MNT: Check the input sizes of regular X,Y in pcolorfast

timhoffm · timhoffm · commit d55575ee34ad · 2024-09-20T15:17:32.000+02:00
Closes #28059.
diff --git a/lib/matplotlib/axes/_axes.py b/lib/matplotlib/axes/_axes.py
@@ -6634,6 +6634,15 @@ def pcolorfast(self, *args, alpha=None, norm=None, cmap=None, vmin=None,
                 if x.size == 2 and y.size == 2:
                     style = "image"
                 else:
+                    if x.size != nc:
+                        raise ValueError(
+                            f"Length of X ({x.size}) does not match the number of "
+                            f"columns in C ({nc})")
+                    if y.size != nr:
+                        raise ValueError(
+                            f"Length of Y ({y.size}) does not match the number of "
+                            f"rows in C ({nr})"
+                        )
                     dx = np.diff(x)
                     dy = np.diff(y)
                     if (np.ptp(dx) < 0.01 * abs(dx.mean()) and
diff --git a/lib/matplotlib/tests/test_axes.py b/lib/matplotlib/tests/test_axes.py
@@ -6626,6 +6626,27 @@ def test_pcolorfast_bad_dims():
         ax.pcolorfast(np.empty(6), np.empty((4, 7)), np.empty((8, 8)))
 
 
+def test_pcolorfast_regular_xy_incompatible_size():
+    """
+    Test that the sizes of X, Y, C are compatible for regularly spaced X, Y.
+
+    Note that after the regualar-spacing check, pcolorfast may go into the
+    fast "image" mode, where the individual X, Y positions are not used anymore.
+    Therefore, the algorithm had worked with any regularly number of regularly
+    spaced values, but discarded their values.
+    """
+    fig, ax = plt.subplots()
+    with pytest.raises(
+            ValueError, match="Length of X (5) does not match the number of "
+                              "columns in C (20)"):
+        ax.pcolorfast(np.arange(5), np.arange(10), np.random.rand(10, 20))
+
+    with pytest.raises(
+        ValueError, match="Length of Y (5) does not match the number of "
+                          "rows in C (10)"):
+        ax.pcolorfast(np.arange(20), np.arange(5), np.random.rand(10, 20))
+
+
 def test_shared_scale():
     fig, axs = plt.subplots(2, 2, sharex=True, sharey=True)
 
