- workaround removal of nested() in py3k

1 files changed, 34 insertions, 0 deletions

diff --git a/lib/sqlalchemy/util/compat.py b/lib/sqlalchemy/util/compat.py
index 7f2238a13..972fda667 100644
--- a/lib/sqlalchemy/util/compat.py
+++ b/lib/sqlalchemy/util/compat.py
@@ -226,3 +226,37 @@ def with_metaclass(meta, *bases):
                 return type.__new__(cls, name, (), d)
             return meta(name, bases, d)
     return metaclass('temporary_class', None, {})
+
+
+from contextlib import contextmanager
+
+try:
+    from contextlib import nested
+except ImportError:
+    # removed in py3k, credit to mitsuhiko for
+    # workaround
+
+    @contextmanager
+    def nested(*managers):
+        exits = []
+        vars = []
+        exc = (None, None, None)
+        try:
+            for mgr in managers:
+                exit = mgr.__exit__
+                enter = mgr.__enter__
+                vars.append(enter())
+                exits.append(exit)
+            yield vars
+        except:
+            exc = sys.exc_info()
+        finally:
+            while exits:
+                exit = exits.pop()
+                try:
+                    if exit(*exc):
+                        exc = (None, None, None)
+                except:
+                    exc = sys.exc_info()
+            if exc != (None, None, None):
+                reraise(exc[0], exc[1], exc[2])