Fix start-angle rotation hiding bars for full-circle plots

coord_polar hardcoded x limits to [0, 2π], but _to_radians maps data
to [start, start+2π]. With start=3π/2 the bars from ~Oct–Mar land at
theta > 2π and get clipped by the xlim. Fix by setting limits to
[start, start+2π] so the data range always falls within the visible
window. Remove the now-redundant break-wrapping mod-2π in coord_radial
since breaks in [start, start+2π] are naturally within the new limits.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: iangow

plotnine/coords/coord_polar.py

@@ -82,12 +82,14 @@ def setup_panel_params(
 
         empty = np.array([], dtype=float)
 
-        # x → theta axis: PolarAxes expects radians in [0, 2π]; suppress ticks
-        # because our data ticks would be in original data units, not radians.
+        # x → theta axis: data ticks are in original units (not radians), so
+        # suppress them.  Limits span [start, start+2π] so that bars rotated
+        # by a non-zero start angle stay within the displayed theta range.
+        theta_start = float(self.start)
         new_x = replace(
             pv_exp.x,
-            limits=(0.0, 2 * np.pi),
-            range=(0.0, 2 * np.pi),
+            limits=(theta_start, theta_start + 2 * np.pi),
+            range=(theta_start, theta_start + 2 * np.pi),
             breaks=[],
             minor_breaks=empty,
             labels=[],

plotnine/coords/coord_radial.py

@@ -160,12 +160,6 @@ def setup_panel_params(self, scale_x: scale, scale_y: scale) -> panel_view:
                 keep = [arc_lo <= r <= arc_hi for r in radian_pos]
                 radian_pos = [r for r, k in zip(radian_pos, keep) if k]
                 theta_labels = [l for l, k in zip(theta_labels, keep) if k]
-            else:
-                # Full circle: ax.set_xticks with negative values silently extends
-                # xlim below 0, turning the full circle into a partial arc.  Wrap
-                # all break positions into [0, 2π] to avoid this.
-                tau = 2.0 * np.pi
-                radian_pos = [r % tau for r in radian_pos]
             x_updates["breaks"] = radian_pos
             x_updates["labels"] = theta_labels