FIX: short-circuit the contour changed call when uninitialized

greglucas · greglucas · commit 2c599356fd41 · 2021-02-21T16:18:57.000-07:00
The Quadcontourset.changed() method assumes some attributes to
be there. If we called changed from a parent class, the object
may not have been initialized with those attributes yet, so
skip that portion of the update.
diff --git a/lib/matplotlib/contour.py b/lib/matplotlib/contour.py
@@ -1027,6 +1027,10 @@ def _make_paths(self, segs, kinds):
             return [mpath.Path(seg) for seg in segs]
 
     def changed(self):
+        if not hasattr(self, "cvalues"):
+            # Just return after calling the super() changed function
+            cm.ScalarMappable.changed(self)
+            return
         # Force an autoscale immediately because self.to_rgba() calls
         # autoscale_None() internally with the data passed to it,
         # so if vmin/vmax are not set yet, this would override them with
