order to implement and
test "async" as it won't work under Python 3.7.

Closes-Bug: #1775866
Change-Id: Ifb2c59c2cfbd615b04570b31fcfe868f4ffea3c6

2 files changed, 39 insertions, 6 deletions

diff --git a/oslo_db/sqlalchemy/enginefacade.py b/oslo_db/sqlalchemy/enginefacade.py
index 2b9f81e..481e166 100644
--- a/oslo_db/sqlalchemy/enginefacade.py
+++ b/oslo_db/sqlalchemy/enginefacade.py
@@ -17,6 +17,7 @@ import operator
 import threading
 import warnings
 
+import debtcollector.moves
 import debtcollector.removals
 import debtcollector.renames
 from oslo_config import cfg
@@ -965,7 +966,7 @@ class _TransactionContextManager(object):
         return self._clone(connection=True)
 
     @property
-    def async(self):
+    def async_(self):
         """Modifier to set a READER operation to ASYNC_READER."""
 
         if self._mode is _WRITER:
@@ -1049,6 +1050,17 @@ class _TransactionContextManager(object):
                 transaction_contexts_by_thread.current = restore
 
 
+@property
+@debtcollector.moves.moved_property("async_")
+def async_compat(self):
+    return self.async_
+
+setattr(
+    _TransactionContextManager,
+    "async", async_compat
+)
+
+
 def _context_descriptor(attr=None):
     getter = operator.attrgetter(attr)
 
diff --git a/oslo_db/tests/sqlalchemy/test_enginefacade.py b/oslo_db/tests/sqlalchemy/test_enginefacade.py
index ced9483..cab7547 100644
--- a/oslo_db/tests/sqlalchemy/test_enginefacade.py
+++ b/oslo_db/tests/sqlalchemy/test_enginefacade.py
@@ -15,6 +15,7 @@ import contextlib
 import copy
 import fixtures
 import pickle
+import sys
 import warnings
 
 import mock
@@ -607,7 +608,7 @@ class MockFacadeTest(oslo_test_base.BaseTestCase):
 
     def test_async_on_writer_raises(self):
         exc = self.assertRaises(
-            TypeError, getattr, enginefacade.writer, "async"
+            TypeError, getattr, enginefacade.writer, "async_"
         )
         self.assertEqual(
             "Setting async on a WRITER makes no sense",
@@ -626,7 +627,7 @@ class MockFacadeTest(oslo_test_base.BaseTestCase):
     def test_reader_nested_in_async_reader_raises(self):
         context = oslo_context.RequestContext()
 
-        @enginefacade.reader.async
+        @enginefacade.reader.async_
         def go1(context):
             context.session.execute("test1")
             go2(context)
@@ -647,7 +648,7 @@ class MockFacadeTest(oslo_test_base.BaseTestCase):
     def test_reader_allow_async_nested_in_async_reader(self):
         context = oslo_context.RequestContext()
 
-        @enginefacade.reader.async
+        @enginefacade.reader.async_
         def go1(context):
             context.session.execute("test1")
             go2(context)
@@ -701,7 +702,7 @@ class MockFacadeTest(oslo_test_base.BaseTestCase):
     def test_writer_nested_in_async_reader_raises(self):
         context = oslo_context.RequestContext()
 
-        @enginefacade.reader.async
+        @enginefacade.reader.async_
         def go1(context):
             context.session.execute("test1")
             go2(context)
@@ -741,10 +742,30 @@ class MockFacadeTest(oslo_test_base.BaseTestCase):
                 with self._assert_writer_session(makers) as session:
                     session.execute("test2")
 
+    def test_deprecated_async_reader_name(self):
+        if sys.version_info >= (3, 7):
+            self.skipTest("Test only runs on Python < 3.7")
+
+        context = oslo_context.RequestContext()
+
+        old = getattr(enginefacade.reader, "async")
+
+        @old
+        def go1(context):
+            context.session.execute("test1")
+
+        go1(context)
+
+        with self._assert_engines() as engines:
+            with self._assert_makers(engines) as makers:
+                with self._assert_async_reader_session(
+                        makers, assert_calls=False) as session:
+                    session.execute("test1")
+
     def test_async_reader_then_reader_ok(self):
         context = oslo_context.RequestContext()
 
-        @enginefacade.reader.async
+        @enginefacade.reader.async_
         def go1(context):
             context.session.execute("test1")