BUG : fix cla behavior with twinx

Closes matplotlib#3633

Added more special-case logic for twined axes.

Author: tacaswell

lib/matplotlib/axes/_base.py

@@ -816,6 +816,16 @@ def _gen_axes_spines(self, locations=None, offset=0.0, units='inches'):
     def cla(self):
         """Clear the current axes."""
         # Note: this is called by Axes.__init__()
+
+        # stash the current visibility state
+        if hasattr(self, 'patch'):
+            patch_visible = self.patch.get_visible()
+        else:
+            patch_visible = True
+
+        xaxis_visible = self.xaxis.get_visible()
+        yaxis_visible = self.yaxis.get_visible()
+
         self.xaxis.cla()
         self.yaxis.cla()
         for name, spine in six.iteritems(self.spines):
@@ -941,6 +951,13 @@ def cla(self):
 
         self._shared_x_axes.clean()
         self._shared_y_axes.clean()
+        if self._sharex:
+            self.xaxis.set_visible(xaxis_visible)
+            self.patch.set_visible(patch_visible)
+
+        if self._sharey:
+            self.yaxis.set_visible(yaxis_visible)
+            self.patch.set_visible(patch_visible)
 
     def clear(self):
         """clear the axes"""

lib/matplotlib/tests/test_axes.py

@@ -4,7 +4,7 @@
 import six
 from six.moves import xrange
 
-from nose.tools import assert_equal, assert_raises
+from nose.tools import assert_equal, assert_raises, assert_false, assert_true
 import datetime
 
 import numpy as np
@@ -100,6 +100,30 @@ def test_twin_axis_locaters_formatters():
     ax3 = ax1.twinx()
 
 
+@cleanup
+def test_twinx_cla():
+    fig, ax = plt.subplots()
+    ax2 = ax.twinx()
+    ax3 = ax2.twiny()
+    plt.draw()
+    assert_false(ax2.xaxis.get_visible())
+    assert_false(ax2.patch.get_visible())
+    ax2.cla()
+    ax3.cla()
+
+    assert_false(ax2.xaxis.get_visible())
+    assert_false(ax2.patch.get_visible())
+    assert_true(ax2.yaxis.get_visible())
+
+    assert_true(ax3.xaxis.get_visible())
+    assert_false(ax3.patch.get_visible())
+    assert_false(ax3.yaxis.get_visible())
+
+    assert_true(ax.xaxis.get_visible())
+    assert_true(ax.patch.get_visible())
+    assert_true(ax.yaxis.get_visible())
+
+
 @image_comparison(baseline_images=["autoscale_tiny_range"], remove_text=True)
 def test_autoscale_tiny_range():
     # github pull #904