Don't hide shared "x/y"ticklabels for grids of non-rectilinear axes.

In particular, hiding the "x/y" (i.e. theta/r) ticklabels doesn't make
sense for polar axes, and I'd guess likewise for most projections other
than the default rectilinear.  Try e.g.
`subplots(2, 2, subplot_kw=dict(projection="polar"), sharex=True, sharey=True)`.

Author: anntzer

lib/matplotlib/gridspec.py

@@ -308,12 +308,13 @@ def subplots(self, *, sharex=False, sharey=False, squeeze=True,
                     self[row, col], **subplot_kw)
 
         # turn off redundant tick labeling
-        if sharex in ["col", "all"]:
-            for ax in axarr.flat:
-                ax._label_outer_xaxis()
-        if sharey in ["row", "all"]:
-            for ax in axarr.flat:
-                ax._label_outer_yaxis()
+        if all(ax.name == "rectilinear" for ax in axarr.flat):
+            if sharex in ["col", "all"]:
+                for ax in axarr.flat:
+                    ax._label_outer_xaxis()
+            if sharey in ["row", "all"]:
+                for ax in axarr.flat:
+                    ax._label_outer_yaxis()
 
         if squeeze:
             # Discarding unneeded dimensions that equal 1.  If we only have one

lib/matplotlib/tests/test_polar.py

@@ -394,3 +394,10 @@ def test_remove_shared_polar(fig_ref, fig_test):
         2, 2, sharey=True, subplot_kw={"projection": "polar"})
     for i in [0, 1, 3]:
         axs.flat[i].remove()
+
+
+def test_shared_polar_keeps_ticklabels():
+    _, axs = plt.subplots(
+        2, 2, subplot_kw=dict(projection="polar"), sharex=True, sharey=True)
+    assert axs[0, 1].xaxis._major_tick_kw["label1On"]
+    assert axs[0, 1].yaxis._major_tick_kw["label1On"]