Error on bad input to hexbin extents

dstansby · dstansby · commit 928e58c4d8ca · 2024-01-09T13:19:22.000Z
diff --git a/lib/matplotlib/axes/_axes.py b/lib/matplotlib/axes/_axes.py
@@ -4999,6 +4999,10 @@ def reduce_C_function(C: array) -> float
             ty = np.log10(ty)
         if extent is not None:
             xmin, xmax, ymin, ymax = extent
+            if xmin > xmax:
+                raise ValueError("In extent, xmax must be greater than xmin")
+            if ymin > ymax:
+                raise ValueError("In extent, ymax must be greater than ymin")
         else:
             xmin, xmax = (tx.min(), tx.max()) if len(x) else (0, 1)
             ymin, ymax = (ty.min(), ty.max()) if len(y) else (0, 1)
diff --git a/lib/matplotlib/tests/test_axes.py b/lib/matplotlib/tests/test_axes.py
@@ -962,6 +962,18 @@ def test_hexbin_extent():
     ax.hexbin("x", "y", extent=[.1, .3, .6, .7], data=data)
 
 
+def test_hexbin_bad_extents():
+    fig, ax = plt.subplots()
+    data = (np.arange(2000) / 2000).reshape((2, 1000))
+    x, y = data
+
+    with pytest.raises(ValueError, match="In extent, xmax must be greater than xmin"):
+        ax.hexbin(x, y, extent=(1, 0, 0, 1))
+
+    with pytest.raises(ValueError, match="In extent, ymax must be greater than ymin"):
+        ax.hexbin(x, y, extent=(0, 1, 1, 0))
+
+
 @image_comparison(['hexbin_empty.png'], remove_text=True)
 def test_hexbin_empty():
     # From #3886: creating hexbin from empty dataset raises ValueError
