- Fixed regression where using a ``functools.partial()`` with the event

system would cause a recursion overflow due to usage of inspect.getargspec()
on it in order to detect a legacy calling signature for certain events,
and apparently there's no way to do this with a partial object.  Instead
we skip the legacy check and assume the modern style; the check itself
now only occurs for the SessionEvents.after_bulk_update and
SessionEvents.after_bulk_delete events.  Those two events will require
the new signature style if assigned to a "partial" event listener.
[ticket:2905]

2 files changed, 10 insertions, 3 deletions

diff --git a/lib/sqlalchemy/event/attr.py b/lib/sqlalchemy/event/attr.py
index 690ebce08..f0fff5ca4 100644
--- a/lib/sqlalchemy/event/attr.py
+++ b/lib/sqlalchemy/event/attr.py
@@ -62,10 +62,15 @@ class _DispatchDescriptor(RefCollection):
         self._empty_listeners = weakref.WeakKeyDictionary()
 
     def _adjust_fn_spec(self, fn, named):
-        argspec = util.get_callable_argspec(fn, no_self=True)
         if named:
             fn = self._wrap_fn_for_kw(fn)
-        fn = legacy._wrap_fn_for_legacy(self, fn, argspec)
+        if self.legacy_signatures:
+            try:
+                argspec = util.get_callable_argspec(fn, no_self=True)
+            except ValueError:
+                pass
+            else:
+                fn = legacy._wrap_fn_for_legacy(self, fn, argspec)
         return fn
 
     def _wrap_fn_for_kw(self, fn):
diff --git a/lib/sqlalchemy/util/langhelpers.py b/lib/sqlalchemy/util/langhelpers.py
index 7e261e38f..105b64c6b 100644
--- a/lib/sqlalchemy/util/langhelpers.py
+++ b/lib/sqlalchemy/util/langhelpers.py
@@ -268,7 +268,9 @@ def get_callable_argspec(fn, no_self=False):
         return compat.ArgSpec(spec.args[1:], spec.varargs, spec.keywords, spec.defaults)
     elif hasattr(fn, '__func__'):
         return compat.inspect_getargspec(fn.__func__)
-    elif hasattr(fn, '__call__'):
+    elif hasattr(fn, '__call__') and \
+        not hasattr(fn.__call__, '__call__'):  # functools.partial does this;
+                                               # not much we can do
         return get_callable_argspec(fn.__call__)
     else:
         raise ValueError("Can't inspect function: %s" % fn)