Add Operation._propagate_dataset class flag to control whether to aut…

…omatically

propagate dataset through operation

holoviews/core/operation.py

@@ -70,6 +70,10 @@ class Operation(param.ParameterizedFunction):
     _postprocess_hooks = []
     _allow_extra_keywords=False
 
+    # Flag indicating whether to automatically propagate the .dataset property from
+    # the input of the operation to the result
+    _propagate_dataset = True
+
     @classmethod
     def search(cls, element, pattern):
         """
@@ -126,7 +130,8 @@ def _apply(self, element, key=None):
         for hook in self._postprocess_hooks:
             ret = hook(self, ret, **kwargs)
 
-        if isinstance(ret, Dataset) and isinstance(element, Dataset):
+        if (self._propagate_dataset and
+                isinstance(ret, Dataset) and isinstance(element, Dataset)):
             ret._dataset = element.dataset.clone()
             ret._pipeline = element_pipeline.instance(
                 operations=element_pipeline.operations + [

holoviews/tests/core/testdatasetproperty.py

@@ -11,7 +11,7 @@
 from holoviews import Dataset, Curve, Dimension, Scatter, Distribution
 from holoviews.core import Apply, Redim
 from holoviews.element.comparison import ComparisonTestCase
-from holoviews.operation import histogram
+from holoviews.operation import histogram, function
 
 try:
     from holoviews.operation.datashader import dynspread, datashade, rasterize
@@ -826,3 +826,21 @@ def test_redim_curve(self):
         self.assertEqual(
             curve.pipeline(self.ds2), curve2
         )
+
+
+class OperationTestCase(DatasetPropertyTestCase):
+    def test_propagate_dataset(self):
+        op = function.instance(
+            fn=lambda ds: ds.iloc[:5].clone(dataset=None, pipeline=None)
+        )
+        new_ds = op(self.ds)
+        self.assertEqual(new_ds.dataset, self.ds)
+
+    def test_do_not_propagate_dataset(self):
+        op = function.instance(
+            fn=lambda ds: ds.iloc[:5].clone(dataset=None, pipeline=None)
+        )
+        # Disable dataset propagation
+        op._propagate_dataset = False
+        new_ds = op(self.ds)
+        self.assertEqual(new_ds.dataset, new_ds)