Allow requests to return futures (#18)

Author: gatesn

pyls_jsonrpc/endpoint.py

@@ -186,6 +186,10 @@ def _handle_request(self, msg_id, method, params):
             request_future = self._executor_service.submit(handler_result)
             self._client_request_futures[msg_id] = request_future
             request_future.add_done_callback(self._request_callback(msg_id))
+        elif isinstance(handler_result, futures.Future):
+            log.debug("Request handler is already a future %s", handler_result)
+            self._client_request_futures[msg_id] = handler_result
+            handler_result.add_done_callback(self._request_callback(msg_id))
         else:
             log.debug("Got result from synchronous request handler: %s", handler_result)
             self._consumer({

test/test_endpoint.py

@@ -1,5 +1,6 @@
 # Copyright 2018 Palantir Technologies, Inc.
 # pylint: disable=redefined-outer-name
+from concurrent import futures
 import time
 import mock
 import pytest
@@ -187,6 +188,26 @@ def test_consume_request(endpoint, consumer, dispatcher):
     })
 
 
+def test_consume_future_request(endpoint, consumer, dispatcher):
+    future_response = futures.ThreadPoolExecutor().submit(lambda: 1234)
+    handler = mock.Mock(return_value=future_response)
+    dispatcher['methodName'] = handler
+
+    endpoint.consume({
+        'jsonrpc': '2.0',
+        'id': MSG_ID,
+        'method': 'methodName',
+        'params': {'key': 'value'}
+    })
+
+    handler.assert_called_once_with({'key': 'value'})
+    await_assertion(lambda: consumer.assert_called_once_with({
+        'jsonrpc': '2.0',
+        'id': MSG_ID,
+        'result': 1234
+    }))
+
+
 def test_consume_async_request(endpoint, consumer, dispatcher):
     def _async_handler():
         return 1234