Merge pull request #223 in LCL/wolframclientforpython from bugfix/gvisor-lock to master

* commit 'c1eb832c359ba152310bb1128da292e6f6d58d2c':
  adding warning
  there is no need for context manager
  adding a dummy context manager

Author: crazyeng

wolframclient/serializers/encoder.py

@@ -8,7 +8,6 @@
 import pkg_resources
 
 from wolframclient.serializers.utils import safe_len
-from wolframclient.utils import six
 from wolframclient.utils.api import multiprocessing
 from wolframclient.utils.dispatch import Dispatch
 from wolframclient.utils.functional import composition, is_iterable, iterate, map
@@ -64,18 +63,10 @@ def _update_plugins(self):
                     raise e
             self.plugins_registry = defaultdict(list)
 
-    if not six.JYTHON:
-        # global lock to avoid multiple dispatcher updating in multithreaded programs.
-        _lock = multiprocessing.Lock()
+    # global lock to avoid multiple dispatcher updating in multithreaded programs.
 
-        def update_dispatch(self):
-            with self._lock:
-                self._update_dispatch()
-                self._update_plugins()
-
-    else:
-
-        def update_dispatch(self):
+    def update_dispatch(self):
+        with multiprocessing.Lock():
             self._update_dispatch()
             self._update_plugins()
 

wolframclient/utils/api.py

@@ -138,7 +138,7 @@
     PackedArray="wolframclient.utils.packedarray.PackedArray",
 )
 
-multiprocessing = API(Lock="multiprocessing.Lock")
+multiprocessing = API(Lock="wolframclient.utils.lock.Lock")
 
 PIL = API(Image="PIL.Image.Image", fromarray="PIL.Image.fromarray", open="PIL.Image.open")
 

wolframclient/utils/lock.py

@@ -0,0 +1,24 @@
+from __future__ import absolute_import, print_function, unicode_literals
+
+import warnings
+
+try:
+    import multithreading
+
+    _lock = multithreading.Lock()
+
+    def Lock():
+        return _lock
+
+
+except (ImportError, OSError):
+
+    # JYTHON is raising an ImportError when running "import multithreading"
+    # GVisor is raising an OSError when running "multithreading.Lock()" because the feature is not implemented
+
+    from contextlib import contextmanager
+
+    @contextmanager
+    def Lock():
+        warnings.warn("Lock is not implemented in the current interpreter.", RuntimeWarning)
+        yield