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

tools/triage_tests.py

@@ -254,7 +254,7 @@ def __init__(self, path, root, source):
         self.expected_display = f'{basename}-expected{display_extension}.png'
         self.generated_display = f'{basename}{display_extension}.png'
         self.name = self.reldir / self.basename
-        self.destdir = self.get_dest_dir(self.reldir)
+        self.destdir = self.get_dest_dir()
 
         self.thumbnails = [
             self.generated_display,
@@ -272,16 +272,21 @@ def __init__(self, path, root, source):
         else:
             self.status = 'unknown'
 
-    def get_dest_dir(self, reldir):
+    def get_dest_dir(self):
         """
         Find the source tree directory corresponding to the given
         result_images subdirectory.
         """
+        expected = self.root / self.reldir / self.expected
+        if expected.is_symlink():
+            path = expected.readlink().parent
+            if path.is_dir():
+                return path
         for baseline_dir in BASELINE_IMAGES:
-            path = self.source / baseline_dir / reldir
+            path = self.source / baseline_dir / self.reldir
             if path.is_dir():
                 return path
-        raise ValueError(f"Can't find baseline dir for {reldir}")
+        raise ValueError(f"Can't find baseline dir for {self.reldir}")
 
     @property
     def display(self):