Avoid matplotlib warning about edgecolor on an unfilled scatterplot m…

…arker (#2636)

(cherry picked from commit c20d910)

seaborn/relational.py

@@ -632,7 +632,6 @@ def plot(self, ax, kws):
 
         # Set defaults for other visual attributes
         kws.setdefault("linewidth", .08 * np.sqrt(np.percentile(s, 10)))
-        kws.setdefault("edgecolor", "w")
 
         if "style" in self.variables:
             # Use a representative marker so scatter sets the edgecolor
@@ -642,6 +641,14 @@ def plot(self, ax, kws):
             example_marker = self._style_map(example_level, "marker")
             kws.setdefault("marker", example_marker)
 
+        # Conditionally set the marker edgecolor based on whether the marker is "filled"
+        # See https://github.com/matplotlib/matplotlib/issues/17849 for context
+        m = kws.get("marker", mpl.rcParams.get("marker", "o"))
+        if not isinstance(m, mpl.markers.MarkerStyle):
+            m = mpl.markers.MarkerStyle(m)
+        if m.is_filled():
+            kws.setdefault("edgecolor", "w")
+
         # TODO this makes it impossible to vary alpha with hue which might
         # otherwise be useful? Should we just pass None?
         kws["alpha"] = 1 if self.alpha == "auto" else self.alpha

seaborn/tests/test_relational.py

@@ -1755,6 +1755,12 @@ def test_datetime_scale(self, long_df):
         # https://github.com/matplotlib/matplotlib/issues/17586
         ax.get_xlim()[0] > ax.xaxis.convert_units(np.datetime64("2002-01-01"))
 
+    def test_unfilled_marker_edgecolor_warning(self, long_df):  # GH2636
+
+        with pytest.warns(None) as record:
+            scatterplot(data=long_df, x="x", y="y", marker="+")
+        assert not record
+
     def test_scatterplot_vs_relplot(self, long_df, long_semantics):
 
         ax = scatterplot(data=long_df, **long_semantics)