Fix overlay of two-level categorical plots and HLine (#5203)

holoviews/plotting/bokeh/element.py

@@ -2,6 +2,8 @@
 
 import sys
 import warnings
+
+from itertools import chain
 from types import FunctionType
 
 import param
@@ -2317,13 +2319,13 @@ def _get_factors(self, overlay, ranges):
             if el is not None:
                 elranges = util.match_spec(el, ranges)
                 xfs, yfs = sp._get_factors(el, elranges)
-                xfactors.append(xfs)
-                yfactors.append(yfs)
-        if xfactors:
-            xfactors = np.concatenate(xfactors)
-        if yfactors:
-            yfactors = np.concatenate(yfactors)
-        return util.unique_array(xfactors), util.unique_array(yfactors)
+                if len(xfs):
+                    xfactors.append(xfs)
+                if len(yfs):
+                    yfactors.append(yfs)
+        xfactors = list(util.unique_iterator(chain(*xfactors)))
+        yfactors = list(util.unique_iterator(chain(*yfactors)))
+        return xfactors, yfactors
 
 
     def _get_axis_dims(self, element):

holoviews/tests/plotting/bokeh/testoverlayplot.py

@@ -3,15 +3,15 @@
 
 from holoviews.core import NdOverlay, HoloMap, DynamicMap, Overlay
 from holoviews.core.options import Cycle
-from holoviews.element import Curve, Points, ErrorBars, Scatter, Text, VLine
+from holoviews.element import Bars, Curve, ErrorBars, HLine, Points, Scatter, Text, VLine
 from holoviews.streams import Stream, Tap
 from holoviews.util import Dynamic
 
 from ...utils import LoggingComparisonTestCase
 from .testplot import TestBokehPlot, bokeh_renderer
 
 try:
-    from bokeh.models import FixedTicker, HoverTool, FactorRange, Range1d
+    from bokeh.models import FixedTicker, HoverTool, FactorRange, Span, Range1d
 except:
     pass
 
@@ -192,6 +192,16 @@ def test_points_errorbars_text_ndoverlay_categorical_xaxis(self):
         for xs, factor in zip(error_plot.handles['source'].data['base'], factors):
             self.assertEqual(factor, xs)
 
+    def test_overlay_categorical_two_level(self):
+        bars = Bars([('A', 'a', 1), ('B', 'b', 2), ('A', 'b', 3), ('B', 'a', 4)],
+                    kdims=['Upper', 'Lower'])
+
+        plot = bokeh_renderer.get_plot(bars * HLine(2))
+        x_range = plot.handles['x_range']
+        assert isinstance(x_range, FactorRange)
+        assert x_range.factors == [('A', 'a'), ('A', 'b'), ('B', 'a'), ('B', 'b')]
+        assert isinstance(plot.state.renderers[-1], Span)
+
     def test_points_errorbars_text_ndoverlay_categorical_xaxis_invert_axes(self):
         overlay = NdOverlay({i: Points(([chr(65+i)]*10,np.random.randn(10)))
                              for i in range(5)})