From 7a3e091c1c9cc9ae6e34279c7c99c9989afd8894 Mon Sep 17 00:00:00 2001
From: Mike Bayer <mike_mp@zzzcomputing.com>
Date: Wed, 24 Sep 2014 15:04:53 -0400
Subject: Unwrap DialectFunctionDispatcher from itself.

The DialectFunctionDispatcher.dispatch_for() decorator method
necessarily returns the dispatcher itself and not the
decorated function, so that the object can continue to be
re-used even if the function name is the same as that of the
dispatcher.   In order to support a single function being
wrapped by the dispatcher multiple times with different
criteria, dispatch_for() will now check for the last function
wrapped and use that.

Change-Id: I331670d9b76ae30e7a666648e7e2d4c72641c9ff
Closes-Bug: #1373568
---
 oslo/db/sqlalchemy/utils.py    |  3 +++
 tests/sqlalchemy/test_utils.py | 35 +++++++++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+)

diff --git a/oslo/db/sqlalchemy/utils.py b/oslo/db/sqlalchemy/utils.py
index adc9bef..71cd1ea 100644
--- a/oslo/db/sqlalchemy/utils.py
+++ b/oslo/db/sqlalchemy/utils.py
@@ -899,6 +899,9 @@ class DialectFunctionDispatcher(object):
     def dispatch_for(self, expr):
         def decorate(fn):
             dbname, driver = self._parse_dispatch(expr)
+            if fn is self:
+                fn = fn._last
+            self._last = fn
             self._register(expr, dbname, driver, fn)
             return self
         return decorate
diff --git a/tests/sqlalchemy/test_utils.py b/tests/sqlalchemy/test_utils.py
index a4cd3f2..742cd38 100644
--- a/tests/sqlalchemy/test_utils.py
+++ b/tests/sqlalchemy/test_utils.py
@@ -990,6 +990,41 @@ class TestDialectFunctionDispatcher(test_base.BaseTestCase):
             callable_fn.mock_calls
         )
 
+    def test_multiple_nesting(self):
+        callable_fn = mock.Mock(
+            default=mock.Mock(return_value=None),
+            mysql=mock.Mock(return_value=None)
+        )
+
+        dispatcher = utils.dispatch_for_dialect("*", multiple=True)(
+            callable_fn.default)
+
+        dispatcher = dispatcher.dispatch_for("mysql+mysqlconnector")(
+            dispatcher.dispatch_for("mysql+mysqldb")(
+                callable_fn.mysql
+            )
+        )
+
+        mysqldb_url = sqlalchemy.engine.url.make_url("mysql+mysqldb://")
+        mysqlconnector_url = sqlalchemy.engine.url.make_url(
+            "mysql+mysqlconnector://")
+        sqlite_url = sqlalchemy.engine.url.make_url("sqlite://")
+
+        dispatcher(mysqldb_url, 1)
+        dispatcher(mysqlconnector_url, 2)
+        dispatcher(sqlite_url, 3)
+
+        self.assertEqual(
+            [
+                mock.call.mysql(mysqldb_url, 1),
+                mock.call.default(mysqldb_url, 1),
+                mock.call.mysql(mysqlconnector_url, 2),
+                mock.call.default(mysqlconnector_url, 2),
+                mock.call.default(sqlite_url, 3)
+            ],
+            callable_fn.mock_calls
+        )
+
     def test_single_retval(self):
         dispatcher, callable_fn = self._single_fixture()
         callable_fn.mysql_mysqldb.return_value = 5
-- 
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