Add sharing guard.

lkjell · lkjell · commit 10efd2bd6ff7 · 2018-03-09T19:29:23.000+01:00
diff --git a/lib/matplotlib/axes/_base.py b/lib/matplotlib/axes/_base.py
@@ -4338,12 +4338,16 @@ def unshare_axes(self, axes=None):
     @staticmethod
     def _share_axes_symmetric(A, B, shared_axes):
         """Share A -> B, and B -> A"""
+        if A is B:
+            return
         _AxesBase._share_axes_asymmetric(A, B, shared_axes)
         _AxesBase._share_axes_asymmetric(B, A, shared_axes)
 
     @staticmethod
     def _share_axes_asymmetric(A, B, shared_axes):
         """Share A -> B"""
+        if A is B:
+            return
         getattr(A, "_shared_{}_axes".format(shared_axes)).add(B)
         getattr(B, "_shared_{}_inv_axes".format(shared_axes)).add(A)
 
diff --git a/lib/matplotlib/tests/test_axes.py b/lib/matplotlib/tests/test_axes.py
@@ -5918,5 +5918,4 @@ def test_share_unshare_3d_axes():
     assert ax1 in sharedz
 
     sharedz = ax1._shared_z_axes
-    assert ax2 in sharedz
-    
+    assert ax2 in sharedz
