Add tests

Author: philippjfr

holoviews/plotting/util.py

@@ -1369,6 +1369,8 @@ def _process(self, element, key=None):
             except TypeError:
                 # Issue #5619, cudf.core.index.StringIndex is not iterable.
                 cats = list(hvds.data.dtypes[column].categories.to_pandas())
+            except AttributeError:
+                cats = list(unique_iterator(hvds.data[column]))
             if cats == ['__UNKNOWN_CATEGORIES__']:
                 cats = list(hvds.data[column].cat.as_known().categories)
         else:
@@ -1379,7 +1381,10 @@ def _process(self, element, key=None):
         else:
             shade_op = element.pipeline.find(shade, skip_nonlinked=False)
         if shade_op is None:
-            colors = process_cmap(self.p.cmap, ncolors=len(cats), categorical=True)
+            if self.p.cmap is None:
+                colors = ds.colors.Sets1to3
+            else:
+                colors = process_cmap(self.p.cmap, ncolors=len(cats), categorical=True)
         else:
             colors = shade_op.color_key or ds.colors.Sets1to3
         color_data = [(0, 0, cat) for cat in cats]

holoviews/tests/plotting/bokeh/test_rasterplot.py

@@ -5,7 +5,7 @@
 import pytest
 from bokeh.models import CustomJSHover, HoverTool
 
-from holoviews.element import RGB, Image, ImageStack, Raster
+from holoviews.element import RGB, Image, ImageStack, Points, Raster
 from holoviews.plotting.bokeh.raster import ImageStackPlot
 from holoviews.plotting.bokeh.util import BOKEH_GE_3_4_0
 
@@ -473,3 +473,36 @@ def setUp(self):
         self.ysize = 3
         self.xsize = 4
         super().setUp()
+
+
+class TestSyntheticLegendPlot(TestBokehPlot):
+    __test__ = True
+
+    def setUp(self):
+        try:
+            import datashader as ds
+
+            from holoviews.operation.datashader import datashade, rasterize
+        except Exception as e:
+            print(e)
+            raise SkipTest('Datashader not available')
+        points = Points([(0, 0, 'A'), (1, 1, 'B'), (2, 2, 'C')], vdims=['Label'])
+        kwargs = dict(aggregator=ds.by('Label'), dynamic=False, width=10, height=10)
+        self.img_stack = rasterize(points, **kwargs).opts(show_legend=True)
+        self.rgb = datashade(points, **kwargs).opts(show_legend=True)
+
+    def test_image_stack_legend(self):
+        plot = bokeh_renderer.get_plot(self.img_stack)
+        mapper = plot.handles['synthetic_color_mapper']
+        assert mapper.factors == ['A', 'B', 'C']
+        glyph = plot._legend_plot.handles['glyph']
+        assert glyph.fill_color.field == 'color'
+        assert glyph.fill_color.transform is mapper
+
+    def test_rgb_legend(self):
+        plot = bokeh_renderer.get_plot(self.rgb)
+        mapper = plot.handles['synthetic_color_mapper']
+        assert mapper.factors == ['A', 'B', 'C']
+        glyph = plot._legend_plot.handles['glyph']
+        assert glyph.fill_color.field == 'color'
+        assert glyph.fill_color.transform is mapper