Catch unprintable application exception (#32208)

* Catch unprintable application exception

* fix sanity

* Remove some files

* Fix typo

src/python/grpcio/grpc/_server.py

@@ -499,8 +499,12 @@ def _call_behavior(
                     _abort(state, rpc_event.call, cygrpc.StatusCode.unknown,
                            b'RPC Aborted')
                 elif exception not in state.rpc_errors:
-                    details = 'Exception calling application: {}'.format(
-                        exception)
+                    try:
+                        details = 'Exception calling application: {}'.format(
+                            exception)
+                    except Exception:  # pylint: disable=broad-except
+                        details = 'Calling application raised unprintable Exception!'
+                        traceback.print_exc()
                     _LOGGER.exception(details)
                     _abort(state, rpc_event.call, cygrpc.StatusCode.unknown,
                            _common.encode(details))

src/python/grpcio_tests/tests/unit/_invocation_defects_test.py

@@ -27,6 +27,7 @@ _SERIALIZE_RESPONSE = lambda bytestring: bytestring * 3
 _DESERIALIZE_RESPONSE = lambda bytestring: bytestring[:len(bytestring) // 3]
 
 _UNARY_UNARY = '/test/UnaryUnary'
+_UNARY_UNARY_NESTED_EXCEPTION = '/test/UnaryUnaryNestedException'
 _UNARY_STREAM = '/test/UnaryStream'
 _STREAM_UNARY = '/test/StreamUnary'
 _STREAM_STREAM = '/test/StreamStream'
@@ -47,6 +48,10 @@ class _Handler(object):
             ),))
         return request
 
+    def handle_unary_unary_with_nested_exception(self, request,
+                                                 servicer_context):
+        raise test_control.NestedDefect()
+
     def handle_unary_stream(self, request, servicer_context):
         for _ in range(test_constants.STREAM_LENGTH):
             self._control.control()
@@ -128,6 +133,11 @@ class _GenericHandler(grpc.GenericRpcHandler):
                                   self._handler.handle_stream_stream)
         elif handler_call_details.method == _DEFECTIVE_GENERIC_RPC_HANDLER:
             return self._handler.defective_generic_rpc_handler()
+        elif handler_call_details.method == _UNARY_UNARY_NESTED_EXCEPTION:
+            return _MethodHandler(
+                False, False, None, None,
+                self._handler.handle_unary_unary_with_nested_exception, None,
+                None, None)
         else:
             return None
 
@@ -176,6 +186,10 @@ def _defective_handler_multi_callable(channel):
     return channel.unary_unary(_DEFECTIVE_GENERIC_RPC_HANDLER)
 
 
+def _defective_nested_exception_handler_multi_callable(channel):
+    return channel.unary_unary(_UNARY_UNARY_NESTED_EXCEPTION)
+
+
 class InvocationDefectsTest(unittest.TestCase):
     """Tests the handling of exception-raising user code on the client-side."""
 
@@ -260,6 +274,19 @@ class InvocationDefectsTest(unittest.TestCase):
         self.assertIs(grpc.StatusCode.UNKNOWN,
                       exception_context.exception.code())
 
+    def testNestedExceptionGenericRpcHandlerUnaryResponse(self):
+        request = b'\x07\x08'
+        multi_callable = _defective_nested_exception_handler_multi_callable(
+            self._channel)
+
+        with self.assertRaises(grpc.RpcError) as exception_context:
+            multi_callable(request,
+                           metadata=(('test',
+                                      'DefectiveGenericRpcHandlerUnary'),))
+
+        self.assertIs(grpc.StatusCode.UNKNOWN,
+                      exception_context.exception.code())
+
 
 if __name__ == '__main__':
     logging.basicConfig()

src/python/grpcio_tests/tests/unit/framework/common/test_control.py

@@ -26,6 +26,13 @@ class Defect(Exception):
   """
 
 
+class NestedDefect(Exception):
+    """Simulates a nested programming defect raised into in a system under test."""
+
+    def __str__(self):
+        raise Exception('Nested Exception')
+
+
 class Control(abc.ABC):
     """An object that accepts program control from a system under test.