Always use unit width for categorical axes (#3390)

Author: mwaskom

seaborn/categorical.py

@@ -375,6 +375,11 @@ def _configure_legend(self, ax, func, common_kws=None, semantic_kws=None):
     @property
     def _native_width(self):
         """Return unit of width separating categories on native numeric scale."""
+        # Categorical data always have a unit width
+        if self.var_types[self.orient] == "categorical":
+            return 1
+
+        # Otherwise, define the width as the smallest space between observations
         unique_values = np.unique(self.comp_data[self.orient])
         if len(unique_values) > 1:
             native_width = np.nanmin(np.diff(unique_values))

tests/test_categorical.py

@@ -2198,9 +2198,16 @@ def test_width_native_scale(self):
         width = .5
         x, y = [4, 6, 10], [1, 2, 3]
         ax = barplot(x=x, y=y, width=width, native_scale=True)
-        for i, bar in enumerate(ax.patches):
+        for bar in ax.patches:
             assert bar.get_width() == (width * 2)
 
+    def test_width_spaced_categories(self):
+
+        ax = barplot(x=["a", "b", "c"], y=[4, 5, 6])
+        barplot(x=["a", "c"], y=[1, 3], ax=ax)
+        for bar in ax.patches:
+            assert bar.get_width() == pytest.approx(0.8)
+
     def test_saturation_color(self):
 
         color = (.1, .9, .2)