GraphRenderer breaks custom Hover callbacks

Hi, using CustomJS callbacks in the HoverTool appears to be broken with the GraphRenderer. The callback is never executed and TypeError: undefined is not an object (evaluating 'n.data_source.inspected') is printed to the browser’s console. I didn’t see this issue with other renderers.

I’m using bokeh 0.13.0 and networkx 2.1 with Python 3.6.6 (installed by Anaconda) and Jupyter 4.4.0 on macOS 10.13.5 in Safari 11.1.1

Minimal example

from bokeh.io import show, output_notebook
from bokeh.models import Range1d, Plot, CustomJS, Circle, HoverTool
from bokeh.models.graphs import from_networkx
import networkx as nx

output_notebook()

# create the graph renderer
G = nx.Graph()
G.add_weighted_edges_from([(1, 2, 0.125), (1, 3, 0.75), (2, 4, 1.2), (3, 4, 0.375)])
graph = from_networkx(G, nx.layout.circular_layout, scale=1.8, center=(0,0))

# create a circle just to also test another renderer
c = Circle()
c.x = 0
c.y = 0
c.radius = .1

# build plot
plot  = Plot(x_range=Range1d(-3, 3), y_range=Range1d(-3, 3))
plot.renderers.append(graph)
plot.add_glyph(c)

# this just prints an error to the console: 
# "TypeError: undefined is not an object (evaluating 'n.data_source.inspected')"
hover_tool = HoverTool(
    tooltips="index: @index", 
    callback=CustomJS(code='console.log("foo");'), 
    renderers=[plot.renderers[0]]
)

# this prints "foo" and no error to the console, 
# but it also doesn't allow us to interact with the graph
#hover_tool = HoverTool(
#    tooltips="index: @index", 
#    callback=CustomJS(code='console.log("foo");'), 
#    renderers=[plot.renderers[1]]
#)

plot.add_tools(hover_tool)

show(plot)

[bryevdv]

@felixpatzelt Yes, that’s why I suggested we might just decide to remove GraphRenderer instances automatically. Specifically I think Bokeh should:

• silently exclude them from being added on the JS side when no renderers are given
• issue a valuation error if they explicitly added on the Python side

Alternatively to the second bullet, we could potentially refine the type system to prevent GraphRenderer from being added explicitly on the python side at all.

[bryevdv]

@meenurajapandian please provide actual code and relevant version information. It is not valuable for us to speculate about the details of what you are doing.