matplotlib · timhoffm · Apr 29, 2021 · Apr 17, 2021
diff --git a/lib/matplotlib/axis.py b/lib/matplotlib/axis.py
@@ -552,6 +552,8 @@ class Ticker:
     def __init__(self):
         self._locator = None
         self._formatter = None
+        self._locator_is_default = True
+        self._formatter_is_default = True
 
     @property
     def locator(self):
@@ -689,6 +691,38 @@ def __init__(self, axes, pickradius=15):
         self.clear()
         self._set_scale('linear')
 
+    @property
+    def isDefault_majloc(self):
+        return self.major._locator_is_default
+
+    @isDefault_majloc.setter
+    def isDefault_majloc(self, value):
+        self.major._locator_is_default = value
+
+    @property
+    def isDefault_majfmt(self):
+        return self.major._formatter_is_default
+
+    @isDefault_majfmt.setter
+    def isDefault_majfmt(self, value):
+        self.major._formatter_is_default = value
+
+    @property
+    def isDefault_minloc(self):
+        return self.minor._locator_is_default
+
+    @isDefault_minloc.setter
+    def isDefault_minloc(self, value):
+        self.minor._locator_is_default = value
+
+    @property
+    def isDefault_minfmt(self):
+        return self.minor._formatter_is_default
+
+    @isDefault_minfmt.setter
+    def isDefault_minfmt(self, value):
+        self.minor._formatter_is_default = value
+
     # During initialization, Axis objects often create ticks that are later
     # unused; this turns out to be a very slow step.  Instead, use a custom
     # descriptor to make the tick lists lazy and instantiate them as needed.

diff --git a/lib/matplotlib/figure.py b/lib/matplotlib/figure.py
@@ -916,33 +916,10 @@ def _reset_locators_and_formatters(axis):
             # Set the formatters and locators to be associated with axis
             # (where previously they may have been associated with another
             # Axis instance)
-            #
-            # Because set_major_formatter() etc. force isDefault_* to be False,
-            # we have to manually check if the original formatter was a
-            # default and manually set isDefault_* if that was the case.
-            majfmt = axis.get_major_formatter()
-            isDefault = majfmt.axis.isDefault_majfmt
-            axis.set_major_formatter(majfmt)
-            if isDefault:
-                majfmt.axis.isDefault_majfmt = True
-
-            majloc = axis.get_major_locator()
-            isDefault = majloc.axis.isDefault_majloc
-            axis.set_major_locator(majloc)
-            if isDefault:
-                majloc.axis.isDefault_majloc = True
-
-            minfmt = axis.get_minor_formatter()
-            isDefault = majloc.axis.isDefault_minfmt
-            axis.set_minor_formatter(minfmt)
-            if isDefault:
-                minfmt.axis.isDefault_minfmt = True
-
-            minloc = axis.get_minor_locator()
-            isDefault = majloc.axis.isDefault_minloc
-            axis.set_minor_locator(minloc)
-            if isDefault:
-                minloc.axis.isDefault_minloc = True
+            axis.get_major_formatter().set_axis(axis)
+            axis.get_major_locator().set_axis(axis)
+            axis.get_minor_formatter().set_axis(axis)
+            axis.get_minor_locator().set_axis(axis)
 
         def _break_share_link(ax, grouper):
             siblings = grouper.get_siblings(ax)

diff --git a/lib/matplotlib/projections/polar.py b/lib/matplotlib/projections/polar.py
@@ -425,6 +425,9 @@ def __init__(self, base, axes=None):
         self.base = base
         self._axes = axes
 
+    def set_axis(self, axis):
+        self.base.set_axis(axis)
+
     def __call__(self):
         # Ensure previous behaviour with full circle non-annular views.
         if self._axes:

diff --git a/lib/matplotlib/tests/test_polar.py b/lib/matplotlib/tests/test_polar.py
@@ -379,3 +379,18 @@ def test_axvspan():
     ax = plt.subplot(projection="polar")
     span = plt.axvspan(0, np.pi/4)
     assert span.get_path()._interpolation_steps > 1
+
+
+@check_figures_equal(extensions=["png"])
+def test_remove_shared_polar(fig_ref, fig_test):
+    # Removing shared polar axes used to crash.  Test removing them, keeping in
+    # both cases just the lower left axes of a grid to avoid running into a
+    # separate issue (now being fixed) of ticklabel visibility for shared axes.
+    axs = fig_ref.subplots(
+        2, 2, sharex=True, subplot_kw={"projection": "polar"})
+    for i in [0, 1, 3]:
+        axs.flat[i].remove()
+    axs = fig_test.subplots(
+        2, 2, sharey=True, subplot_kw={"projection": "polar"})
+    for i in [0, 1, 3]:
+        axs.flat[i].remove()