Move polar border blanking to themeable

Author: iangow

plotnine/ggplot.py

@@ -520,11 +520,6 @@ def _draw_panel_borders(self):
         # grid lines below the borders. We leave ax.patch for the
         # background only.
         if self.theme.T.is_blank("panel_border"):
-            # For PolarAxes the default circular spine is separate from the
-            # panel border Rectangle; hide it explicitly when blank.
-            for ax in self.axs:
-                if "polar" in ax.spines:
-                    ax.spines["polar"].set_visible(False)
             return
 
         from matplotlib.patches import Rectangle

plotnine/themes/themeable.py

@@ -1711,6 +1711,11 @@ def blank_figure(self, figure: Figure, targets: ThemeTargets):
         for rect in targets.panel_border:
             rect.set_visible(False)
 
+    def blank_ax(self, ax: Axes):
+        super().blank_ax(ax)
+        if "polar" in ax.spines:
+            ax.spines["polar"].set_visible(False)
+
 
 class plot_background(themeable):
     """

tests/test_theme.py

@@ -2,6 +2,7 @@
 
 import matplotlib as mpl
 import pytest
+from matplotlib import pyplot as plt
 from packaging import version
 
 from plotnine import (
@@ -34,6 +35,7 @@
     theme_xkcd,
 )
 from plotnine.data import mtcars
+from plotnine.themes.themeable import panel_border
 
 LT_MPL310 = version.parse(mpl.__version__) < version.parse("3.10")
 IS_CI = bool(os.environ.get("CI"))
@@ -111,6 +113,17 @@ def test_add_element_blank():
     assert theme3 == theme4  # blanking cleans the slate
 
 
+def test_blank_panel_border_hides_polar_spine():
+    th = panel_border(element_blank())
+    fig, ax = plt.subplots(subplot_kw={"projection": "polar"})
+
+    try:
+        th.blank_ax(ax)
+        assert not ax.spines["polar"].get_visible()
+    finally:
+        plt.close(fig)
+
+
 def test_element_line_dashed_capstyle():
     p = ggplot(mtcars, aes(x="wt", y="mpg")) + theme(
         panel_grid=element_line(