test_polar_alignment fails. The tick 0.0 is now missing but I don't understand how the change is affecting it.

If you stick a print(fig.axes[0].yaxis.get_major_locator()) at the end of that test, before this PR it gives a FixedLocator, but after it gives a RadialLocator. Makes sense, but I guess that might be the root cause of the failing image test.

diff --git a/lib/matplotlib/projections/polar.py b/lib/matplotlib/projections/polar.py
index f20498b271..40f431aefb 100644
--- a/lib/matplotlib/projections/polar.py
+++ b/lib/matplotlib/projections/polar.py
@@ -444,7 +444,7 @@ class RadialLocator(mticker.Locator):
             if _is_full_circle_rad(*self._axes.viewLim.intervalx):
                 rorigin = self._axes.get_rorigin() * self._axes.get_rsign()
                 if self._axes.get_rmin() <= rorigin:
-                    return [tick for tick in self.base() if tick > rorigin]
+                    return [tick for tick in self.base() if tick >= rorigin]
         return self.base()
 
     def _zero_in_bounds(self):

☝️ fixes the test that's broken - seems like a sensible change to make, but I'm not sure if it breaks any other tests.

Thanks for figuring out. Actually, there is no tick at the center in all the polar examples.

From a quick look, I don’t fully understand the code you pointed to, but given this is under the is_full_circle_rad condition, it might be intentional to leave out the tick at the center. Will need to have a closer look at context conditions and history of that code.

cross check: MATLAB does not do this. So it’s at least not something built in to match their behavior.

I've simply updated the refrence image. As said above, other radial plots don't have the center 0 either. Therefore I claim the reference image was wrong. If we wanted to add the 0 back in, that'd need to be a systematic appoach.

Owee, I'm MrMeeseeks, Look at me.

There seem to be a conflict, please backport manually. Here are approximate instructions:

1. Checkout backport branch and update it.

git checkout v3.10.x
git pull

2. Cherry pick the first parent branch of the this PR on top of the older branch:

git cherry-pick -x -m1 1663e9af1b63409f1a98b8ff6bc0c5c07b47054c

3. You will likely have some merge/cherry-pick conflict here, fix them and commit:

git commit -am 'Backport PR #30174: FIX: Ensure Locators on RadialAxis are always correctly wrapped'

4. Push to a named branch:

git push YOURFORK v3.10.x:auto-backport-of-pr-30174-on-v3.10.x

5. Create a PR against branch v3.10.x, I would have named this PR:

"Backport PR #30174 on branch v3.10.x (FIX: Ensure Locators on RadialAxis are always correctly wrapped)"

And apply the correct labels and milestones.

Congratulations — you did some good work! Hopefully your backport PR will be tested by the continuous integration and merged soon!

Remember to remove the Still Needs Manual Backport label once the PR gets merged.

If these instructions are inaccurate, feel free to suggest an improvement.

Not worth a manual backport. - I anticipate that 3.11 will be released in the not too far future, and a possible 3.10.4 will not be much earlier than that.