Write kw only arguments to pickle

cloudpickle/cloudpickle.py

@@ -591,6 +591,8 @@ def save_function_tuple(self, func):
             state['annotations'] = func.__annotations__
         if hasattr(func, '__qualname__'):
             state['qualname'] = func.__qualname__
+        if hasattr(func, '__kwdefaults__'):
+            state['kwdefaults'] = func.__kwdefaults__
         save(state)
         write(pickle.TUPLE)
         write(pickle.REDUCE)  # applies _fill_function on the tuple
@@ -1075,6 +1077,8 @@ def _fill_function(*args):
         func.__module__ = state['module']
     if 'qualname' in state:
         func.__qualname__ = state['qualname']
+    if 'kwdefaults' in state:
+        func.__kwdefaults__ = state['kwdefaults']
 
     cells = func.__closure__
     if cells is not None:

tests/cloudpickle_test.py

@@ -1392,6 +1392,28 @@ def g():
             cloned_func = pickle_depickle(func, protocol=self.protocol)
             assert cloned_func() == "hello from a {}!".format(source)
 
+    @pytest.mark.skipif(sys.version_info[0] < 3,
+                        reason="keyword only arguments were introduced in "
+                               "python 3")
+    def test_interactively_defined_func_with_keyword_only_argument(self):
+        # fixes https://github.com/cloudpipe/cloudpickle/issues/263
+        # The source code of this test is bundled in a string and is ran from
+        # the __main__ module of a subprocess in order to avoid a SyntaxError
+        # in python2 when pytest imports this file, as the keyword-only syntax
+        # is python3-only.
+        code = """
+        from cloudpickle import loads, dumps
+
+        def f(a, *, b=1):
+            return a + b
+
+        depickled_f = loads(dumps(f, protocol={protocol}))
+
+        for func in (f, depickled_f):
+            assert func(2) == 3
+            assert func.__kwdefaults__ == {{'b': 1}}
+        """.format(protocol=self.protocol)
+        assert_run_python_script(textwrap.dedent(code))
 
 class Protocol2CloudPickleTest(CloudPickleTest):