Move deferToThread import outside of 'execute' function

Use a wrapper function instead of lambda + bool cast

Author: mfranciszkiewicz

golem/core/deferred.py

@@ -3,6 +3,7 @@
 
 from twisted.internet import defer
 from twisted.internet.task import deferLater
+from twisted.internet.threads import deferToThread
 from twisted.python.failure import Failure
 
 
@@ -11,9 +12,10 @@ def __init__(self, *fns) -> None:
         self._seq = list(fns)
 
     def execute(self) -> defer.Deferred:
-        from twisted.internet.threads import deferToThread
-        # The executed function cannot return a Deferred, hence the bool cast
-        return deferToThread(lambda *_: bool(self._execute()))
+        # The executed function cannot return a Deferred object
+        def wrapper():
+            self._execute()
+        return deferToThread(wrapper)
 
     @defer.inlineCallbacks
     def _execute(self) -> Any:

tests/golem/core/test_deferred.py

@@ -7,7 +7,7 @@
 from golem.core.deferred import chain_function, DeferredSeq
 
 
-@mock.patch('twisted.internet.threads.deferToThread', lambda x: succeed(x()))
+@mock.patch('golem.core.deferred.deferToThread', lambda x: succeed(x()))
 @mock.patch('twisted.internet.reactor', mock.Mock(), create=True)
 class TestDeferredSeq(unittest.TestCase):
 
@@ -21,13 +21,19 @@ def test_init_with_functions(self):
         ]
         assert DeferredSeq(*fns)._seq == fns
 
-    def test_execute_empty(self):
-        assert DeferredSeq().execute().result
+    @mock.patch('golem.core.deferred.DeferredSeq._execute')
+    def test_execute_empty(self, execute):
+        deferred_seq = DeferredSeq()
+        with mock.patch('golem.core.deferred.DeferredSeq._execute',
+                        wraps=deferred_seq._execute):
+            deferred_seq.execute()
+        assert execute.called
 
     def test_execute_functions(self):
         fn_1, fn_2 = mock.Mock(), mock.Mock()
         fns = [fn_1, fn_2]
-        assert DeferredSeq(*fns).execute().result
+
+        DeferredSeq(*fns).execute()
         assert fn_1.called
         assert fn_2.called
 
@@ -43,7 +49,7 @@ def def2t(f, *args, **kwargs) -> Deferred:
             except Exception as exc:  # pylint: disable=broad-except
                 return fail(exc)
 
-        with mock.patch('twisted.internet.threads.deferToThread', def2t):
+        with mock.patch('golem.core.deferred.deferToThread', def2t):
             DeferredSeq(fn_1, fn_2, fn_3, fn_4).execute()
 
         assert fn_1.called

tests/golem/task/test_rpc.py

@@ -124,7 +124,7 @@ def test_create_task(self, *_):
         def execute(f, *args, **kwargs):
             return defer.succeed(f(*args, **kwargs))
 
-        with mock.patch('twisted.internet.threads.deferToThread', execute):
+        with mock.patch('golem.core.deferred.deferToThread', execute):
             result = self.provider.create_task(t.to_dict())
         rpc.enqueue_new_task.assert_called()
         self.assertEqual(result, ('task_id', None))