Add __getstate__ / __setstate__ method to dim to fix RecursionError (#…

…4582)

holoviews/tests/util/testtransform.py

@@ -5,6 +5,7 @@
 from __future__ import division
 
 import sys
+import pickle
 
 from collections import OrderedDict
 from unittest import skipIf
@@ -481,7 +482,7 @@ def test_xarray_quantile_method(self):
     def test_xarray_roll_method(self):
         expr = dim('z').xr.roll({'x': 1}, roll_coords=False)
         self.assert_apply_xarray(expr, self.dataset_xarray.data.z.roll({'x': 1}, roll_coords=False))
-        
+
     @xr_skip
     @py2_skip
     def test_xarray_coarsen_method(self):
@@ -513,3 +514,8 @@ def test_dynamic_kwarg(self):
         self.assert_apply(expr, np.round(self.linear_floats, 1))
         p.a = 2
         self.assert_apply(expr, np.round(self.linear_floats, 2))
+
+    def test_pickle(self):
+        expr = (((dim('float')-2)*3)**2)
+        expr2 = pickle.loads(pickle.dumps(expr))
+        self.assertEqual(expr, expr2)

holoviews/util/transform.py

@@ -242,6 +242,12 @@ def __init__(self, obj, *args, **kwargs):
                           'reverse': kwargs.pop('reverse', False)}]
         self.ops = ops
 
+    def __getstate__(self):
+        return self.__dict__
+
+    def __setstate__(self, state):
+        self.__dict__.update(state)
+
     @property
     def _current_accessor(self):
         if self.ops and self.ops[-1]['kwargs'].get('accessor'):