Merge pull request matplotlib#22748 from meeseeksmachine/auto-backport-of-pr-22628-on-v3.5.x

Backport PR matplotlib#22628 on branch v3.5.x (Add RuntimeWarning guard around division-by-zero)

Author: QuLogic

lib/mpl_toolkits/mplot3d/proj3d.py

@@ -14,14 +14,18 @@ def _line2d_seg_dist(p1, p2, p0):
     p0[1] = y(s)
 
     intersection point p = p1 + u*(p2-p1)
-    and intersection point lies within segment if u is between 0 and 1
+    and intersection point lies within segment if u is between 0 and 1.
+
+    If p1 and p2 are identical, the distance between them and p0 is returned.
     """
 
-    x21 = p2[0] - p1[0]
-    y21 = p2[1] - p1[1]
     x01 = np.asarray(p0[0]) - p1[0]
     y01 = np.asarray(p0[1]) - p1[1]
+    if np.all(p1 == p2):
+        return np.hypot(x01, y01)
 
+    x21 = p2[0] - p1[0]
+    y21 = p2[1] - p1[1]
     u = (x01*x21 + y01*y21) / (x21**2 + y21**2)
     u = np.clip(u, 0, 1)
     d = np.hypot(x01 - u*x21, y01 - u*y21)

lib/mpl_toolkits/tests/test_mplot3d.py

@@ -1001,6 +1001,16 @@ def test_lines_dists():
     ax.set_ylim(0, 300)
 
 
+def test_lines_dists_nowarning():
+    # Smoke test to see that no RuntimeWarning is emitted when two first
+    # arguments are the same, see GH#22624
+    p0 = (10, 30)
+    p1 = (20, 150)
+    proj3d._line2d_seg_dist(p0, p0, p1)
+    p0 = np.array(p0)
+    proj3d._line2d_seg_dist(p0, p0, p1)
+
+
 def test_autoscale():
     fig, ax = plt.subplots(subplot_kw={"projection": "3d"})
     ax.margins(x=0, y=.1, z=.2)