Fixed resolving Selection1D in bokeh callback

holoviews/plotting/bokeh/callbacks.py

@@ -1,7 +1,7 @@
 from collections import defaultdict
 
 import param
-from bokeh.models import (CustomJS, FactorRange, DatetimeAxis, ColumnDataSource)
+from bokeh.models import (CustomJS, FactorRange, DatetimeAxis, ColumnDataSource, Selection)
 
 from ...core import OrderedDict
 from ...streams import (Stream, PointerXY, RangeXY, Selection1D, RangeX,
@@ -355,6 +355,9 @@ def resolve_attr_spec(cls, spec, cb_obj, model=None):
                 continue
             if isinstance(resolved, dict):
                 resolved = resolved.get(p)
+            elif isinstance(resolved, Selection) and p in ['1d', 'indices']:
+                # Handle resolving bokeh Selection 1d indices
+                resolved = resolved[p]
             else:
                 resolved = getattr(resolved, p, None)
         return {'id': model.ref['id'], 'value': resolved}

tests/testbokehcallbacks.py

@@ -12,7 +12,7 @@
     from holoviews.plotting.bokeh.util import bokeh_version
 
     from bokeh.events import Tap
-    from bokeh.models import Range1d, Plot
+    from bokeh.models import Range1d, Plot, ColumnDataSource, Selection
     bokeh_renderer = Store.renderers['bokeh']
 except:
     bokeh_renderer = None
@@ -81,6 +81,12 @@ def test_server_callback_resolve_attr_spec_range1d_end(self):
         msg = Callback.resolve_attr_spec('x_range.attributes.end', range1d)
         self.assertEqual(msg, {'id': range1d.ref['id'], 'value': 10})
 
+    def test_server_callback_resolve_attr_spec_source_selected(self):
+        source = ColumnDataSource()
+        source.selected = Selection(indices=[1, 2, 3])
+        msg = Callback.resolve_attr_spec('cb_obj.selected.1d.indices', source)
+        self.assertEqual(msg, {'id': source.ref['id'], 'value': [1, 2, 3]})
+
     def test_server_callback_resolve_attr_spec_tap_event(self):
         plot = Plot()
         event = Tap(plot, x=42)