bugfix for PathSimplifier

[r3kste]

PR summary

Issue number: 17914
PathSimplifier should ignore vertices corresponding Path.CLOSEPOLY, and rather replace them with the most recent Path.MOVETO vertex.

Code for reproducing the bug

import numpy as np
import matplotlib.pyplot as plt
from matplotlib.path import Path
from matplotlib.patches import PathPatch

p = Path(
    [(0, 0), (1, 0), (1, 1), (np.nan, np.nan)],
    [Path.MOVETO, Path.LINETO, Path.LINETO, Path.CLOSEPOLY],
)

# Remove this to see expected output
p = p.cleaned(simplify=True)

fig, ax = plt.subplots()
patch = PathPatch(p, facecolor="none", edgecolor="blue")
ax.add_patch(patch)
ax.set_xlim(-1, 2)
ax.set_ylim(-1, 2)

plt.show()

Expected Outcome

Actual Outcome

PR checklist

• "closes #0000" is in the body of the PR description to link the related issue
• new and changed code is tested
• Plotting related features are demonstrated in an example
• New Features and API Changes are noted with a directive and release note
• Documentation complies with general and docstring guidelines

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