Upstream CI failures

[kafitzgerald]

We have several failures right now in Upstream CI. It's looks like they're coming from Matplotlib updates.

In particular the following examples are impacted:

• NCL_xy_16.py
• NCL_overlay_11b.py
• NCL_hov_3.py
• NCL_coneff_11.py

Log

Unexpected failing examples (4):

../Gallery/XY/NCL_xy_16.py failed leaving traceback:

Traceback (most recent call last):
  File "/home/runner/work/geocat-examples/geocat-examples/Gallery/XY/NCL_xy_16.py", line 102, in <module>
    plt.legend(handles,
  File "/home/runner/micromamba/envs/geocat-examples/lib/python3.11/site-packages/matplotlib/pyplot.py", line 3593, in legend
    return gca().legend(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/runner/micromamba/envs/geocat-examples/lib/python3.11/site-packages/matplotlib/axes/_axes.py", line 335, in legend
    self.legend_ = mlegend.Legend(self, handles, labels, **kwargs)
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/runner/micromamba/envs/geocat-examples/lib/python3.11/site-packages/matplotlib/legend.py", line 462, in __init__
    if len(handles) < 2:
       ^^^^^^^^^^^^
TypeError: object of type 'list_reverseiterator' has no len()

../Gallery/Overlays/NCL_overlay_11b.py failed leaving traceback:

Traceback (most recent call last):
  File "/home/runner/work/geocat-examples/geocat-examples/Gallery/Overlays/NCL_overlay_11b.py", line 185, in <module>
    for col in cf.collections:
               ^^^^^^^^^^^^^^
AttributeError: 'GeoContourSet' object has no attribute 'collections'

../Gallery/Contours/NCL_hov_3.py failed leaving traceback:

Traceback (most recent call last):
  File "/home/runner/work/geocat-examples/geocat-examples/Gallery/Contours/NCL_hov_3.py", line 52, in <module>
    for i, collection in enumerate(cf.collections):
                                   ^^^^^^^^^^^^^^
AttributeError: 'QuadContourSet' object has no attribute 'collections'

../Gallery/Contours/NCL_coneff_11.py failed leaving traceback:

Traceback (most recent call last):
  File "/home/runner/work/geocat-examples/geocat-examples/Gallery/Contours/NCL_coneff_11.py", line 62, in <module>
    for i, collection in enumerate(p.collections):
                                   ^^^^^^^^^^^^^
AttributeError: 'QuadContourSet' object has no attribute 'collections'

---

[kafitzgerald]

I suspect it's because of these changes:

• ContourSet moving to a single Collection - https://matplotlib.org/devdocs/api/next_api_changes/removals/28767-REC.html
• Some changes related to legend internals that mean our current workaround doesn't work anymore (thankfully there's now a better option)

[kafitzgerald]

This is blocked while we wait for the Matplotlib fix for different colored hatching to be backported to v3.9.x or until we do something like leverage packaging to check Matplotlib versions for us so we can support a broader range of Matplotlib versions. I'm starting to think we should just do this. I'll open a new issue to discuss / outline my thoughts.

[kafitzgerald]

It looks like like I missed the usage of collections in NCL_hov_3.py here:

geocat-examples/Gallery/Contours/NCL_hov_3.py

Line 77 in 1431c48

cs.collections[3].set_linewidth(1)

That can get fixed along with the hatching and linewidth items below after the Matplotlib 3.9.3 release

geocat-examples/Gallery/Contours/NCL_coneff_11.py

Lines 62 to 64 in 1431c48

	for i, collection in enumerate(p.collections):
	collection.set_edgecolor(colors[i % len(colors)])
	collection.set_linewidth(0.)

[kafitzgerald]

Looks like the matplotlib 3.9.3 release is out 🎉 so we should be able to more easily / robustly fix the rest of this.