In scatter, fix single rgb edgecolors handling

efiring · efiring · commit c6c7c750aed8 · 2021-02-18T13:08:06.000-10:00
Closes #19066.
diff --git a/lib/matplotlib/axes/_axes.py b/lib/matplotlib/axes/_axes.py
@@ -4507,6 +4507,11 @@ def scatter(self, x, y, s=None, c=None, marker=None, cmap=None, norm=None,
             x, y, s, c, colors, edgecolors, linewidths = \
                 cbook._combine_masks(
                     x, y, s, c, colors, edgecolors, linewidths)
+        # Unmask edgecolors if it was actually a single RGB or RGBA.
+        if (x.size in (3, 4)
+                and np.ma.is_masked(edgecolors)
+                and not np.ma.is_masked(orig_edgecolor)):
+            edgecolors = edgecolors.data
 
         scales = s   # Renamed for readability below.
 
diff --git a/lib/matplotlib/tests/test_axes.py b/lib/matplotlib/tests/test_axes.py
@@ -2172,6 +2172,15 @@ def test_scatter_size_arg_size(self):
         with pytest.raises(ValueError, match='float array-like'):
             plt.scatter(x, x, 'foo')
 
+    def test_scatter_edgecolor_RGB(self):
+        # Github issue 19066
+        coll = plt.scatter([1, 2, 3], [1, np.nan, np.nan],
+                            edgecolor=(1, 0, 0))
+        assert mcolors.same_color(coll.get_edgecolor(), (1, 0, 0))
+        coll = plt.scatter([1, 2, 3, 4], [1, np.nan, np.nan, 1],
+                            edgecolor=(1, 0, 0, 1))
+        assert mcolors.same_color(coll.get_edgecolor(), (1, 0, 0, 1))
+
     @check_figures_equal(extensions=["png"])
     def test_scatter_invalid_color(self, fig_test, fig_ref):
         ax = fig_test.subplots()
