Hover tooltip breaks with zero-width wedges

[PavloFesenko]

For defects or deficiencies, please provide ALL OF THE FOLLOWING:

ALL software version info (bokeh, python, notebook, OS, browser, any other relevant packages)

bokeh 1.0.4, python 3.6.6, notebook Kaggle, OS Windows 10, browser Chrome

Description of expected behavior and the observed behavior

When one of the values in the wedge/pie chart is 0, the hover tooltip shows the column instead of the single value.

Complete, minimal, self-contained example code that reproduces the issue

from math import pi

import pandas as pd

from bokeh.io import output_file, show
from bokeh.palettes import Category20c
from bokeh.plotting import figure
from bokeh.transform import cumsum

output_file("pie.html")

x = {
    'United States': 0,
    'United Kingdom': 93,
    'Japan': 89,
    'China': 63,
    'Germany': 44,
    'India': 42,
    'Italy': 40,
    'Australia': 35,
    'Brazil': 32,
    'France': 31,
    'Taiwan': 31,
    'Spain': 29
}

data = pd.Series(x).reset_index(name='value').rename(columns={'index':'country'})
data['angle'] = data['value']/data['value'].sum() * 2*pi
data['color'] = Category20c[len(x)]

p = figure(plot_height=350, title="Pie Chart", toolbar_location=None,
           tools="hover", tooltips="@country: @value", x_range=(-0.5, 1.0))

p.wedge(x=0, y=1, radius=0.4,
        start_angle=cumsum('angle', include_zero=True), end_angle=cumsum('angle'),
        line_color="white", fill_color='color', legend='country', source=data)

p.axis.axis_label=None
p.axis.visible=False
p.grid.grid_line_color = None

show(p)

Screenshots or screencasts of the bug in action

[bryevdv]

Thanks for the detailed report @PavloFesenko and especially the complete test case

[bryevdv]

Offhand guess: when the angle is zero it ends up hit-testing the entire circle

[PavloFesenko]

@bryevdv , thanks for a quick response! One can overcome this bug by replacing 0 with a small value, for example, 0.001 but this is just a temporary fix.