Merge pull request matplotlib#7504 from efiring/patch_facecolor_none

BUG: preserve 'none' facecolor in Patch. 

Closes matplotlib#7478.

Author: tacaswell

lib/matplotlib/patches.py

@@ -356,7 +356,7 @@ def set_alpha(self, alpha):
             except TypeError:
                 raise TypeError('alpha must be a float or None')
         artist.Artist.set_alpha(self, alpha)
-        self._set_facecolor(self._facecolor)
+        self._set_facecolor(self._original_facecolor)
         self._set_edgecolor(self._original_edgecolor)
         # stale is already True
 

lib/matplotlib/tests/test_patches.py

@@ -173,6 +173,14 @@ def test_patch_alpha_override():
     ax.set_ylim([-1, 2])
 
 
+@cleanup(style='default')
+def test_patch_color_none():
+    # Make sure the alpha kwarg does not override 'none' facecolor.
+    # Addresses issue #7478.
+    c = plt.Circle((0, 0), 1, facecolor='none', alpha=1)
+    assert c.get_facecolor()[0] == 0
+
+
 @image_comparison(baseline_images=['patch_custom_linestyle'],
                   remove_text=True)
 def test_patch_custom_linestyle():