Backport PR matplotlib#30243: Fix FancyArrow rendering for zero-length arrows

Author: nrnavaneet

lib/matplotlib/patches.py

@@ -1515,7 +1515,7 @@ def _make_verts(self):
             length = distance
         else:
             length = distance + head_length
-        if not length:
+        if np.size(length) == 0:
             self.verts = np.empty([0, 2])  # display nothing if empty
         else:
             # start by drawing horizontal arrow, point at (0, 0)

lib/matplotlib/tests/test_patches.py

@@ -999,3 +999,9 @@ def test_set_and_get_hatch_linewidth(fig_test, fig_ref):
 
     assert ax_ref.patches[0].get_hatch_linewidth() == lw
     assert ax_test.patches[0].get_hatch_linewidth() == lw
+
+
+def test_empty_fancyarrow():
+    fig, ax = plt.subplots()
+    arrow = ax.arrow([], [], [], [])
+    assert arrow is not None