Bug report

Bug summary

With matplotlib=2.1.2, when I add an Arc patch to an Axes instance via a PatchCollection, the arc always appear as a complete ellipse, regardless of values I set for theta1 and theta2. When I add the Arc directly via Axes.add_patch, I don't have this problem.

Last time I checked (matplotlib 1.4.0), this wasn't an issue. I haven't bisected to figure out when the problem started.

Code for reproduction

import matplotlib.patches as mpatches
import matplotlib.pyplot as plt
import matplotlib.collections as mcol
arc = mpatches.Arc([.5,.5], .5, 1, theta1=0, theta2=60, angle=20)
col = mcol.PatchCollection(patches=[arc])
col_style = mcol.PatchCollection(patches=[arc], facecolors='none', edgecolors='k')

fig, (ax1,ax2,ax3) = plt.subplots(1,3, figsize=(15,4))
ax1.set_title('add_patch')
ax1.add_patch(arc)
ax2.set_title('add_collection')
ax2.add_collection(col)
ax3.set_title('add_collection, style')
ax3.add_collection(col_style)
plt.show()

Actual outcome

Expected outcome

The arc in all three figures should be a 60deg arc, not a complete ellipse.

Matplotlib version

• Operating system: CentOS 7
• Matplotlib version: 2.1.2
• Matplotlib backend (print(matplotlib.get_backend())): module://ipykernel.pylab.backend_inline
• Python version: 2.7.14 |Anaconda, Inc.| (default, Dec 7 2017, 17:05:42) [GCC 7.2.0]
• Jupyter version (if applicable): 4.4.0

I installed matplotlib via conda: conda create -n py2 python=2 anaconda